Pioneer SX-434 Vintage Receiver Restoration
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- Опубліковано 7 вер 2024
- Join me in another vintage audio restoration project. This time I'm laying hands on a Pioneer SX-434 1970s vintage receiver. Recapping, adjusting and modding it for LED lighting in the process.
Here’s the service manual: www.electronic...
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Those metal knobs in old receivers have such satisfying weight, unlike the cheap plastic knobs on today's models.
Yeah, they don't make 'em like that anymore... :/
So there is no need to add thermal grease/compound in between the transistors and the plastic isolators? and if you do use the thermal compound would it help with heat dissipation?Great video, very clear and informative.Cheers
My Dad had this exact receiver, it was a pretty good unit, I grew up with this machine!
I'm in the same boat as you and I took possession of it around 8-9 years ago when my dad passed away at the age of 94.
@@hondaphan4172 ♥
Got my first hifi system in 1974. It consisted of this Pioneer SX-434 receiver, BIC-920 turntable and KLH model 31 speakers all for less than $250. A few years ago at work they were throwing out this receiver. I took it to my fixit guy and for $60 he restored it. Now the Pioneer SX-434 sits in my kitchen and powers a Nakamichi BX-1 cassette deck and Boston Acoustics A-40 speakers. A very happy ending.
Oh, nice that you could recreate the old setup to an extend. As I said in the video, they just don't make this stuff like they used to anymore. :)
@@JanBeta, just been looking at old Pioneer receivers and the SX-434 sells for more than the SX-4, 5 or 6. It is a desirable unit and is a great little receiver. Love that back lit blue dial scale.
Thank you very much for the walkthrough. Just got finished recapping my SX-434. Wouldn't have been able to do it without you. Great tip on cleaning the potentiometers. My balance was always a little crunchy but its perfect now. No need to replace it.
very nice!
i don't know my way around servicing vintage Hi-Fi besides changing caps and check for right voltages, but i like watching stuff getting repaired.
Thank you! I started vintage audio restoration a while before I started this channel. I actually wanted to do a lot more of these but then the computer stuff got in the way. ;)
When you're replacing a single cap with two that don't exactly match the original, it's good practice to write on the board what that should have been (like .47uF), for future reference :)
Oh, that's a good idea. Didn't think of that at all. Will do that next time! :)
instaBlaster
Loving the retro repair really built to last these amps not like the throw away hifi of today with custom ic etc which cost the earth if you can get hold of them to replace. Great Job looking forward to other repairs.
Yeah, they surely don't make 'em like this anymore... ;)
had one of these when I was a kid. hooked my NES up to it and an old composite color monitor. later a betmax for some TV.
fun times
ok I lied it was an SX-636 they all look so damn similar at first glance
Yeah, I think they used the same chassis, too. :)
This is great. About to search for the Marantz rebuild. I just acquired a 2240 that needs love.
My vintage stereo project (were I going to attempt it) would be a couple of 8-track decks. One is a full player plus radio receiver (belt good, no playback) for a friend, and the other is my own 8-track *recorder* that I finally found where I had stashed it away (same problem, belt is good, no playback).I just don't have a good soldering setup (irons *or* place to do it)
13:40 I got the successor of the desoldering station, the ZD-985, but it's basically the same. It's the BEST TOOL EVER - so much better than solder sucker & wick. Thanks for the recommendation!
Oh, cool. I didn't really know how good the new versions are so I'm careful to recommend them. Good to hear they work. :)
I enjoyed watching this. Thanks for sharing with us. I wish I had the knowledge on how to do it.
What a really beautiful receiver! Great job!
The power transformer is wound normally. The copper wrap, that lies over the windings, is to act as a shorted turn outside of the core of the transformer, which reduces the effect of any magnetic field from the transformer, that would induce hum into the nearby electronics.
My first serious audio equipment was a Pioneer SX626 that I received as a gift in 1971. It was a nice little unit, a lot like this. By the mid-80’s, the sound was getting weary so I donated it. Hopefully someone knew how to service it and got more enjoyment from it. If it is still around, I have seen people asking $350-$400 for one.
