REPAIRING A SMALL TUBE AMP
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- Опубліковано 13 лип 2020
- This session we get an old 70's era tube amplifier working. This was at the time a general purpose amp used for phono, radio, tape recorder, amplification to a speaker. This one is not working and has not only electronic problems but someone has hacked the circuitry getting things all screwed up!
- Наука та технологія
Not only is this guy an absolute genius, but he's also one of the most entertaining personalities on the web! We have more than 150 channels available on our cable TV, but I'd rather watch this guy any day. Thanks, Ron !!
Your right never seen a Glassinger who makes his own tubes.
Logic would dictate Glasslinger to be categorized as a national treasure.
6:47 Who needs Netflix when Ron is in full flow! Great stuff, thanks so much for taking the time to make these videos
Great to see you back again! These videos are pure excellence, and you are greatly appreciated!!!
I like it when you are in teacher mode in your videos. But its always nice to have new videos from you. Its going to with Ron. Thanks for sharing your knowledge with us.
Am always happy when I see you have released a new Video ,Thanks Ron I truly appreciate your time and skill you teach and show the world these fantastic vintage radios.
The instruction and knowledge you share in your videos is golden, thank you for so many ah ha! moments, you are a wonderful source of inspiration and entertainment for us aspiring repair techs
Thank you again & again you have no idea how much we enjoy your videos and your Beautiful ways to approach toward the problems. 73 My Friend Malek KI7DYM
Hahaha, man! I´ve never enjoyed so much a tube repair video like this one! Your laugh and your sense of teaching is awesome. Thanks and cheers from Argentina!
You’re a genius. I’m an EE myself, and you are a master of many trades. Glad your video showed up in my feed, and subscribed. Keep the videos coming.
Ron, you are the everything-teacher I never knew I always wished I had.
Good advices on soldering old stuff at 19:30 ! Not wasting time with wrapping wire before soldering, a small wire hook is sufficient! Please continue your practical video collection. I admire your deep experience and insight in glasstechnology , electron devices and restoring old gear. Thank you!
Stuck in quarantine, this site is a lifesaver.
How many skills can one become expert in?
I know that Grommes Little Jewel 10 watt amplifier personally. It was assembled in 1950 by my 14-year-old brother. It worked very nicely for a number of years. I have no idea who did the "hack" but I'm very sure that it was not done by my brother who was a fanatical perfectionist. Thanks so much for bringing it back to life, harmonics and all!
In electronics, it's called a "mod", not a hack.
Wow cool John what a small world to find the amp your bro built being resurrected on yt!
Hey, Ron. I just found your videos and an enjoying them. I worked in a TV repair shop (remember them?) during college. I restore radios as a hobby for the last 30 years. We're a dying breed... And brake cleaner is a new one to me
Thanks for the tutorial on the spectrum analyzer, Ron. Loved the comment on replacing 80 capacitors in a tv set quickly to make a living.
Thanks Ron for another great video! Please keep them coming, particularly the glass blowing videos!
Love your cycle controlled electronic fuse box!!!
Cup of cherries this time.
Your spectrum analyzer was indicting an overload when you saw the high distortion. There is a high probability that was the cause of your high distortion readings.
Hello young man. I have really enjoyed this video. I think you and I are pretty close in age. I have not had a lot of experience in audio equipment. My field has been in rf but our old principles are the same. These new techs have really missed out on using the old test gear. I loved watching you use that old equipment that some you probably built yourself. Glad to see you put in the notice about using break clean and getting it on the plastic dials. I learned this the hard way onsome old transmitters that parts are hard to find. Keep it up as long as you can. As I aged my hands shake uncontrollably and I have retired. I miss it so bad. God Bless you.
I converted almost the exact same amp to a guitar amp on my channel. As a guitarist, we love the distortion. This little amp makes a great guitar amp. That's likely why the RIAA circuitry was ripped out of yours originally.
Aha Brad I thought it might sound pretty good as a guitar amp!
Always interesting to see your approach and methods. Nice work as usual.
That was a fun video, Ron, especially when you managed to pop that speaker..he-he. That event was water off a duck's back to you...just pop in to the attic and find another speaker, "No problem"...The rest of us here watching would have cursed this event and slung that speaker across the lab in annoyance and frustration, but not you, Ron, he-he.
The cursing and throwing I edited out of the video! :)
@@glasslinger I couldn't possibly believe that, Ron..he-he.
I find pre PCB electronics absolutely fascinating. Keep the videos coming Ron.
Your electronic wizardry is astonishing to watch.
Brilliant Work Earthling Bless Up
very interesting, especially the distortion measurement part...
Good Job, as always.
