Over the years I have heard this noise in different amps. My Techs in the past said there was nothing wrong. Until it starts on fire. They don`t always burn up, but I have had them smoke and throw sparks. And it is usually pretty bad. I have been able to repair some stuff over the years, but I am not educated beyond what I figured out myself. Now that I am old, it seems I can`t figure anything out. I have known some great Techs in my day, but they are all gone. I remember telling people about this noise and they would look at me funny. I could tell the way it sounded there was something wrong. I have never seen it put straight forward the way you have in this video. So, I was right when I heard the noise. If you didn`t have enough to work to do before, this video will get you a lot more work. I have many pieces of this old stuff and now I am going to hook them up one at a time. Thanks for this great video and I need your address so I can send you a truck load. Thanks
the more we can work it out to upcycle and keep things going longer, the better. consider the heap of e waste bc everyone wants perfect gear perfect sound perfect tv resolution. none of that is good in the long run for humanity / ecology. your channel is great bc it helps ppl understand more and learn that it’s not too terrible to fix these state of the art / amp pieces.
Well said! The wonderful thing about vintage audio equipment is that it was engineered/manufactured well and was made to be serviced when something failed. The parts(mostly) to repair these units are still available. The documentation to repair this equipment is available. The most difficult issue in todays world is finding a technician that can work on these things if you can't do it yourself. As time has gone on retirement and death have taken many of them.
Glad to see a new video from you. I just started getting into vintage audio repair when my Kenwood KA-7300 died in January. Your videos have been so helpful in my learning journey. Yes, I fixed it, and yes it's doing great! I also just got a KA-3500 after seeing your video on it. Hope to see more!
Glad to see that you are still above ground and seem to be doing well. Clearly I was not that only one that had concerns about you Chris. Looking forward to your next video.
Really useful video. I have just started trying to learn to fix old 7Os gear as a hobby and have been diligently measuring DC offset at the speaker outputs, but I never thought of it as a dynamic issue. There was either a problem at a single measurement or there wasnt. This vid has been extremely useful. I've currently got a Sansui Ba-f1 power amp which has started going into protection after a few minutes running. It was fine till I started moving boards about to access the coupling caps for Esr measurement, so I have almost certainly messed something up. Sigh. Will revisit it after I replace all those pesky Black Flag caps with new silver mica.
Thanks a lot for watching. It's great that you have got into fixing the equipment. It's a fun hobby and with less and less of the old technicians around many folks have to try and fix their own equipment.
@@jesse75Pretty sure I got them from a site called Hifi Collective in the UK. Recapping that amp was a disaster. The through holes were too small for modern caps and enlsrging them led to carnàge with pads and traces and that led to shorts and damage. Im still trying to get it running properly. Im a bit more competent now, but I made every mistake in the book.
Hello Chris.... Happy to see a new video from you... I always enjoy your content... wish you were in Ohio .. I would love to hang out and talk audio, listen to music....!!! I have a couple of friends in Lexington Ky... we get together once in awhile.... but I don't know anyone like you & your knowledge, expertise.... Please keep up the good work it is greatly appreciated ❤
My question as well. i have a pair of Adcom 555's, a Carver M-500 and recently, a NAD 208thx. All of them are 200+wpc, and the speakers I would use with them are a pair of aDs L810s or the 910s, both of which are 1970's era speakers. I'd hook up some 8ohm bookshelves to test first though.
You should have a positive and negative speaker terminal for each channel on your receiver/amp. You should have two leads from your meter. Polarity doesn't matter in this case but if you want you can attach the positive meter lead to the positive terminal on you receiver/amp. The negative to negative. DON'T SHORT THEM TOGETHER!
Purchased my H.K. 730 Twin in 1977 paired with JBL l100 still sounds good too me.but of course ive aged going on 48 years and im sure if i tested it like you do, some things will probably have to be updated.great video & its probably time to give it a tune up.
Looking forward to the repair on this one. I have a Pioneer surround sound receiver that is 32 years old and having the right channel cut out after it's been on awhile. The left is starting to do it too a little. No relay clicks>>the sound just stops. Occasionally if I tweak the volume, it will come back on. There is no-one in my area that does service these days. Repair places are getting hard to find so I have to learn to do it myself.
Aha the return of one of the original greats of audio repair. Good to see you back , highlighting that DC offset isn't a measure one time and its done issue ( guilty). Just learning from these videos is a pleasure & important as tech skills becoming impossible to find . Thanks for passing the knowledge
Well....the rule is.... For direct coupled amps like this SA-9900 and many other amps/receivers, no speakers attached. For cap coupled amps/receivers, speakers or load resistors attached. Frankly for a unit like this SA-9900 attached or unattached is fine. It reads the same. Always safer to test any unknown amp/receiver without speakers. No chance to damage the speakers if there is an issue.
DC offset is a neglected corner of amplifier troubleshooting and repair. In a past life I serviced many different amplifiers, if I did not see a stable 20mV or less, further investigation reqd. Often in DC coupled amps the problem was right at the front of PA section, the matched pair in differential configuration had drifted with age, and the error was literally amplified. Sometimes capacitor issues and simple dry joints contributed also. Good graph and explanation.
Have you ever worked on a nakamichi 5 channel amplifier ? Mine stopped working the light still comes on , I've repaired some electronics before but this thing might be beyond my abilities , I guess I will just start with the oblivious stuff 🤔 I think my Crossover may have shorted out cause the issue
I’ve still got the audio gear I bought about a million years ago in the Frankfurt PX & Mx Kastel audio club. After 40 years the pots are getting as scratchy as I am. Lol. That’s all I hope I need is someone who can clean all the contacts. I wish there was someone who could restencile my DBX CX-3. 40 years of regular use has worn the white paint off the black plastic face.
Chris, I have a question for you. Should I keep my old equipment on a shelf in the garage or should I have it out and regularly played? I hope problems don't develop while in storage.
You can store them for sometime but it's good if you can power up the gear every year or two. Just to charge up the electrolytic capacitors. You don't even have to hook them up and play music. Just plug them in and let them sit on for a few hours.
The three main problems I encounter when repairing vintage audio gear from this era is number one dirty switches number two dirty potentiometers and number three the DC balance is out of adjustment but not enough to cause the protection circuit to kick in.
@@joerosen5464 Technically, these receivers aren't in need of repair, or the replacement of parts. They are in need of adjustment and maintenance to restore function of the pots.
You would need the service manual for your unit or find the information on the net. In addition you would have open up the unit which puts both you and your equipment in danger.
Got an old timer named 'Doc' local here (old timer, yeah . . . I'm 70) and I took in a Marantz made in 1978 for a good going over. Thing worked fine after DeOxit and replacing all the bulbs which I did before taking it in.. Got a call the same day and Doc said, 'Don't need nothing.' Hooked it up and set up the voltmeter and dead Zero offset DC. 'Everything works to spec,' he said. I use the receiver everyday . . . sweet.
If he didn't replace any electrolytic capacitors, then he didn't give it a "good going over". That's what's called a cursory going over, of the sort a trained monkey can perform. Your Doc is a Quack!🐂
Where does the damage occur in speakers when multiple dc volts are sent to it? Is it the voice coil of the drivers or the crossover or something else? And what happens to those parts when this type of damage happens?
@@vintageaudioaddict , Thanks for the info, good to know. I was wondering as I measured some sending some significant dc voltage coming out of an amp I was using to power an old altec compression drivers of mine some years ago that are now in storage. The good news is the voice coils are connected to the diaphragm and they are easily replaced and still readily available. Also good that the amp was only powering the compression drivers as the amp was part of an active crossover system.
Also he's talking about a 1975 unit. I've had problems with 20 year old amps. The newer amps can sound boring and flat and may be a waste of money - if you don't want to listen to it.