Loving the LED mod !
Thanks! It was really easy to do on this one as there was a lot of space to add the rectification circuitry. :)
after finishing its a pitty you couldn't show us more of its sound cause of youtube's music detection algorithm
Thanks for the good video.Regarding changing 6 bulbs on the radio.
One thing you should have done is adding thermal paste between the mica and the heat sink, and between the mica and the transistor. Rest of the work was really good 👍👍
Great video Jan. I didn't know you're also into vintage audio receivers. I enjoy your Commodore 64 videos but seeing this is also very cool. I'll check out your Marantz and Sansui resto videos. Danke!
Thanks Luis! I actually did old audio gear before I did old computers. The channel was initially intended to be more about audio repairs but in the meantime it has a life of its own. ;)
I like the part where you convert the bulbs to LED's. Wish you spent a few minutes going over why you added the capacitor between the rectifier.
i replaced the light bulb on my saba RS 910 with a LED as well (because i had 2 bulbs die in under 3 months already) - good thing the saba has DC for the bulb so all i did was add a resistor before the LED and some mechanical modifications (LED diameter was larger than the bulb so i had to make the hole bigger)
Yeah, these bulbs can die pretty quickly. It seems they especially die if you handle them while they are hot (I guess that's what happened in this case)...
I would replace small caps (1uF and less) with film capacitors. You can get them in small sizes and they last forever.
Great video. I have the same one, the right channel has 24mv and the left 0mv and it sounds distorted, how can I adjust the bias so that it sounds good
I have one and the nob to turn it on is super stiff how do I make it not super stiff. And this one of mine has the original capacitors and they work fine every thing works on it. And the balance nob and volume make a scratching nose. How do I clean them because it sat in a room where I put my hand on the top and the dust made my hand go brown.
Excellent work Jan. I enjoy this type of content very much.
Thanks George! Glad you liked the little restoration. :)
All we see is Jan BETA Jan BETA, when are we going to see the Jan STABLE version 1.0?
The BETA version is MUCH improved over the ALPHA version.
At least it's not a nightly build :)
But don't you love the channel? I do the same stuff in my home workshop and i can understand Jan is a very good engineer
I do love this channel. I'm learning quite a bit watching Jan.
Stable versions are so boring, tho.
Great Video! Thank You for the detailed information and innovations! THIS WAS VERY HELPFUL!
Oh, glad I could help! That's what these videos are for. :)
Very informative and fun to watch!
Nicely done Sir, 10/10 would watch again \m/ :)
Thanks Jay! :)
Amazing video like always. Thanks a lot.
Thanks Fernando! Glad you like it. :)
@Jan Beta... just a tip..... as you see at minute 39:01 ... the numbers 94.. 104 and 108 of the dial... are illuminated with a much clear tone of blue.... because it hits directly the brightness of the LEDs on those numbers ..... I got better result in my amplifier.. pointing the LEDs to the back.... pointing to the silver plate behind.... so the numbers get illuminate with the light that bounces on that silver plate more smoothly...
Yes, that makes sense. Thanks for the tip. I was experimenting with putting tape over the lamps as well with some good results. You definitely need to diffuse the light more as the LEDs are much too directional.
The transformer isnt "flat wound" but the copper strap you see around it is quite common on EI transformers used to power audio circuitry. It is simply a screening band to keep emissions down.
The main bugger with these amps (and many Pioneer made) is that they use an odd "multiple diode" device as part of the bias current feedback. If the output transistors fail, these diode strings frequently get toasted, and it is impossible to get them... so you either have to make a hack with several 1N4148/zener diodes, or create a VBE multiplier using a BD139 or something like it.