I searched for years for a Triplett 630 Anyways, finally got my used meter in the mail the other day. Everything Works ! I am thrilled..was going to go for a Simpson 260, but glasslinger changed my mind.
With 6v6gt tubes that's about a 10-15 watt amplifier. Probably between class A and full AB1, so maybe 50% efficiency, 30 watts. Add 20 watts for filaments, that's 50 watts total. Transfromers should be at least 90% efficient, so a 50 watt transformer should lose about 5 watts. I'd say that 5 watts in the transformer is OK, but at the high end of what I'd expect.
As Shango66 has often demonstrated, you CAN often 'repair' noisy pots by cleaning them with de-oxide. Always good to try anyway, as it's easier to clean them than replace them.
Linear pots are easier to diagnose with a meter than log pots. Also many digital meters have an 'analog' bar graph for this purpose! At least my fluke does.
The reduction in size of modern capacitors reminds me of a scene from the movie 'This Island Earth'.
Put the ohmeter on the voice coil!!
Ha! Half of the electronics I see nowadays reminds me of that movie. Plus an interociter seems kind of easy after working on stereo equipment from the '80s.
Why I am watching this? Why this was recommend to me? I don't even know what this guy is doing on this video
10/10 keep going man, you doing great
If you don't understand electronics I can imagine. Cheers there is a lot of other videos that you gona like.
Just found your channel.. I love old electronics and am getting back into this stuff.
blown away by the depth of your knowledge
I like watching someone with experience and a Weller Gun. Nice job.
About the only time I break out my soldering gun is when I need to make a ground connection to the chassis, otherwise I use a temp-controlled iron.
Very good video. This remembers me of my old amp. Many years ago I have bought an used tube amp, it was 100W, and made really clean sound. But I have never take a real look on the solderings. I should have done that because it blows up the output transformer as a bad soldering give up after some time and full current goes through (pentode..) and even worse, someone before me had increased the fuse amp ratings... So bad! So my advice, take a look at all solderings carefully before switch on any amp.
This is a very good video, the suspense never ends! Very educational and enjoyable. You are awesome. By the way I'm only 3/4 through it. It must be hard repairing a kit that was made wrong from the beginning
I had one of these Grommes amps, and a Pilot tuner, sitting atop the fridge in a house I had rented with a group of friends. Sounded good on FM through a Lafayette speaker, and occasionally we'd play guitar through it (lots of distortion). This was back in the late 70s.....
Interesting as always. I was wondering if you could try building a magic eye tube sometime.
Wow that would be just fantastic ! I recently watched his miniature vacuum tube triode video once again & boy I love it ! If he could make a video like that making a magic eye tube sumhow in HD with his new camera, that’ll be just fantabulous ! :D He’s a master of all trades haha :D
Me too. Great idea!
Or at least try to bring back to life a faded one!!
That'd be great. Maybe playin' with different phosphor colors!!
That would be cool! She should do that.
I remember Quietrol. That stuff was (allegedly) mainly carbon tetrachloride (early dry-cleaning solvent) with a dash of light oil, dye (it was red, like cranberry juice) and maybe a fragrance, too. Sure worked a treat.
I still have some Quie-trol! Doesn't smell like Carbon Tet (got a bottle of that too), though any original solvent may have evaporated.
Nice work Ron. Another good vid.
Just found your channel, love these videos! Keep them coming :D
"Had another one at the attic" ha, that was a masterpiece! To think that it was the speaker that was causing problems...
I really enjoyed this restoration. Truth be told, the status quo ante stroke me as really modern and far from original. As if someone's been there, maybe even in this century.
Love the video. Much appreciated. Why do I imagine that the attic looks like the government warehouse in the Indiana Jones movies?
Garage...
Bill Gates.
Wow, now that's a pro tip - using CRC Brake Cleaner for the POTS. Personally I have found some so called cleaners leave the POTS all full of goo and sticky. Potentially makes them worse. Thanks for the tip.
Dunno why the equ got removed, but it was damn funny.
Awesome troubleshooting, thank you for sharing.
Stay safe, much love. ❤️❤️❤️
love your videos keep them coming
4:01
I like how the leak detector has an analog meter, LED read out, and an LCD read out . :)
Love this video, thanks for sharing 🙂👍
Hi Ron, love your channel.
what a treat, thanks for the video
This channel is amazing!!!!!
Glad to see you. Great video. Hi to Miss Kitty 🙂
I love that laugh. "Four capacitors? Hahahahaha, I remember that TV, there were like eighty." Amen to that.
Well done there ,yes was wondering where kitty was ,must be ur summer time there ,over here in new zealand its winter with frosty mornings .Enjoyed many thanks.