@@stevenvox6549And the older ones like a Fry-An-Ear SA-9900 sound better, even when completely recapped, cleaned, & gone through input to output? I hate to break it to y'all, but this is mass-produced Japanese mid-fi that nobody in the company ever listened to before they shipped any of them out of their doors, EVER. Can't say that I agree with you that this old mid-fi junk, designed solely by test equipment measurements by a faceless committee of po-faced Japanese Engineers whose sole concern was earning their retirement pensions from the giant conglomerate that employed them, is somehow better sounding than newer stuff! I suggest that you check out the next Hi-Fi show near you when one comes up...
I appreciate it the way you explain things to the common man not somebody that's advanced in electronics. I just have a lower knowledge of electronics so it's very helpful to keep things simple. I would appreciate any other practical video tips.
My problem (and I consider it to be huge) is my Kenwood KR8050, which I bought new has started acting up and I can’t find anyone around here (north Carolina) who will do a complete overhaul with new caps and transistors where needed as well as a cursory cleaning (unit is very clean physically) and do all the proper testing to give it back to me working great. I bought this new back in 1979 and it cost me more than a few meals but I loved the sound and have never looked back. I’m heartbroken that it has started cutting out and just plain stopped working for certain things. I won’t sell it and I will ship it for repair but only if I can believe they will do a good job. I’m thinking of moving to where people can actually do stuff like this.
First of all your Kenwood is a fine receiver and it's great that you have had her all of these years. I have the exact same model as you in my collection. It's tough to find folks anymore who you can trust working on this equipment. As the equipment has got older so have the folks who use to work on it. The technicians are just disappearing. Do a google search and see if there is anyone within a hundred miles or so from you that could help. That way you could just take it and pick it up yourself. Shipping this equipment is expensive and you have to pack it like it's going to the moon to arrive safe. Good luck finding someone.
I have a Pyle, the one made from China (2016 era), 4 channel car amp and it was sending many volts (Not sure what it was but knew it was wrong) to the front speakers damaging them. I have not repaired it, but was guessing a shorted capacitor since it looks like this model uses some of them between the output transistors and the the speaker. Now I wonder if one of the output transistors was failing. Still play normal when I tested it but seeing that voltage at the speaker connection is a problem. (Pyle used to be made in USA.)
@@Rob.DB. The Pyle speakers was were I first heard of Pyle. Then in the 1980's,1990's I saw they had some amps at a car stereo show/sale. Yet I recall telling a stereo shop about the Pyle amp and they said that Pyle did not make any amps. The only problem I had with their speakers, was the foam edge would go bad but that was the thing with most speakers of that time era. I did not know until much later, around 1996 that those foam edges could be replaced. I did that to my 12 inch woofers, then some other brand stuff later. Some people frown on the foam edge design, but it has less resistance, less weight, so it is more responsive then the rolled paper or the rubber. I think Quam was the first to come out with the foam edge for speakers. Now Quam stuff was more hype then quality. Nice foam edge but the 6 X 9 speakers were rated for like 5 watts. Another speaker I think was hype back in the 1990's; was Pyramid. High wattage but stiff as a board.
Just rebuilt an SX-737 and the DC offset was spastic, replacing the "shoot on sight" transistors on the TONE board with some KSA992 and KSC1845 and all is quiet. Pioneer was prescient in knowing what transistors were going to age poorly and used them a lot in this era.
spoiler alert........ It is a certain transistor type(2sc1451). That transistor is a known troublemaker in vintage audio equipment. Still alive and drinking daily. lol. Thanks for watching!
Some good info and advice. I have six vintage units, most never touched except offset and blown out occasionally. I suppose after 50 years of bliss there could be an issue. Or ...a few years of crap, then more crap, then more all in search of that 50 year old sound with newer junk....My truck will also need repair down the road.....still I use it....
Behringer KM750 750W 2-channel Power Amplifier and haven't looked back. Miss my Onkyo power amp but it just wasn't worth fixing. I did have to put a 12v Noctua 92mm case fan with a fan temperature controller and small 24v to 12v buck convertor, because the OEM fan was pretty loud and always ran at max speed. But there is a ton of space in the case. The fan now almost always runs at the minimum speed I set and is inaudible, when it does ramp (does it even) the music is so loud I still can't hear it. I am not an audiophile but I think I have a fairly discerning ear. I know it sounds great and much better than a worn out vintage amp.
The biggest thing I do not like about this vintage is they do NOT have banana plugs or 5 way binding post. You are supposed to thread a 14 gauge wire into a little hole.
They were designed according to the level of sound performance they offered. Good for the old boys who want to relive their lost youth, & maybe now that they're old & grey they can finally afford that big flashy piece of mass-produced Jap-Crap they lusted over but never were able to buy when their face still had pimples on it & their heads were fully covered with hair...Now all this 🫨🫤😕☹️🫣😱😵💫🥵-sounding 🦨💩🚮 mass-produced AUDIO DEATH is insanely collectable (or at least, insanely priced...🤡👺🤡) as folks first threw all this 🤮 in the tip where it sonically belongs, then stood around whilst rich Vietnamese guys bought up the rest of it to send by the container load for 🤑🤑🤑😎 to the ol' communist Homeland where they resell it for several multiples more than what they paid...And so now all those dime-a-dozen shiny faceplates are getting a bit rare! 🤔🧐 Vinyl FINALLY came back after all the same DUMMIES finally figured that Seedy sucks & that "Home Theatre" was nothing more than "💩y TV sound, only MUCH louder". So once EVERYONE ELSE started playing LP's again, mostly your kids, & all the REALLY good sounding vintage Tube gear had long disappeared (mostly to Asia as well, notably Japan & then Hong Kong) these same Japanese transistor radio connoisseurs found it socially acceptable to be seen playing their own LP collections...if they hadn't thrown all of them away by 1988... So the old component Hi-Fi set that's been sitting in the garage/attic/cellar unused for the last 30+ years gets dusted off because...why spend money to buy something that'll actually work & sound good the moment you plug it in? Why not risk setting your house & hair on fire & just plug it in & see if you can get the smoke hidden deep inside those old neglected fossils to come out for you? Are these the same guys who need big speaker wire connectors, too? If you're going to acknowledge that certain things, like wires & cable, are important; then you're admitting that certain things have moved ahead in the last 40+ years of Hi-Fi technology. Like sound quality, for instance.🤔 🤣🤣🤣 Otherwise, this trip isn't about sound quality; not that 98% of these vintage Japanese receiver collectors have developed any hearing acuity in the intervening decades. Otherwise they'd be going into Hi-Fi stores, the few bricks & mortar ones still left anyway, & buying stuff that not only sounds alot better but comes with a factory warranty & won't need a re-capping job until at least 2050. And the way prices are going, you can buy a brand-new Made-In-America-by-Americans top-of-the-line McIntosh or Mark Levinson for less money (and hassle, and grief) than a 45 year-old Marantz 2500 (or 50 year old Fry-An-Ear SA-9900...). This new stuff sounds about 100x better, works about 100x better, all the parts for them are still readily available & don't require a scavenger hunt on ePay for a transistor that was custom made for one model of Soundscrewy in 1976-77 (& will cost you $300, for a used one that's probably as blown up as the one that you're trying to replace, from some guy in Malaysia or Nigeria or Belarus). Oh, and the new stuff has noiseless switching, instead of requiring a steady diet of De-Oxit applied to its NON-REMOTE CONTROLLED front panel function selectors every 3 months or 3 hours of use (whichever one comes first). And best of all, has WELL-SPACED, HIGH-QUALITY RCA jacks & WELL-SPACED 5-way binding posts because the gear was designed & built for them, by people who ACTUALLY LISTENED TO THE DAMNED THING when they were designing it, as opposed to the faceless committee of tin-eared Japanese Engineers with jobs-for-life within their giant Japanese Keiretsu (Sansui & Luxman occasionally excepted) who just designed the unit to have better specs than last year's model & the new models from the giant keiretsu across the street, & the only one that ever actually listened to what they designed WAS YOU! 🤓🤖🙉🙉🙉
Sounds to me like this issue is either a possible loose connection in that pre-amp/power amp separation switch, which could be remedied with a good contact cleaner and lube, OR, it very well could also be caused by some leaky or even totally bad electrolytic capacitors somewhere in the circuit of this amp... In this one's case, probably somewhere within the pre-amp part of it, since disconnecting the two parts by flipping that switch seems to completely stop the noise... But I will look forward to seeing and watching your repair video for this amp to see what it actually was and how exactly you fixed this issue!
spoiler alert........ It is a certain transistor type(2sc1451). That transistor is a known troublemaker in vintage audio equipment. Thanks for watching!