It's a nice little receiver you've got here though.. i'll carry on watching now (I got 5 minutes in before commenting ;))
For the 0.47uF electrolyic.. next time.. feel free to use a 100v NPO/COG type ceramic capacitor :)
(edit: Im going to get to be a real pain in the ass arent i ;))
edit 2: looking at where those 0.47uF capacitors are used, they are used as audio signal coupling. Fitting 1uF capacitors should be just fine. The implication of doing this is that it lowers the -3dB cutoff point of the high pass filter that is formed in the typical use of these capacitors.. but it wont cause any major issues (and give you moar bass! :)
20:15 - these insulators are called Mica washers. They are primarily as you say, to insulate the heatsink electrically from the tabs of the transistors which are connected to the Collector pin, and thus typically have the rail voltage on them.
Im not sure why Pioneer didnt do this originally, but there should be thermal paste between the heatsink and washer, and then between the washer and the transistor tab. Very messy.. which is why many modern things now use the grey "rubbery" washers you see which are both electrically insulating, and thermally conductive. I suspect at just 15 watts per channel, it didnt matter much..
26:02 - im glad you've heard about the criticality of tuner alignment. I have seen plenty of tweakers on DIYAudio completely ruin their tuners by doing a shotgun recapping of everything - including the ceramic caps and things like polystyrene film caps. You are absolutely fine to replace electrolytics though - they will only be used in supply decoupling and audio coupling places, rather than in tuned oscillator places.
Likewise if you see any little wire wound coils that look as if they've been squished or prised apart and sealed with wax, dont EVER be tempted to "neaten" them by straightening ;) It is quite common to adjust an oscillator used in tuners by moving the windings on the coil and then setting them with wax. Of course this is done while frequency measurements are being taken at points in the circuit, to ensure everything is working as it should.
30:25 - hmm, what an odd way of adjusting the DC offset and idle bias current. For the bias current, they are basically either shorting out a 10 ohm resistor, or not. I suppose this is better than having a little 10 ohm trimmerpot in there which would go nasty with age... especially with those fragile STV3H bias diodes !
The DC offset will have changed simply because of changing the capacitors C35-C38 , those 0.47uF capacitors you came across. As long as youre not seeing more than +/- 100mV on the speaker terminals under load, I wouldnt worry. Sometimes the output DC can rise higher than this with age, and occasionally it's due to the transistors in the input stage (Q10-Q13) having drifted with age.
between TP1 / point 27 and between TP2 / point 29 is an indication of the idle bias current. For your 8.8mV reading it is calculatable by ohms law using the value of the emitter resistors (0.5 ohms). So that would mean 16mA. Sounds reasonable given that they are TO-220 transistors.
BTW im sure you know some of this.. but it's good reading for your followers who may not ;)
New subscriber. Love your videos. I have a sx-650 pioneer. Changed the display bulbs to led was fine for about six months now they flash. Help.
Great video, one question pls. Where i can buy that sanyo a5870 transistors?
Bom dia amigo ,tenho um sx424 como é possível adquirir 2 botões de ajuste porque aqui não encontro..obrigado
Nice video. Thank you. I have the same receiver, bought used last week. It's in almost mint conditions. When I listen to the radio and the station is in stereo the red light appears and shows "stereo". However, if I push the button "mono" on the receiver, the light does not change. The sound does change but not the indicator light. Is that normal for this receiver? (With my Realistic gear, when I do that the stereo indicator light goes off.)
I don't have the receiver anymore to double check but if I remember correctly that is normal behavior. The Stereo indicator just shows you that the picked up signal is stereo, it is not affected by switching the output to mono.
@@JanBeta Thank you.
I had the same, but now there's a lot of humming on the AUX and TAPE IN inputs. Do you know what might be wrong and how to fix it?
Look for bad filter capacitors in those input paths and also check for bad ground connections (broken solder joints, ripped wires, loose screws on the metal chassis). If the other input sources don't produce hum, the fault should be located close to the humming inputs.
@@JanBeta Thanks for your advice. Appreciate it.
Would you mind telling me roughly how much a restoration like that would cost, I just bought a Pioneer sx-770, would like to get it restored.
Master, how many volts for 6 lamps for the radio?