Howdy, glasslinger. fairly impressive video. thanks. :)
OH GOD thats something I always wanted to see done by you :D
great video as always
I have never known a capacitor to be "reformed", throw the fucker out and dont be lazy haha
Thank you for what you do.
Just before the amp started motorboating, you used your clothes to clean out the tube holder. I know that's totally unrelated , but I think you're so awesome. I paused video and I can't wait to see what's coming next. I think you're great!
If you remember the old "No Noise" spray, used to quiet noisy volume controls, a few years ago, in a bind, I tried some WD-40. It worked beautifully.
Thanks, Ron!
Tetrachloroethylene is the brake cleaner / dry cleaning fluid. from wiki: "Chlorinated brake cleaner containing tetrachloroethylene will on exposure to high temperatures (above 500 °F (260 °C)) or strong UV light decompose into phosgene and hydrogen chloride, both of which are dangerous when inhaled." so no spray on hot metal!!!
I thought it looked like a 10 watt output amp. We had two of these at our Motel. One for PA address and one hooked to an FM tuner.
Great video
Hi Ron love your channel. I'm a new subscriber. Can I please request that you list the model of the gear you are restoring. I had to take a freeze the video on this one and it seems to be a Grommes LJ-3 Tube Amp. The last TV restoration you never even mention the model. Some of us like to follow along with the schematics which helps learning. Much appreciated. Hello from Australia.
Top show!.
You are AMAZING! I love it Thank you so much for this fantastic channel.👍
Would be interesting to see the curve shape (oscillogram, time domain) of the output voltage. Does the distortion come from the change-over of the push/pull output stage, or does it come in at the peaks of the voltage (maybe sagging power supply?), or does it come from the phase inverter, or....
I love your videos, Ron, keep them coming!
She's overdriving the spectrum analyzer.........look @ 45:14............display sez overload.
You are over driving the spectrum analyser.....
Junior Ocicat your right. Modulation products.
These videos make my day! As a gay Aussie guy I just love them and what's wrong with valve amps? My Primaluna Dialogue Premium HP Integrated Amplifier running EL34 output valves sound excellent so there! LOL
Hey Ron, good afternoon, i was wondering about the turbomolecular pump driver you made afew years back could you please share the schematics if possible? Thank you for the great work
I have always used some type of cleaner-lubricant. Back in the day was tv tuner cleaner. Recent years I have used a couple varieties of Caig De-Oxit. Any reason or advantage using CRC Brake parts cleaner? No residue? Grease-cleaning capability? Cost?
The reason for using it is that it evaporates fast and leave no residue.
Never use anything with lubricants on any contact surfaces. The lubricant will gather dust and just make it worse.
The best is always mechanical cleaning, and the second best is chemical cleaning that leaves a clean and dry surface.
Crc is way cheaper and works just as good. Evaporated quicker too.
Ron on the road again 👍👍
The scope is displaying "Overload" when you increase the signal.
Maybe that is why the harmonic levels indicated are so high.
Try to adjust the scope so the signal does not go overscale in scope mode.
I think I saw a TM506 go by next to your current limiting device. It would be interesting to see a video about that. I also think I saw a custom plug in. Are you sitting on some treasure there?
Quite a lot of even harmonics for a push-pull amplifier. Is there something else wrong, maybe the phase inverter?
love tube amp videos
Fascinating. When watching a sine wave on an oscilloscope (and not a spectrum analyser), at what percentage distortion does it start to become *just* visible? Thanks.
Depends on the type of distortion. Crossover distortion 2% or so, harmonic distortion around 5%. A scope wave form is not ideal to determine distortion other than really bad levels. A half percent is clearly detectable in listening but invisible on a scope.
@@glasslinger Thank you. It's also easier of course to hear distortion at lower frequencies as the harmonics are more likely to be in the middle of the audible hearing range.
Any advice on what test equipment to buy for someone starting out? I would like to repair and build vintage guitar tube amps that I can not afford.
You would do good to get a Triplet 630 VOM and restore it to perfect. The old meter type VOMs are best. You can also have one of the digital ones but they are not as useful. An audio signal generator would be useful. Stick with name brand stuff, industrial quality rather than consumer crap. (hewlett packard) The meter and generator will get you started. Later you could get a low cost scope, but get going first.
I love how you end your videos "okay, that's it." *click*
Ron, did you check the biasing of the push pull end stage? A good symmetric AB stage should not have this much distortion since the signal rides on an almost quadratic function. Also did you check for symmetry on the driver /phase inverter stage?
If i could have chosen an elmer, this would be the one.