@@Poppinwheeeeellllllieeeeez Hey, sometimes it's actually just as simple as that in fixing vintage audio gear! I've totally fixed used gear exactly that way MANY numerous times over the decades... Sometimes it actually IS something more difficult and expensive to replace, like proprietary components or discrete semiconductors, sometimes which are obsolete so they have to be substituted with something equivalent or as similar as possible, then the surrounding circuit be adjusted accordingly if necessary, but you always want to at least TRY the very cheapest and most BASIC things FIRST, BEFORE you automatically assume the absolute worst and just start throwing expensive or hard to find parts at something!... So not exactly a "noob" take on this topic, but thanks for your assuming that, because now that assumption actually just makes YOU seem like a "noob", because any really good tech or repair person should ALWAYS try the most simplest and basic things FIRST, before ever having to get into the replacing of actual semiconductors and such. You should know that too if you're REALLY into this sort of thing, so not to be mean at all, but just making it clear that my initial thoughts about this problem would still have been a good place to START at least, and THEN, if that basic stuff, (which should be done in ANY case, with a truly Good quality restore of vintage equipment), still didn't fix the issue, THEN you start checking ALL of the other components in the circuit!... After loose connections and bad caps, then semiconductors. The guy in this video probably did exactly that himself, unless maybe he ALREADY knew in advance to check that one specific transistor exclusively and first, maybe from prior experience with this specific amp model before, OR maybe he took a suggestion from an online repair forum or something?... But without knowing ANYTHING about what exactly is wrong with something, you always start with the very simplest, quickest, and easiest things to repair or replace first and foremost, then go from there. The fact that he said that it actually was a transistor that went bad is just a coincidence in this case, because I've heard noises exactly like what he showed in this video being caused by nothing more than loose connections in switches and/or from bad electrolytic caps in old vintage gear, more oftentimes than not, which is of course a super easy and (usually) cheap thing to fix, depending on what all else may be wrong with the equipment being restored. Anyway, have a good day, and let's both just look forward to this guy's follow up video to this one, showing exactly what all he had to do to get this beautiful amp working properly again!
I recently repaired a (not really vintage because it;'s from the 2000s) Yamaha RX-371V receiver that I had salvaged from Goodwill for about $10. It wasn't powering up, so I found the schematic and started probing. The unit has 2 transformers, a main one that powers the unit when it's on, and a standby transformer that powers the IR receiver and the power button circuitry. The secondary of the standby transformer wasn't outputting any voltage and the secondary was open circuit. I found in my stockpile of parts a suitable replacement (compatible voltage, larger rated power of 16W vs 5W the original, larger footprint too so I had to get a little creative to install it). After replacing that, the unit powers up and works great. The nagging question that remains in my head is: what could have caused that failure. I probed around the standby circuitry and everything checks out, no shorts, no bad caps etc. And I wonder how long until it fails again, this time maybe taking with it something else inside. But all in all for a $10 price tag, a spare transformer and a few hours of work, I'd say not bad.
would you please share with me what you are using the measure the voltage over time? Thanks. Maybe I should ask what is an economical way for me to make these measurements?
I just subscribed. I'm going to take an educated guess that this was a small signal transistor causing this issue. This is particularly nasty in direct coupled amplifiers where a complete failure of a small signal transistor can cause an output offset almost equal to one of the supply rails.
@@vintageaudioaddict you're most welovme regarding the sub. Cool channel. Those Japanese small signal transistors are as notorious as RIFA caps! Did they have the telltale black lead syndrome?
I’m not sure that would be correctly considered a DC off set issue. I could be wrong, but I equate an offset issue with a power amp imbalance between the rails. Not a power amp correctly responding to an input signal……which is what you ultimately have.
You could say that. The amplifier section was responding correctly to the signal it was receiving from the preamp section. The DC voltage speaker protection circuit responded correctly when the DC voltage being sent by the amplifier section to the speakers was high enough. Bottom line, everything worked correctly to save the speaker drivers.
So adjusting the DC offfset fixes these spike? Have my Marantz 2226 clicking after a couple of minutes of playing then it stops ? Sounds good though no static or distorted sound?
Even worse is: The "protection" circuit fails.I've seen a Cerwin-Vega 15 inch speaker catch on fire Sanyo 100w/per amplifier-actually I smelled it first then the speaker tried to leave the cabinet
What is the easiest way to graph the DC over time? What do I need beyond a DMM? I'm getting to the end now. I'll finish and hopefully will see the answer. So would a hold function be of use? Could it show the peaks?
You will need a DMM that you can hook up (usually via USB) to a computer and some software that usually comes with the meter. In my case the data you saw was captured by my Siglent SDM3045X and sent to my computer. I then recorded it using video capture software.(flashback express)
Thanks for watching. I'd checkout some videos. On UA-cam there are a lot of smart folks that are into electronics. Both basic electronic theory as well as others who work on the vintage electronics like myself. Most of it is not that difficult if someone shows you. With video's you can watch how something is done or how it operates.
My guesses on that would be switch cleaner on the PSU connectors in case one of the DC rails is causing the problem, and often you get a preset bias potentiometer to balance the op stage and they can get a bit corroded, so more switch cleaner. Finally I would resolder any PCB joints that might have cracked up due to thermal problems, e.g. WW resistors, OP transistors. If that failed another trick is to use freezer spray on individual components while measuring the offset.
@@vintageaudioaddictI am well. I have a modest amount of tools and meters but have brought a SX-727, a 2220 and a Yamaha C-60 back to life in the last few months. I am slowly immersing myself into the hobby. Mostly fixing stuff for others and occasionally for myself.
I had one such symptom, exactly this condition, in an active speaker, after approx half an hour started making huge noise and stops the useful signal. Was quite hard to repair, because of the way how was designed, with several boards (preamp, tone corrector, another preamp..) stacked parallel. Anyway, the defect was in the polypropilene/polyethilene capacitors (typical 1... 220nF) from these preamps, and I think there are more of them with that issue, cause after finding one on oscilloscope i kept getting the noise, a bit rarer, efectivly the symptom persisted so I decid to change them ALL, and after that only, the ampli was good.
A capacitor on My yamaha R-1000 receiver gave up the smoke while playing yesterday. I racapped it, but a transistor went bad. Waiting on parts to replace the transistors on the power supply board.
I had to stop the video a couple times where you pan across all that gear to confirm you show the same Luxman cassette deck that I've got. I have a bearing problem with the motor, sometimes it won't spin up.
So I did a measurement on a old Kenwood amp I just bought that is all original untouched never recapped and it sits at between 0.6 to 0.8mV is that good asking as I know my way around but not that well
Well, if it's really that low then yes that is great. Just make sure that you are measuring correctly. The correct scale on the meter and make sure that your speaker selector switch is set to the speaker outputs that you are measuring. Thanks for watching!
hey Chris, do you know what is going on with the hifiengine? i used to have an account but had to care for my elderly parents for a while so i was not able to be very active and they killed my account and now they do not allow me to create a new one! i am trying to power up again and have no idea why they killed my account. thanks 🙂
Other's have had that same experience. I've heard that they are disabling accounts that have not logged in for a while. What a while is?, I don't know. Also, they are not taking any new accounts for some reason. Again, I have no idea why.
@@vintageaudioaddict i can't even send them a message! if your account is still active, would you please send them my message and see if you can get some answers? if they need help, i can volunteer. i was a very active member but as i said, my parents came first 🙂
I had a Marantz top tier stereo amp. Very, very heavy. From late 1970s. Sat in storage for decades. Sounded great, except scratchy pots, when I fired it up about 2012. Then one day, it just would not turn on anymore. Threw it out.
