Servicing a Vintage Pioneer SX-838 Receiver

Some principals of servicing can be transferred to a 939 or sx-1010. However, this shows the primary weakness of the series: push-button switches. Ultimately the cure is to hit them with deoxit D-5, then S5 (shield)

[@bdouglashughes]

I have a SX 838, bought it in 74 and just love it. Loved your maintenance video on this model , very helpful. Thanks JP!

[@deankq4adj125]

Thank you for sharing, loved listening to your thought process and talking as you worked on the machine. Very helpful to me.!!

[@slapjacksoniii7989]

Just bought an Adcom GFA-555 repaired and serviced by you last June (picking up sometime this week). Watching how thorough you were here inspires loads of confidence the unit should work great for another 20 years or more. Have a good one.

[@mdzacharias]

Really good job. I've been doing the same work for 35 years and I can see you have a lot of experience on this type of thing. Those switches are nasty all right but at least you can get to them!

[@SideshowGlazz]

Thanks for the walkthrough. I was leary of ripping apart my SX 828 to clean the pots, but your breakdown helped a lot even though they're a little different. Anytime I need to do some repairs I'll be back to watch this.

[@danbower81]

Nicely done, love the O-Scope.. clearly a functional item in your troubleshooting arsenal. Cheers.

[@christophwjones]

Wanted to say tremendous thanks Jordan! I watched your video on this repair repeatedly then bravely serviced my own pioneer set. You are the man, thank you good sir

[@JordanPier]

+Howler Films (Christoph Jones) glad it was helpful to you

[@God-has-entered-into-my-body]

these are absolutely beautiful sounding receivers. I had 2 of the 538s

[@bg45420]

Thanks for posting this. I have one that I picked up at a garage sale for 25 bucks including a set of boss 201 bookshelf speakers (it was a coworkers sale and I was given a buddy discount ). The unit is near mint and sounds great but, as you stated, those pushbuttons are scratchy. Thanks to your video, I'm cleaning them now. I hope I can get by without removing the toggles and pots. That didn't look like a good time! Thanks again. Also, I subbed when I found this video.

[@marais75012]

Thanks a lot - I got one of these and feel confident enough now to go ahead and to the service job

[@arthurbradley4182]

Excellent work, j.P. Extremely informative. Thank you.

[@missyounorm33]

Great info. Inspired me to DIY my vintage 939 after watching this. Thanks

[@mstorrente]

Thank you very much Jordan. Very useful video for me restoring the dame unit. Very good explained and recordad. Thanks!

[@johnhornsby7578]

Just got a SX-838 a few days back. Mine was a lot cleaner inside it, but it had the same distorted channel due to the switches. Kept De-oxing and working the switches and it finally cleared up the audio, for now. Otherwise a really awesome receiver.

[@sand0077]

Great walkthroughl! This helps with servicing my SX-950 having no sound.

[@wilgo45]

Excellent video. Really picked up some high caliber pointers. Thanks

[@MultiTman1000]

Super info. Am fixing mine with this video information. My regulators 2SD313's were both intermittant. Solder joints were cracked, but when re-done the devices were still bad. Your recomendation for a replacement for the 2SD313 ( a TIP41CG) is also a nice pin for pin NPN transisitor replacement. Replaced panel fuse lamps with LED's Too much heat in this design. Am considering moving the power supply to the top of the chassis. Also indicator pointer is missing or broken off. When you get all done this thing is worth about 20 bucks, but oh well! It's easy to fix and cool vintage equipment anyway. And it has 2 phono inputs which most new recievers don't have any more.

[@jettramel]

Great Video on this models, I have a 636 so everything is not the same but it gave me some great tips on cleaning & problem areas like those blue caps used in older models. Great Video Jordan, thanks.

[@JordanPier]

James, one thing I have not updated on these videos deals with the failure of a transistor labled the 2sa726 or "a726" - which get leaky and cause bursts of static in the power amp on these machines. You need to replace the power amp transistors with matched pairs to keep the DC offset low. If your set doesn't have these symptoms those parts haven't failed yet. Just a heads up

[@skycarl]

Really good info on this JP,,, Thank you. Carl

[@jasonthewiczman5442]

Love your Video's they teach me so much

[@johnspina318]

I own an 838,939,and a 1010 and have done extensive rebuilding on all 3...Your video is phenomenal and I learned some cool trade secret stuff thx to this video..Thx Jordan.

[@montag4516]

I have a

[@montag4516]

Hi John, I have a 1010 that plays fine until after about 20 or 30 minutes the right channel output craps out. This can be temporarily remedied by cranking the volume knob up and down a few times, but eventually the problem returns. Any suggestions what I should replace first? Overall treble audio range is not very clear anymore. Both problems exist regardless of input source selected. Again, any suggestions? Thanks in advance.