Hi, I bought one of this a week ago, exactly same model, it was working fine only minus was only half of the front radio quadrant was lighted, and the bass knob was making a static noise but just when increasing and decreasing the bass. I removed the knob and sprayed some electrical contact cleaner inside of it, and the result was lost of bass and and almost all the sound, now only little sound is coming out from all outputs. what can I do? please give me some advice, I will really appreciate it. ☺
10:51 can you believe the construction of that audio unit........ I mean.. have more solid metal than many modern cars... :-D
@ramdileo take a look to this one.. ..
Yes! And it is pretty much the bottom of the line model!
I always replace incandescent lightbulbs with regular automotive LED’s and never had a problem. With out the rectification circuit. Can you explain. Please
Great video! I used this to change the lamps on my Pioneer SX-434 and worked great.
Still the sound is failing from time to time (specially after 5/10 minutes of usage )either on left or right channel. I ear a sound like an explosion really loud or just fades and becomes intermittent...
I already cleaned it and used the Teslanol contact spray
Could it be the capacitors? Any ideas?
Thank you!
Bravo extra !
Oh, thanks! :)
The Pioneer SX-434 was made from 1974 to 1976 - Yeah I cheated and Googled it.
Ha! :)
I have a similar one but one channel has a scratchy sound output. Shop says not worth repairing. Can you help?
Are you serious? They actually told you that? My advice would be to find another shop, if possible.
@@hondaphan4172 Found another electrical shop locally. Called them and they asked me to bring it. I told them everything works and just the right channel was not working properly. Then after three weeks I called and they told me not worth repairing. Guess what when l got it back.. receiver no longer works 😤 l wish I did not take it there.
Hi from Spain.
Do you know how to say in English to the welding or joining of spiral cables? And what tool is it made with?
Thanks and best regards.
You probably mean a wire wrapping tool. :)
@@JanBeta OMG. In Spain it´s called "grapinadora" or also colloquially as "chipi chopo" LOL.
They are usually used for telephone networks.
You have helped me a lot.
Thank you so much. Regards.
Excellent project. Can I ask where you got the very small wire stripper you used for the bulbs?
I am looking for the best place to buy the cord that is used for the tunning of a SX727 I live in Qld Aust
I'd recommend searching eBay for "dial cord" / "dial string". I found a vintage hifi seller here in Germany that had plenty of different gauges of the string (used it to restring a Marantz in an earlier video) but you probably will find something locally as well. :)
Never heard of QLD in Austria, must be one of those little villages at the edge of town?
What termination style does the filter caps have?
where fm and am antenas must be conected?
Here is a link to the Service Manual. It is a free site, but you must register before downloading.
www.hifiengine.com/hfe_downloads/index.php?pioneer/pioneer_sx-434_service.pdf
Yes! That's where I got mine from. Brilliant site. :)
Hallo. Ich habe einen Pioneer SX-636 und möchte auch gerne die Kondensatoren tauschen. Habe leider noch nicht ganz so viel Erfahrung damit. Gibt es zusätzliche Tipps, wo welche Kondensatoren geändert werden müssen / sollten? In einschlägigen Foren wird ja oft davon abgeraten, wenn das System an sich funktioniert. Und wo bekomme ich das Material her?
Wurden jetzt Kondensatoren mit höhrerer Temperatur- und Spannungsfestigkeit verbaut?
Und: alles Elkos oder auch Papierkondensatoren o.Ä.?
Wie ist das mit den großen Netzfiltern? Bin etwas besorgt, dass die irgendwann mal hochgehen und ich an einem Herzinfarkt sterbe. :'D
Und wie sieht es aus mit den Transistoren? Auch tauschen oder lassen?
Desweiteren bin ich besorgt um den Trafo. Dieser ist auf 220V~ ausgelegt und kann bei meinem Modell auch nicht verstellt werden. Kann ich mein Gerät trotzdem gefahrlos verwenden, obwohl die Netzspannung heutzutage höher ist?
Ich weiß, viele Fragen. Aber ich freue mich trotzdem auf eine (kurze) Antwort.