I have an old pioneer amp that was sitting in the rain for days before i found it. It works but the solder is corroded and there's DC on the outputs. It even blew one of my tweeters. I know i need to fix it but I'm dreading disassembling it and cleaning every solder connection and replacing each component. For now i just let it run for a long time and let it warm up before i use it. Lol
Good video. It is hard to get people to understand there may be problems below the surface. Working-Good! Not working-Bad! btw what is the stereo in the thumbnail?
Hey man! Great channel u have here! Iused to fix antique radios Still have a Radiola 60 and its wrkg . Woul really like to know more bout my Sx850 and 950. And kenwood 6600 as aux input ia a dogs dinner. The 8 and 950 are great rcvrs, kenwood 6030 has lots of beef. Yup ill be watching you .lots of rcvrs have the jumper pins. Have even seen rcvrs being sold with out them.
When you don't hear any crackles and pops, its sometimes best to attach a dummy loaded resistor of the correct impedance value and then measure the speaker output across each terminal with the resistor attached, that way you'll be able to see what kind of signal your speakers are receiving. That's the way i do it, firstly without & then with a resistor.
Hi Chris, and wider audio community. Not sure if the topic of this video is what I'm experiencing but I have an old Denon PMA-350SE. Quite randomly during usual low volume use it would suddenly jump up to max volume static horrid noises, only way to stop it was to turn it off. Often it would then be fine when turning it back on for a somewhat random amount of time before doing it again, it was fairly inconsistent. I haven't used it for a while now because it was honestly quite shocking/painful when it would bug out like this. Wondering if this is a common issue you might be able to identify from this brief description? Cheers for any help.
for abnormal dc offset ,the first thing is, always check variable resistor or trimpot of dc offset setting and bias in vintage amps. and then leaky bjt
I have a Sansui 5050 receiver that went totally silent while listening to music.Checked all the internal fuses, they are all ok. Is there a obvious component failure that would cause dead silence while power is on.Unit lights up ,no sound.
It's tough to say. If it's all the inputs, It could be in the power supply section, protection circuit or the amplifier section that caused the protection circuit to operate. Sorry that I can't diagnose exactly what your issue may be.
I was just working on mine and if you open the unit towards the left is a preamp board? with a pin connector on top with 3 wires I believe. I removed this board and the top pin connector and cleaned the contacts with Deoxit. Reinstalled the board (snaps into place) and the dead channel came back to life.
Do you have a Sansui 5050? Both channels are out.,No sound.There isn't an intermittent problem that would indicate a dirty contact.Unit lights up ,no sound.@@68wrko
This is the voice of Thom Shane from the Shane Company who used to sell diamonds in Seattle. Somebody out there knows what I'm talking about but I have been trying to remember where I heard your voice before and it's a dead ringer
I think this is most likely due to a flakey dielectric in an electrolytic cap. With old gear, it's always a good idea to replace all the electrolytics. Even a cap that tests OK regarding leakage & ESR, may crap out soon. For tube equipment, it may have those wax-impregnated paper ones, and they should be replaced, too. Then, it's always a good idea to check & adjust the bias currents. The service manual (available for most old gear) will give instructions. Other possible causes of the problem are, dirty switches/pots (clean & lube), cold solder joint (find by tapping with a plastic screwdriver handle, around the PCB, or just resolder them all), and a noisy transistor (locate with "freeze spray"). Of course, you can fire up the 'scope, and track the problem down. So you say you're not an electronics technician? Then become one! There's nothing like an avid interest in a subject to motivate study.
IDK. I’m still running (bridged) Carver TFM-45’s mated to Sony TA-E9000ES Processor and my ol’ school Polk 1.2tl SDS-SRAs and Velodyne FSR15s (x2) still image as they did from the day I first purchased everything. Granted, every 10 yrs I replace the Polk drivers and tweeters, and the Carver’s had new caps, etc. installed 5 yrs ago. I will NEVER part with my gear!!
Over the years I have heard this noise in different amps. My Techs in the past said there was nothing wrong. Until it starts on fire. They don`t always burn up, but I have had them smoke and throw sparks. And it is usually pretty bad. I have been able to repair some stuff over the years, but I am not educated beyond what I figured out myself. Now that I am old, it seems I can`t figure anything out. I have known some great Techs in my day, but they are all gone. I remember telling people about this noise and they would look at me funny. I could tell the way it sounded there was something wrong. I have never seen it put straight forward the way you have in this video. So, I was right when I heard the noise. If you didn`t have enough to work to do before, this video will get you a lot more work. I have many pieces of this old stuff and now I am going to hook them up one at a time. Thanks for this great video and I need your address so I can send you a truck load. Thanks
Thanks for sharing. I just recently rebuilt my SX-1250... Caps galore, and many transistors and diodes. Big improvement, and it's much healthier now.
Good decision to do the work on your SX-1250. She will now be good to go for another lifetime. Thanks for sharing your rebuild.
@@vintageaudioaddict Fortunately I've learned enough to build kit amps, and have some really neat stuff... like a 300b tube amp.
Where did you get the parts ?
excellent video , looking forward to the follow up trouble shooting and repair.
the more we can work it out to upcycle and keep things going longer, the better. consider the heap of e waste bc everyone wants perfect gear perfect sound perfect tv resolution. none of that is good in the long run for humanity / ecology. your channel is great bc it helps ppl understand more and learn that it’s not too terrible to fix these state of the art / amp pieces.
Well said! The wonderful thing about vintage audio equipment is that it was engineered/manufactured well and was made to be serviced when something failed. The parts(mostly) to repair these units are still available. The documentation to repair this equipment is available. The most difficult issue in todays world is finding a technician that can work on these things if you can't do it yourself. As time has gone on retirement and death have taken many of them.
Within the chaos of the world it's awesome to hear you're still out there. Hope all is well and look forward to more content if possible.
Thanks for checking in. Yes, all is well here. Hopefully all is well on your end also.
Glad to see a new video from you. I just started getting into vintage audio repair when my Kenwood KA-7300 died in January. Your videos have been so helpful in my learning journey. Yes, I fixed it, and yes it's doing great! I also just got a KA-3500 after seeing your video on it. Hope to see more!
Thank you so much for watching! Great job on your repair! Kenwood made some great gear back in the day.
LOL. I remember selling that equipment in 1977. I wish I had known how valuable the monster receivers would become.
Where did you get the parts ?
Glad to see that you are still above ground and seem to be doing well. Clearly I was not that only one that had concerns about you Chris. Looking forward to your next video.
Thanks a lot for checking in. Ya, still kicking and all is well. Hopefully the same on your end.
Really useful video. I have just started trying to learn to fix old 7Os gear as a hobby and have been diligently measuring DC offset at the speaker outputs, but I never thought of it as a dynamic issue. There was either a problem at a single measurement or there wasnt. This vid has been extremely useful.
I've currently got a Sansui Ba-f1 power amp which has started going into protection after a few minutes running. It was fine till I started moving boards about to access the coupling caps for Esr measurement, so I have almost certainly messed something up. Sigh.
Will revisit it after I replace all those pesky Black Flag caps with new silver mica.
Thanks a lot for watching. It's great that you have got into fixing the equipment. It's a fun hobby and with less and less of the old technicians around many folks have to try and fix their own equipment.
Where did you get the parts ?
@@jesse75Pretty sure I got them from a site called Hifi Collective in the UK.
Recapping that amp was a disaster. The through holes were too small for modern caps and enlsrging them led to carnàge with pads and traces and that led to shorts and damage. Im still trying to get it running properly.
Im a bit more competent now, but I made every mistake in the book.
Hello Chris.... Happy to see a new video from you... I always enjoy your content... wish you were in Ohio .. I would love to hang out and talk audio, listen to music....!!! I have a couple of friends in Lexington Ky... we get together once in awhile.... but I don't know anyone like you & your knowledge, expertise....