[@solodolo6018]

​@montag4516 I know this is 4 years old but for anyone reading this I would clean all switches and pots with dexoit. Make sure to clean them well and exercise them at least 30 times. I just purchased an 838 that was sitting in a barn. Broufht it home turned it on and hardly got anything out of it. Cleaned all the pots and switches and it now works flawlessly. I actually had to clean the pots twice because I had volume dropping out and a weak channel still after the first cleaning. Hope this helps.

[@jeffturbert2196]

Great video. I just bought a 1010. Receiver sounds great. I'm having the typical problem with the darn buttons. I will load up on crc cleaner and deposit and be persistent. JP...you know your stuff.

[@msgetaways164]

Thanks so much . Just inherited my Father-in-law's 838 and it sounds pretty good, but you're right - the push button's are causing all the problems right now.

[@64dartgt273]

THANK YOU SO MUCH! This was the best video I have watched on this! I have a 1010 with those noisy pushbutton switches.

[@JordanPier]

You're welcome. Love that a body you've got pictured. My 1st car was a 74 dart, my second a 65 dart gt, my 3rd a 64 valiant 4spd small block, my 5th another 74 dart and 6th a 68 valiant. I couldnt stay away from them! Now money and time needs have had me sell them. Still regret it!

[@64dartgt273]

@@JordanPier Thank you so much! I have rescued 3 rust bucket '64 Darts and a '63. Those Darts are an amazing thing to have in common. My first car was my grandmother's '64 Polara, which made me a MOPAR guy. I have that car still and need to put it's re-ringed motor back in. TIME has indeed become more limited. So if you can advise: My 1010 from eBay responded well to the deoxit treatment as you marvelously demonstrated. It worked well for about 2 years and THEN, regardless of volume knob position or signal source, it started making a random LOUD crack/pop noise when simply powered on. I shelved it and miss it badly. I can solder and such but don't have an oscilloscope. Have multimeters. Any idea what might cause this? I am willing to try to fix it and love new skills. Cheers Sir!! Don. PS. I have an SX 434 and an 828 that initially worked ok for a year or 2 and then did the same thing. Luckily these didn't cost too much and I figured something would fail.

[@JordanPier]

@@64dartgt273 yank the jumpers for pre out main -in and see if it still occurs. If so the problem is in the power amp. Historically the 2sa726 transistors in the input section of the power amp get noisy and cause this. Replace with matched ksa992, 2sa970, 2sa1268 or similar. The 2sc1312 I believe is the npn counterpart which is used in the preamp and phono stage of these. Similar failures. Observe proper basing of transistors when replacing. Base and emitter is usually opposite modern basing on the old devices.

[@64dartgt273]

@@JordanPier THANK YOU! I love the blue displays of that era of Pioneers and want to try the 1010 with some Legacy Focus speakers that I inherited from my father recently.

[@rawtry65]

Another good job......

[@ovalwingnut]

Is this where I post my comment? I'm new here.... What I can say is: GR8T SHOW. It's like i'm your neighbor and I can stay and watch as long as I keep a cork in it (sorry for that visual). Cheers!

[@jimmytowns2471]

Great vid, much appreciated. Need a little cleaner on that scope face tho. 👍

[@FireandFrostHVAC]

Hey, I recognize that antique Ohmite variac on your bench, I’ve got its twin on my bench... 😁

[@billmcdonald2436]

Just curious, what kind of signal did you feed into it to test with? I’ve tried a 1khz sign wave at .2v and it works ok but if I try anything with a lower frequency it seems like my scope won’t pick it up. Problem with my scope or am I doing something wrong? Thanks for your videos!

[@_Ramen-Vac_]

sheer encyclopedic knowledge of componentry, sheesh. I guess a hoss knows his meadow though.

[@audiogman5865]

Great video. Thanks for posting this. This was very helpful with the 838 I just bought. Which Pioneer model would you consider to be the most reliable and/or easy to clean/lube?

[@JordanPier]

737 is probably the most reliable in this series. The 850 is the most reliable in that series The 980 is the most reliable in that series. The 626 is the most reliable in that series.

[@vintagesouthern54]

Have you worked on the x2x series? It doesn't have the same type of switches. If you have what would the weak areas on that series be. I notice that they have the blue sanyo caps as well.

[@JordanPier]

vintagesouthern54 worked on the 20 series too. Other than the blue Sanyo caps, watch out for plastic screws holding heatsinks to power supply regulator transistors. They crumble, allowing the heatsink to fall off, short something out and cause regulator failure from overheating

[@kgsalvage6306]

I watched this video once before. Do you actually remember those Mouser part numbers on the 313 replacement or were you looking at the package. I wouldn't doubt you remember it. If so that's pretty amazing. 👍

[@xthehowlingwindx]

I purchased one on eBay and when I set it up to my new turntable and new speakers, the sound comes out super distorted and staticky. I live in Oklahoma and i can’t find anyone who repairs vintage receivers. Do you take outside work?