Bin durch meinen Pioneer auf dieses Video gestoßen und schaue mir gerne noch andere Videos auf dem Kanal an. :)
Jan I was wondering don't the amplification FETs not need replacing after 40 years of hard labour ?
Oh, of course they can go bad, too. Most of the times they last a long time though and only get damaged if something else in the circuit feeding them goes bad (often caps or adjustment pots)...
OK
i think your yellow led is so dim, because you actually forgot you rectified your nine volts down to five volts, so you need a ~150 ohms resistor instead.
Yes, you're absolutely right. I actually changed the resistor to a smaller one after finishing the video. Shame on me.
is there not a worry that the replacement caps wont last anywhere near as long? after all they are working, they may work another 40 years! many old caps are larger as they dont rely so much on the electrolyte, and it boils out less anyway, there in fact used to be dry caps which seem to last forever, but too large to fit in modern devices
That's a point that's discussed a lot. I tend to replace caps that old anyway and use good brand ones (in this case mostly Panasonic FC) as replacements. I measured some of the caps in this unit and most of them were still good (with slightly high ESR) but some of the smaller ones were off. The whole unit sounds a lot better with the new caps. I find that these old devices sound better after recapping in most cases so I think it's a good thing to do. Even if the caps won't last as long as the originals, they will probably do for at least some additional decades.
well that DOES change my mind somewhat! thanks, i guess old caps are often why old amps sound kinda dull?
Yes, particularly when it's signal coupling capacitors that go bad. The rising ESR and lower capacitance value usually increases the low frequency -3dB rolloff point, so you lose bass response
Wieder ein tolles Video. Für 99% ist so ein Receiver Schrott und wird irgendwann weggeworfen. Manchmal überlege ich solch einen Stereoreceiver mit zwei alten Boxen für meinen Computer zu verwenden, da man heutzutage keine vernünftigen Boxen mit ausgeglichenen Klang (Hoch/Mittel/Tief) zubekommen scheint. Aber da bekomme ich wohl Probleme mit der Abschirmung von Receiver und Boxen...
Vielen Dank! Ja, ich habe traurigerweise auch schon schöne Receiver auf dem Sperrmüll gefunden (oder auch gut, dass ich sie gefunden habe). :(
Am Computer habe ich eine Weile einen kleinen Dual Verstärker betrieben. Das funktionierte sehr gut und ohne Ärger mit der Abschirmung (ansonsten hilft häufig schon ein bisschen Alufolie, die geerdet ist, als zusätzliche Abschirmung). Es gibt einige ganz okay klingende Abhörboxen für Computer, die für Multimedia/Audio als (semi)professionelle Monitore gedacht sind. Kosten leider auch gleich ein bisschen was, also ist die Receiver-Variante eine gute Alternative.
I have a funny feeling that it was probably possible to unscrew the heat sink from the frame and leave the transistors attached.
Yes, it’s possible (I actually tried and edited it out) but the PCB would not slide out because the other PCBs were in the way. Would neeed more disassembly to get it out that way so I went for the transistors.
I guess these ,47µF caps are not THAT exotic... From somewhere I got a whole bunch (100+) of them, never used them and found them always being in the way in my parts bin - i would donate them if you gave me any contact data via PM ;-) (just contacted you on Twitter)
Oh, I know they are pretty common. I just didn't have them in stock so I had to improvise a bit. I'll DM you back later! :)
Since I've been watching a lot of Mr Carlson's Lab (ua-cam.com/users/MrCarlsonsLab) I'm a little disappointed you didn't recap and retune the radio.
I love Mr Carlson's Lab... I just don't have the proper equipment to retune the radio part so I tend to leave the boards untouched if they work okay. Sorry to disappoint in that respect!
To be fair, it looks super difficult and time consuming. He also talks a lot about people leaving radios in worse states than they began.
I realized this might sound a little harsh.
" these things were made to be serviced"....... NOT !!!!!...... anything put together can come apart....that does not mean you should....unless you know what the heck you're doing....which this guy does....but again you can always say you did all of this so you can B.S. yourself through some " audiophile " chat room...