Please keep up the good work it is greatly appreciated ❤
How do you connect to the speaker outputs? Where does the ground wire go, to the chassis or on the speaker ground where the speaker wires artach?
My question as well. i have a pair of Adcom 555's, a Carver M-500 and recently, a NAD 208thx. All of them are 200+wpc, and the speakers I would use with them are a pair of aDs L810s or the 910s, both of which are 1970's era speakers. I'd hook up some 8ohm bookshelves to test first though.
You should have a positive and negative speaker terminal for each channel on your receiver/amp. You should have two leads from your meter. Polarity doesn't matter in this case but if you want you can attach the positive meter lead to the positive terminal on you receiver/amp. The negative to negative. DON'T SHORT THEM TOGETHER!
@@vintageaudioaddict Thank you, Sir Vintage! Oh, and I know to select DC, not AC on the meter, but if a reader doesn't...now you do!
Thank you!@@vintageaudioaddict
Purchased my H.K. 730 Twin in 1977 paired with JBL l100 still sounds good too me.but of course ive aged going on 48 years and im sure if i tested it like you do, some things will probably have to be updated.great video & its probably time to give it a tune up.
Glad to have you back Chris
Thank you!
Really informative, Thanks! And what a beautiful amplifier on the turntable. 70s and 80s had style...
Glad you enjoyed it! Yes, the old vintage gear was/is special.
Looking forward to the repair on this one. I have a Pioneer surround sound receiver that is 32 years old and having the right channel cut out after it's been on awhile. The left is starting to do it too a little. No relay clicks>>the sound just stops. Occasionally if I tweak the volume, it will come back on. There is no-one in my area that does service these days. Repair places are getting hard to find so I have to learn to do it myself.
Aha the return of one of the original greats of audio repair. Good to see you back , highlighting that DC offset isn't a measure one time and its done issue ( guilty). Just learning from these videos is a pleasure & important as tech skills becoming impossible to find . Thanks for passing the knowledge
Do you check the offset with the speakers attached?
Well....the rule is.... For direct coupled amps like this SA-9900 and many other amps/receivers, no speakers attached. For cap coupled amps/receivers, speakers or load resistors attached. Frankly for a unit like this SA-9900 attached or unattached is fine. It reads the same. Always safer to test any unknown amp/receiver without speakers. No chance to damage the speakers if there is an issue.
@@vintageaudioaddict My 1985 Yamaha A1000 is measuring a steady 4.5mv.
@@vintageaudioaddict One might keep SOME kind of load on a tube output amp.Or is that poor thinking?
DC offset is a neglected corner of amplifier troubleshooting and repair. In a past life I serviced many different amplifiers, if I did not see a stable 20mV or less, further investigation reqd. Often in DC coupled amps the problem was right at the front of PA section, the matched pair in differential configuration had drifted with age, and the error was literally amplified. Sometimes capacitor issues and simple dry joints contributed also. Good graph and explanation.
Have you ever worked on a nakamichi 5 channel amplifier ? Mine stopped working the light still comes on , I've repaired some electronics before but this thing might be beyond my abilities , I guess I will just start with the oblivious stuff 🤔 I think my Crossover may have shorted out cause the issue
Where does a person get parts ?
I’ve still got the audio gear I bought about a million years ago in the Frankfurt PX & Mx Kastel audio club. After 40 years the pots are getting as scratchy as I am. Lol. That’s all I hope I need is someone who can clean all the contacts. I wish there was someone who could restencile my DBX CX-3. 40 years of regular use has worn the white paint off the black plastic face.
Does the Volume control position affect this measurement?
No, not with the issue that I had with this unit.
Chris, I have a question for you. Should I keep my old equipment on a shelf in the garage or should I have it out and regularly played? I hope problems don't develop while in storage.
You can store them for sometime but it's good if you can power up the gear every year or two. Just to charge up the electrolytic capacitors. You don't even have to hook them up and play music. Just plug them in and let them sit on for a few hours.
hey there. ok you did more than explain but how do you fix it?
In this SA-9900 the fix was to replace the 2SC1451 transistors in the entire unit. They are known troublemakers.
Great to see you back Chris ! and with good info and tips as always. Thank you Sir.
Thank You!
The three main problems I encounter when repairing vintage audio gear from this era is number one dirty switches number two dirty potentiometers and number three the DC balance is out of adjustment but not enough to cause the protection circuit to kick in.
Thanks for sharing.
Then you're not actually repairing it, are you?
@@joerosen5464 Technically, these receivers aren't in need of repair, or the replacement of parts. They are in need of adjustment and maintenance to restore function of the pots.
Thanks, this is great technical info. Appreciated!
Glad it was helpful!
great vid but i still have no clue how to adjust DC offset if needed…?
You would need the service manual for your unit or find the information on the net. In addition you would have open up the unit which puts both you and your equipment in danger.
Got an old timer named 'Doc' local here (old timer, yeah . . . I'm 70) and I took in a Marantz made in 1978 for a good going over. Thing worked fine after DeOxit and replacing all the bulbs which I did before taking it in..
Got a call the same day and Doc said, 'Don't need nothing.' Hooked it up and set up the voltmeter and dead Zero offset DC. 'Everything works to spec,' he said. I use the receiver everyday . . . sweet.
If he didn't replace any electrolytic capacitors, then he didn't give it a "good going over".
That's what's called a cursory going over, of the sort a trained monkey can perform. Your Doc is a Quack!🐂
As new to your channel I am catching up. I loved the intro seeing all Those vu meters from the past! Few of those beasts in my workshop!
Thanks so much for finding the channel!
What did you connect the multimeter to ‽ Would help if you had showed that for us newbes. Thanks!
He said a couple times " to the speaker output " either right or left will do.
Where does the damage occur in speakers when multiple dc volts are sent to it? Is it the voice coil of the drivers or the crossover or something else? And what happens to those parts when this type of damage happens?
Yup, the voice coil will heat up and fail.
@@vintageaudioaddict , Thanks for the info, good to know. I was wondering as I measured some sending some significant dc voltage coming out of an amp I was using to power an old altec compression drivers of mine some years ago that are now in storage. The good news is the voice coils are connected to the diaphragm and they are easily replaced and still readily available. Also good that the amp was only powering the compression drivers as the amp was part of an active crossover system.
Great video. This problem is very common in units with the "famous noisy" japanese transistors 2SA726 and 2SC1451 probably causing the problem.
Also he's talking about a 1975 unit. I've had problems with 20 year old amps. The newer amps can sound boring and flat and may be a waste of money - if you don't want to listen to it.
@@stevenvox6549And the older ones like a Fry-An-Ear SA-9900 sound better, even when completely recapped, cleaned, & gone through input to output? I hate to break it to y'all, but this is mass-produced Japanese mid-fi that nobody in the company ever listened to before they shipped any of them out of their doors, EVER.
Can't say that I agree with you that this old mid-fi junk, designed solely by test equipment measurements by a faceless committee of po-faced Japanese Engineers whose sole concern was earning their retirement pensions from the giant conglomerate that employed them, is somehow better sounding than newer stuff! I suggest that you check out the next Hi-Fi show near you when one comes up...
Are you measuring this open circuit or do you have a dummy load on the output?
I didn’t understand a dam thing but I ended up watching the whole video ;)
Thank you for watching!
That makes two of us!😂
Black leg transistors most likely. Could also be bad electrolytic caps, but it being a Pioneer, I strongly suspect the black leg transistors.
You sir are correct. 2SC1451''s were the issue.
@@vintageaudioaddict Those and a few others, like 2SC458's keep me busy!
I appreciate it the way you explain things to the common man not somebody that's advanced in electronics. I just have a lower knowledge of electronics so it's very helpful to keep things simple. I would appreciate any other practical video tips.
My problem (and I consider it to be huge) is my Kenwood KR8050, which I bought new has started acting up and I can’t find anyone around here (north Carolina) who will do a complete overhaul with new caps and transistors where needed as well as a cursory cleaning (unit is very clean physically) and do all the proper testing to give it back to me working great. I bought this new back in 1979 and it cost me more than a few meals but I loved the sound and have never looked back. I’m heartbroken that it has started cutting out and just plain stopped working for certain things. I won’t sell it and I will ship it for repair but only if I can believe they will do a good job. I’m thinking of moving to where people can actually do stuff like this.