Good work
You would not have blown the speaker if Supervisor Kitty was there to keep you right😺
Had a pa .amp had 4. 6l6 did that the paper speaker cone caught fire when I was a kid .🤗
Nice! Do a video with that Gow-Mac Gas Chromatograph. I want to see that.
Hi, at 43:48 and also several times later the analyzer displays OVERLOAD at the lower right corner. The spectrum does not change much when the voltage increases above that level. I expect the analyzer input is saturated and the spectrum shown is incorrect.
Yes! (blunder) I was in a hurry to get the video finished and wasn't paying good attention. Anyway, the distortion was near 10% before the analyzer saturated.
Ron I built your electronic circuit breaker, and it is working perfectly! Are you willing to share any insight on the current limited high voltage supply that you built into the Tektronix Rack?
For info, it looks like Ron is using a HP 3582A 0-25kHz Audio Spectrum Analyzer.
Unfortunately, the power supply uses a surplus high voltage inverter that is not available, so any info would be useless.
that thing would make a good unique door stop though....although i do like a little distortion when i clip my amps lol
That's from the 70s? Looks more like 50s from the components, especially that function switch. (Which looks like it is from the 30s -40s but could still be found later.)
16:45 At least in older equipment, resistors can drift in value quite a bit. I pulled several out of an old Heathkit condenser tester that were over half again as much as what their bands said they were. Gotta test them all.
Ron - forgive me if I'm wrong, but when you are doing the 1kHz distortion test, you increased the output level from the amp but you didn't drop the input sensitivity from 10dB/div so the 1kHz will be way off scale.
It's a log scale so it still fit fine on the screen. This was a quick rough test so I was not carefully setting everything perfect. Nobody would ever use an amp like this for any serious audio reproduction!
Someone’s probably already commented on this, but putting a square wave through a speaker is almost a sure way to blow it out even at low power. That ramp up on the start of the square wave draws a huge amount of current. By the way, this was one of the most entertaining videos I’ve seen in a long time! Good job!
Also turning up the volume on the amp and then slamming your fingers across the guitar strings! The inductance of the speaker will block the sqaure wave harmonics. If your speaker blew out due to "square waves" you simply got a junk speaker!
glasslinger Excellent point! Thanks.
@@glasslinger Yes, I have a MOOG analog synthesizer and blast square waves through my speakers all the time.
@@TestTubeBabySpy You got a Moog? Awesome! Hopefully you have heard "Switched on Bach" by Wendy Carlos? What an amazing piece of work - on a Moog synth!
@@nevillegoddard4966 Yes I am familiar with some of her music.
Is your electronic fuse homemade? Can you post a schematic? or if it is manufactured can you provide make and model? I could really use one of those.
Ron's building video is already on the channel, titled "BUILD AN ELECTRONIC CIRCUIT BREAKER." ua-cam.com/video/SkCMgGuQhYU/v-deo.html
What is the output impedance of the amp?
Hi Ron, could you help me please, which was the video where you declared work had come to a standstill, because the catscan supervisor had settled down on the bench. Sorry, but I love those little incidents, as well as the amazing content. Cheers and stay safe, Mike.
Haha, found it, ' Restoring a 1930's Zenith Table Radio ' at 21:50.
Lol catscan supervisor! Love your pussycat Ron! Give him a pat & a headscratch for me will ya? What's his name?
I recon they removed the RIAA because they wanted to play the guitar over it - and that's what killed the "HiFi" speaker , too. Was there :-)
Although it's unusual that the sub died - but you can kill ANY big Hifi-box with a guitar. At least the tweeters will blow up...
In normal (music) signals there will only be little energy in the hights (about 10..15%). The guitar gives them a 100% ...
Having resurected 50 year old stuff for the last 50 years I've only had to replace nor more than 10-20% of them. What you need to determine is if a capacitor is close to the end of its life. Reforming a worn out capacitor is a waste of time and effort. Reforming a capacitor that has lots of life left SAVES time and effort. What to know is if a capacitor is good and will reform and provide many more hours of service. That determination is made by combining a condition test with reforming. NEVER assume a capacitor is good for any reason. A bad cap is a bad cap as a good one is a good one. If the capacitor reforms according to the current change versus time and applied voltage for a good capacitor, it's a good capacitor and can be left in the circuit. Why safe any capacitor? Because the in most cases the originals are no longer available and the time and effort to make a proper job of replacing with alternate types can be the undoing of a decent piece of equipment. But in retrospect, it's all throw away junk anyway.
Where did you get that printout of the schematic?
Good one, Ron. Any possibility the output tubes are mismatched? Bell always made top notch audio amps. Tell the cat to stay cool!