First of all your Kenwood is a fine receiver and it's great that you have had her all of these years. I have the exact same model as you in my collection. It's tough to find folks anymore who you can trust working on this equipment. As the equipment has got older so have the folks who use to work on it. The technicians are just disappearing. Do a google search and see if there is anyone within a hundred miles or so from you that could help. That way you could just take it and pick it up yourself. Shipping this equipment is expensive and you have to pack it like it's going to the moon to arrive safe. Good luck finding someone.
Thanks for sharing. You have the most amazing collection! Cheers!
Thanks for the kind words and for watching.
Hey Chris this voltage test is performed WITHOUT audio going through the unit?
yes, that's correct. Volume minimum and select aux for the input function.
Where do you place the wires from the multimeter on the amplifier?
I like the time trace. What equipment and software did you use?
Siglent SDM3045X meter and EasyDMM software.
Thank you, This is some valuable information and something I’ll be checking today. Can I share this in one of my videos?
I have a Pyle, the one made from China (2016 era), 4 channel car amp and it was sending many volts (Not sure what it was but knew it was wrong) to the front speakers damaging them. I have not repaired it, but was guessing a shorted capacitor since it looks like this model uses some of them between the output transistors and the the speaker. Now I wonder if one of the output transistors was failing. Still play normal when I tested it but seeing that voltage at the speaker connection is a problem. (Pyle used to be made in USA.)
Yep... a Pyle is a "Pile" for sure no matter the year or place built. Just chuck it.
@@Rob.DB. The Pyle speakers was were I first heard of Pyle. Then in the 1980's,1990's I saw they had some amps at a car stereo show/sale. Yet I recall telling a stereo shop about the Pyle amp and they said that Pyle did not make any amps. The only problem I had with their speakers, was the foam edge would go bad but that was the thing with most speakers of that time era. I did not know until much later, around 1996 that those foam edges could be replaced. I did that to my 12 inch woofers, then some other brand stuff later. Some people frown on the foam edge design, but it has less resistance, less weight, so it is more responsive then the rolled paper or the rubber. I think Quam was the first to come out with the foam edge for speakers. Now Quam stuff was more hype then quality. Nice foam edge but the 6 X 9 speakers were rated for like 5 watts.
Another speaker I think was hype back in the 1990's; was Pyramid. High wattage but stiff as a board.
Is it worth it to change out the old RCAs? To the gold plated one's to get better sound?
I legitimately thought you had passed on. Glad to see new content. Cold solder joint or a flaky transistor.
Just rebuilt an SX-737 and the DC offset was spastic, replacing the "shoot on sight" transistors on the TONE board with some KSA992 and KSC1845 and all is quiet. Pioneer was prescient in knowing what transistors were going to age poorly and used them a lot in this era.
spoiler alert........ It is a certain transistor type(2sc1451). That transistor is a known troublemaker in vintage audio equipment. Still alive and drinking daily. lol. Thanks for watching!
Could this be noisy transistors,
I had that w a KR6600 good sound quality btoken w pops n craclin.2 thumbs up
So glad you are back!!!
Thanks!
Some good info and advice. I have six vintage units, most never touched except offset and blown out occasionally. I suppose after 50 years of bliss there could be an issue. Or ...a few years of crap, then more crap, then more all in search of that 50 year old sound with newer junk....My truck will also need repair down the road.....still I use it....
Happy to see you back...
Thanks for all the work you've done and shared with us.
Your very welcome and thanks!
Behringer KM750 750W 2-channel Power Amplifier and haven't looked back. Miss my Onkyo power amp but it just wasn't worth fixing. I did have to put a 12v Noctua 92mm case fan with a fan temperature controller and small 24v to 12v buck convertor, because the OEM fan was pretty loud and always ran at max speed. But there is a ton of space in the case. The fan now almost always runs at the minimum speed I set and is inaudible, when it does ramp (does it even) the music is so loud I still can't hear it. I am not an audiophile but I think I have a fairly discerning ear. I know it sounds great and much better than a worn out vintage amp.
The biggest thing I do not like about this vintage is they do NOT have banana plugs or 5 way binding post. You are supposed to thread a 14 gauge wire into a little hole.
Yes, that's true. You are limited most of the time to the smaller gauge wire with the older gear. Thanks for watching!
Change out the old connectors to newer ones.
They were designed according to the level of sound performance they offered. Good for the old boys who want to relive their lost youth, & maybe now that they're old & grey they can finally afford that big flashy piece of mass-produced Jap-Crap they lusted over but never were able to buy when their face still had pimples on it & their heads were fully covered with hair...Now all this 🫨🫤😕☹️🫣😱😵💫🥵-sounding 🦨💩🚮 mass-produced AUDIO DEATH is insanely collectable (or at least, insanely priced...🤡👺🤡) as folks first threw all this 🤮 in the tip where it sonically belongs, then stood around whilst rich Vietnamese guys bought up the rest of it to send by the container load for 🤑🤑🤑😎 to the ol' communist Homeland where they resell it for several multiples more than what they paid...And so now all those dime-a-dozen shiny faceplates are getting a bit rare! 🤔🧐
Vinyl FINALLY came back after all the same DUMMIES finally figured that Seedy sucks & that "Home Theatre" was nothing more than "💩y TV sound, only MUCH louder". So once EVERYONE ELSE started playing LP's again, mostly your kids, & all the REALLY good sounding vintage Tube gear had long disappeared (mostly to Asia as well, notably Japan & then Hong Kong) these same Japanese transistor radio connoisseurs found it socially acceptable to be seen playing their own LP collections...if they hadn't thrown all of them away by 1988...
So the old component Hi-Fi set that's been sitting in the garage/attic/cellar unused for the last 30+ years gets dusted off because...why spend money to buy something that'll actually work & sound good the moment you plug it in? Why not risk setting your house & hair on fire & just plug it in & see if you can get the smoke hidden deep inside those old neglected fossils to come out for you?
Are these the same guys who need big speaker wire connectors, too? If you're going to acknowledge that certain things, like wires & cable, are important; then you're admitting that certain things have moved ahead in the last 40+ years of Hi-Fi technology. Like sound quality, for instance.🤔 🤣🤣🤣
Otherwise, this trip isn't about sound quality; not that 98% of these vintage Japanese receiver collectors have developed any hearing acuity in the intervening decades. Otherwise they'd be going into Hi-Fi stores, the few bricks & mortar ones still left anyway, & buying stuff that not only sounds alot better but comes with a factory warranty & won't need a re-capping job until at least 2050. And the way prices are going, you can buy a brand-new Made-In-America-by-Americans top-of-the-line McIntosh or Mark Levinson for less money (and hassle, and grief) than a 45 year-old Marantz 2500 (or 50 year old Fry-An-Ear SA-9900...). This new stuff sounds about 100x better, works about 100x better, all the parts for them are still readily available & don't require a scavenger hunt on ePay for a transistor that was custom made for one model of Soundscrewy in 1976-77 (& will cost you $300, for a used one that's probably as blown up as the one that you're trying to replace, from some guy in Malaysia or Nigeria or Belarus). Oh, and the new stuff has noiseless switching, instead of requiring a steady diet of De-Oxit applied to its NON-REMOTE CONTROLLED front panel function selectors every 3 months or 3 hours of use (whichever one comes first). And best of all, has WELL-SPACED, HIGH-QUALITY RCA jacks & WELL-SPACED 5-way binding posts because the gear was designed & built for them, by people who ACTUALLY LISTENED TO THE DAMNED THING when they were designing it, as opposed to the faceless committee of tin-eared Japanese Engineers with jobs-for-life within their giant Japanese Keiretsu (Sansui & Luxman occasionally excepted) who just designed the unit to have better specs than last year's model & the new models from the giant keiretsu across the street, & the only one that ever actually listened to what they designed WAS YOU! 🤓🤖🙉🙉🙉
@@stillastillsfanChange out the old vintage junk for new McIntosh. And it'll probably cost you less, too.🤨
That’s because fat speaker cables are a joke.
Where can I find a Sansui 9090 I bought one in 75 in Germany while serving in the Army
Maybe eBay? Not going to be cheap from eBay but there is probably one or two for sale.
Great video, Good to see you again. looking forward to the repair. cheers
Thanks 👍
Sounds to me like this issue is either a possible loose connection in that pre-amp/power amp separation switch, which could be remedied with a good contact cleaner and lube, OR, it very well could also be caused by some leaky or even totally bad electrolytic capacitors somewhere in the circuit of this amp... In this one's case, probably somewhere within the pre-amp part of it, since disconnecting the two parts by flipping that switch seems to completely stop the noise...
But I will look forward to seeing and watching your repair video for this amp to see what it actually was and how exactly you fixed this issue!
spoiler alert........ It is a certain transistor type(2sc1451). That transistor is a known troublemaker in vintage audio equipment. Thanks for watching!
Such a noob take...lol....deoxit and caps to the rescue. LoL
@@Poppinwheeeeellllllieeeeez Hey, sometimes it's actually just as simple as that in fixing vintage audio gear! I've totally fixed used gear exactly that way MANY numerous times over the decades... Sometimes it actually IS something more difficult and expensive to replace, like proprietary components or discrete semiconductors, sometimes which are obsolete so they have to be substituted with something equivalent or as similar as possible, then the surrounding circuit be adjusted accordingly if necessary, but you always want to at least TRY the very cheapest and most BASIC things FIRST, BEFORE you automatically assume the absolute worst and just start throwing expensive or hard to find parts at something!... So not exactly a "noob" take on this topic, but thanks for your assuming that, because now that assumption actually just makes YOU seem like a "noob", because any really good tech or repair person should ALWAYS try the most simplest and basic things FIRST, before ever having to get into the replacing of actual semiconductors and such.
You should know that too if you're REALLY into this sort of thing, so not to be mean at all, but just making it clear that my initial thoughts about this problem would still have been a good place to START at least, and THEN, if that basic stuff, (which should be done in ANY case, with a truly Good quality restore of vintage equipment), still didn't fix the issue, THEN you start checking ALL of the other components in the circuit!... After loose connections and bad caps, then semiconductors. The guy in this video probably did exactly that himself, unless maybe he ALREADY knew in advance to check that one specific transistor exclusively and first, maybe from prior experience with this specific amp model before, OR maybe he took a suggestion from an online repair forum or something?... But without knowing ANYTHING about what exactly is wrong with something, you always start with the very simplest, quickest, and easiest things to repair or replace first and foremost, then go from there.
The fact that he said that it actually was a transistor that went bad is just a coincidence in this case, because I've heard noises exactly like what he showed in this video being caused by nothing more than loose connections in switches and/or from bad electrolytic caps in old vintage gear, more oftentimes than not, which is of course a super easy and (usually) cheap thing to fix, depending on what all else may be wrong with the equipment being restored.
Anyway, have a good day, and let's both just look forward to this guy's follow up video to this one, showing exactly what all he had to do to get this beautiful amp working properly again!
Got ‘em!
I recently repaired a (not really vintage because it;'s from the 2000s) Yamaha RX-371V receiver that I had salvaged from Goodwill for about $10. It wasn't powering up, so I found the schematic and started probing. The unit has 2 transformers, a main one that powers the unit when it's on, and a standby transformer that powers the IR receiver and the power button circuitry. The secondary of the standby transformer wasn't outputting any voltage and the secondary was open circuit. I found in my stockpile of parts a suitable replacement (compatible voltage, larger rated power of 16W vs 5W the original, larger footprint too so I had to get a little creative to install it). After replacing that, the unit powers up and works great.
The nagging question that remains in my head is: what could have caused that failure. I probed around the standby circuitry and everything checks out, no shorts, no bad caps etc. And I wonder how long until it fails again, this time maybe taking with it something else inside.
But all in all for a $10 price tag, a spare transformer and a few hours of work, I'd say not bad.
Where did you get the parts ?
Where did you get the parts ?
would you please share with me what you are using the measure the voltage over time? Thanks. Maybe I should ask what is an economical way for me to make these measurements?
So glad to hear from you! Looking forward to future content
Thanks!
I just subscribed.
I'm going to take an educated guess that this was a small signal transistor causing this issue. This is particularly nasty in direct coupled amplifiers where a complete failure of a small signal transistor can cause an output offset almost equal to one of the supply rails.
You are correct. The issue was caused by a known troublemaker transistor in vintage audio gear, 2SC1451's. Thanks for the sub.
@@vintageaudioaddict you're most welovme regarding the sub. Cool channel.
Those Japanese small signal transistors are as notorious as RIFA caps! Did they have the telltale black lead syndrome?
Chris is Back...Finally! Lol
Thanks a lot for checking in. Yes, I 'm still kicking.
I’m not sure that would be correctly considered a DC off set issue. I could be wrong, but I equate an offset issue with a power amp imbalance between the rails. Not a power amp correctly responding to an input signal……which is what you ultimately have.
You could say that. The amplifier section was responding correctly to the signal it was receiving from the preamp section. The DC voltage speaker protection circuit responded correctly when the DC voltage being sent by the amplifier section to the speakers was high enough. Bottom line, everything worked correctly to save the speaker drivers.
Terrific video, I really enjoyed it.
Thank you very much!
So adjusting the DC offfset fixes these spike? Have my Marantz 2226 clicking after a couple of minutes of playing then it stops ? Sounds good though no static or distorted sound?
Even worse is: The "protection" circuit fails.I've seen a Cerwin-Vega 15 inch speaker catch on fire
Sanyo 100w/per amplifier-actually I smelled it first then the speaker tried to leave the cabinet
What is the easiest way to graph the DC over time? What do I need beyond a DMM?
I'm getting to the end now. I'll finish and hopefully will see the answer.
So would a hold function be of use? Could it show the peaks?
You will need a DMM that you can hook up (usually via USB) to a computer and some software that usually comes with the meter. In my case the data you saw was captured by my Siglent SDM3045X and sent to my computer. I then recorded it using video capture software.(flashback express)
So on this unit you’ve isolated the problem to the preamp?
Yes and actually here comes a spoiler alert. The issue was caused by 2SC1451 transistors. Those are known to cause issues like this.
Do you have any recommendations on what electronics books I should study to get up to speed doing what you do? I’m a fan of your channel.
Thanks for watching. I'd checkout some videos. On UA-cam there are a lot of smart folks that are into electronics. Both basic electronic theory as well as others who work on the vintage electronics like myself. Most of it is not that difficult if someone shows you. With video's you can watch how something is done or how it operates.
@@vintageaudioaddict what types of diagnostic tools are necessary to get started?
I do indeed have an inexpensive moldymeter here. I can now repair it all!😂
My guesses on that would be switch cleaner on the PSU connectors in case one of the DC rails is causing the problem, and often you get a preset bias potentiometer to balance the op stage and they can get a bit corroded, so more switch cleaner. Finally I would resolder any PCB joints that might have cracked up due to thermal problems, e.g. WW resistors, OP transistors. If that failed another trick is to use freezer spray on individual components while measuring the offset.
Happy to see this video. I was worried something had happened to you. I enjoy your videos.
Thanks for checking in and watching. All is well. Hopefully the same for you.
@@vintageaudioaddictI am well. I have a modest amount of tools and meters but have brought a SX-727, a 2220 and a Yamaha C-60 back to life in the last few months. I am slowly immersing myself into the hobby. Mostly fixing stuff for others and occasionally for myself.
I had one such symptom, exactly this condition, in an active speaker, after approx half an hour started making huge noise and stops the useful signal. Was quite hard to repair, because of the way how was designed, with several boards (preamp, tone corrector, another preamp..) stacked parallel. Anyway, the defect was in the polypropilene/polyethilene capacitors (typical 1... 220nF) from these preamps, and I think there are more of them with that issue, cause after finding one on oscilloscope i kept getting the noise, a bit rarer, efectivly the symptom persisted so I decid to change them ALL, and after that only, the ampli was good.
where you locaated a need work done on Kenwood
I'm in Florida and thanks for asking but I'm only a hobbyist. I only work on the equipment in my collection.
Usually the power supply caps, right?
Actually is was a known troublemaker transistor. 2SC1451's
I would say re cap outputs clean relay contacts for spkr protect check preamp out caps too
A capacitor on My yamaha R-1000 receiver gave up the smoke while playing yesterday. I racapped it, but a transistor went bad. Waiting on parts to replace the transistors on the power supply board.
Sounds like a good plan. Your Yamaha is a fine receiver. I'm glad that you are fixing her up.
I have the same receiver... haven't used in 18 years. It looks perfect, love to sell it.
@Damone7653 Enjoy that receiver. It has great sound! It was second from top when it was released after the R-2000.
I had to stop the video a couple times where you pan across all that gear to confirm you show the same Luxman cassette deck that I've got. I have a bearing problem with the motor, sometimes it won't spin up.
Luxman made some great audio gear back in the day but like most of the vintage equipment they are in need of some work.
So I did a measurement on a old Kenwood amp I just bought that is all original untouched never recapped and it sits at between 0.6 to 0.8mV is that good asking as I know my way around but not that well
Well, if it's really that low then yes that is great. Just make sure that you are measuring correctly. The correct scale on the meter and make sure that your speaker selector switch is set to the speaker outputs that you are measuring. Thanks for watching!
So was the noise in both channels?
Spoiler Alert......2SC1451 transistors. Known troublemakers in vintage audio equipment.
@@vintageaudioaddict Same issue in my Akai 1722, 2SC458 known to be noisy.
Very informative, thank you for posting this. Looking forward to the repair video
Your welcome and thanks for watching!
@@vintageaudioaddict Can you please let us know what software you are using for this video? Thank you
hey Chris, do you know what is going on with the hifiengine? i used to have an account but had to care for my elderly parents for a while so i was not able to be very active and they killed my account and now they do not allow me to create a new one! i am trying to power up again and have no idea why they killed my account. thanks 🙂
Other's have had that same experience. I've heard that they are disabling accounts that have not logged in for a while. What a while is?, I don't know. Also, they are not taking any new accounts for some reason. Again, I have no idea why.
@@vintageaudioaddict i can't even send them a message! if your account is still active, would you please send them my message and see if you can get some answers? if they need help, i can volunteer. i was a very active member but as i said, my parents came first 🙂
Is the amp set to AUX for these tests?
Yes and the volume control set to minimum.
What is the unit on the thumbnail?
I had a Marantz top tier stereo amp. Very, very heavy. From late 1970s. Sat in storage for decades. Sounded great, except scratchy pots, when I fired it up about 2012. Then one day, it just would not turn on anymore. Threw it out.
I have an old pioneer amp that was sitting in the rain for days before i found it. It works but the solder is corroded and there's DC on the outputs. It even blew one of my tweeters. I know i need to fix it but I'm dreading disassembling it and cleaning every solder connection and replacing each component. For now i just let it run for a long time and let it warm up before i use it. Lol
Great info Thank you
Glad it was helpful!
Good video. It is hard to get people to understand there may be problems below the surface. Working-Good! Not working-Bad! btw what is the stereo in the thumbnail?
Hey man! Great channel u have here! Iused to fix antique radios
Still have a Radiola 60 and its wrkg .
Woul really like to know more bout my Sx850 and 950. And kenwood 6600 as aux input ia a dogs dinner. The 8 and 950 are great rcvrs, kenwood 6030 has lots of beef. Yup ill be watching you .lots of rcvrs have the jumper pins. Have even seen rcvrs being sold with out them.
2SA726 transistor in the differential amplifier was a problem child in many Pioneer and other Japanese preamplifier front ends.
When you don't hear any crackles and pops, its sometimes best to attach a dummy loaded resistor of the correct impedance value and then measure the speaker output across each terminal with the resistor attached, that way you'll be able to see what kind of signal your speakers are receiving.
That's the way i do it, firstly without & then with a resistor.
Hi Chris, and wider audio community.
Not sure if the topic of this video is what I'm experiencing but I have an old Denon PMA-350SE. Quite randomly during usual low volume use it would suddenly jump up to max volume static horrid noises, only way to stop it was to turn it off. Often it would then be fine when turning it back on for a somewhat random amount of time before doing it again, it was fairly inconsistent. I haven't used it for a while now because it was honestly quite shocking/painful when it would bug out like this. Wondering if this is a common issue you might be able to identify from this brief description?
Cheers for any help.
It seems as though we don't need a meter. We can just listen for static when idling.
Yes, you could but keep in mind that "static" can have many different sources unrelated to this amplifiers issue.
@@vintageaudioaddict Thank you for sharing your wisdom.
for abnormal dc offset ,the first thing is, always check variable resistor or trimpot of dc offset setting and bias in vintage amps. and then leaky bjt
I have a Sansui 5050 receiver that went totally silent while listening to music.Checked all the internal fuses, they are all ok. Is there a obvious component failure that would cause dead silence while power is on.Unit lights up ,no sound.
It's tough to say. If it's all the inputs, It could be in the power supply section, protection circuit or the amplifier section that caused the protection circuit to operate. Sorry that I can't diagnose exactly what your issue may be.
I was just working on mine and if you open the unit towards the left is a preamp board? with a pin connector on top with 3 wires I believe. I removed this board and the top pin connector and cleaned the contacts with Deoxit. Reinstalled the board (snaps into place) and the dead channel came back to life.
Do you have a Sansui 5050? Both channels are out.,No sound.There isn't an intermittent problem that would indicate a dirty contact.Unit lights up ,no sound.@@68wrko
@@68wrkothat’s the driver board. The pre amp is in front attached to the pots.
Thanks......it worked reinsertign that board and cleaning the contacts.@@alexw890
So, if I start hearing that static while the amplifier is "idling", does that mean that I have this problem?
Are you familiar with the Realistic STA-117 AM/FM Stereo Receiver circa 1980?
This would be a decoupling capacitor issue, yes?
Spoiler alert. The problem was caused by 2SC1451 transistors. These are known troublemakers in vintage audio equipment.
Anyone knows what that amp in the thumbnail is??
You must recap all vintage stuff these days ... that's if you must use it !!
I agree 10000%
This is the voice of Thom Shane from the Shane Company who used to sell diamonds in Seattle. Somebody out there knows what I'm talking about but I have been trying to remember where I heard your voice before and it's a dead ringer
I think this is most likely due to a flakey dielectric in an electrolytic cap. With old gear, it's always a good idea to replace all the electrolytics. Even a cap that tests OK regarding leakage & ESR, may crap out soon. For tube equipment, it may have those wax-impregnated paper ones, and they should be replaced, too. Then, it's always a good idea to check & adjust the bias currents. The service manual (available for most old gear) will give instructions. Other possible causes of the problem are, dirty switches/pots (clean & lube), cold solder joint (find by tapping with a plastic screwdriver handle, around the PCB, or just resolder them all), and a noisy transistor (locate with "freeze spray"). Of course, you can fire up the 'scope, and track the problem down. So you say you're not an electronics technician? Then become one! There's nothing like an avid interest in a subject to motivate study.
BTW, I'm drinking as I watch this! Cheers, gang!
I'll join you in a few.
cheer for the video chris
Thanks for watching!
IDK. I’m still running (bridged) Carver TFM-45’s mated to Sony TA-E9000ES Processor and my ol’ school Polk 1.2tl SDS-SRAs and Velodyne FSR15s (x2) still image as they did from the day I first purchased everything.
Granted, every 10 yrs I replace the Polk drivers and tweeters, and the Carver’s had new caps, etc. installed 5 yrs ago. I will NEVER part with my gear!!