[@christophwjones]

Great video, is there any certain deox you use?

[@spiritualfood8493]

Hello Jordan, I just watched your repair video of the pioneer sx-839. I took an electronics course in grade 10. But that's it. I am starting to learn electronics repair because my "new" SX-838 worked for 10 minutes and then the sound started to switch on and off. I can keep it working if it is at low volume and the low frequency filter is on. When the receiver is turned on it waits a second then clicks on. When the system goes on and off I hear a similar clicking. The lights stay on during the problem when the sound goes on and off. 1. What might it be? 2. I am thinking of buying something cheap at Thrifty's to practice on. I really don't know how to solder circuit board components (though I do well with copper pipes). Should I even think of trying to replace caps etc with my inexperience? 3. Where are you located and could I hire you to fix my receiver? Tim

[@fitzpreacherfarm6826]

Hi Jordan, just picked up one of these that lights up but just pops through the speaker. I cleaned the power safety switch just as you did. I cleaned the switches as well. I’m not an electronics guy. I thought you might give me some direction on what to look for, if not that’s ok. Also are these worth fixing? Thanks for your videos, I really enjoy them.

[@JordanPier]

Pop in both speakers = power supply. Pop in one speaker regardless of volume = amplifier Pop in speaker or speakers that is effected by filter switches = bad caps in preamp

[@fitzpreacherfarm6826]

Jordan Pier thank you sir, no one works on this stuff around here anymore.

[@ivanradoslovic8229]

One question about testing those caps with VTVM: can i measure caps with proper ESR testing with same accuracy of showing the health of cap? Or is it better to have vtvm?

[@JordanPier]

Vom/vtvm is used to measure leakage. Esr requires its own meter to measure . The capacitor wizard is the best one to buy if you've got the money

[@mkmeggy2]

Hi I just want to mention that I really enjoy your channel. I just pick up the SX 780 unit from yard sale. The unit was dirty but has power on it. I have a question, the balance knob is not working. It is just not responding well. There is no in between, when I turn the knob. It goes on and off like a switch. It should change the output gradually but it is not. I also noticed that the right channel VU meter is slightly weaker than left channel. I do not have equipment to test it out, like pro, but I notice slight different in the sound, when I put head phone. Do you think it is issue with balance knob or just Vu meter? If you have any suggestion or tool that I can use like multi-meter (to check the output) Please let me know. TY.

[@JordanPier]

mkmeggy2 the balance controls have never been great on those. 1st thing to do is get a can of deoxit and treat the switches and controls with it. don't get any on the radio board or tuner assembly (thing with fins on it ) check sound again. if one side sounds funny with headphones and gets worse when connecting speakers the stk0050 for that channel may be defective. protection relay may also be bad, but if so that problem would go away if you crank it up on speakers

[@mkmeggy2]

Thank you so much for your comment. I will do that first and hopefully solve the issue. If that does not work How much do you think the professional will charge me to fit it?

[@JordanPier]

I would set aside about 150 if the stk0050 module is bad. Slightly less if not. If you're in the US I may be able to recommend someone close to you

[@mkmeggy2]

Thank you for your reply. I found the exact problem. I noticed that at low volume level I hear left channel, but no sound is coming from right channel. I mean at low low volume level. I could able to find the issue by using head phone. I will try to clean the balance and volume again with deox stuff. Mean time, I am located in MD near Baltimore, Do you know any place that I can drop the unit and get service? I prefer not to send the unit with postal services. I really enjoy your channel and thank so much of your time. I learned something new. have a great day.

[@MultiTman1000]

Jordan, On my dog unit the protection circuit relay is broken and the relay chatters for several seconds before it stops chatttering. Then both audio channels are super noisy and when you turn up the volume it causes the relay to chatter again and then the audio goes dead. Can't find a replacement at Mouser. The Pioneer part number is ASR-007-0. If I bypass the preamp stages with an audio source then the same situation, so the distortion is downstream of the inputs to the power amp, but with the protection ckt going crazy it's hard to troubleshoot without a scope.

[@JordanPier]

the chattering, noise and distortion all sound like a common point of failure. compare using the schematic, check voltages on the power supply board first. sounds like you have lacking or dirty power. if that's ok, then check for intermittent DC offset in one or more channels measured at the output of the amp. this will tell you whether it's an amp or protect circuit problem

[@victorsalcedo8127]

Jordan Pier it is very enjoyable and instructional your teaching technique. Very calm and good language . A truly professional.

[@Hondacber]

I like the part when he changes the fuse at about 5 minutes and 30 seconds into the video and when he turns on the amp he says ( LOOKS LIKE THE FUSE BLEW IMMEDIATELY )

[@mattgama3251]

Hi Jordan great video. Would I be ok using crc contact cleaner to clean the switches and knobs

[@JordanPier]

Yes, that will probably work fine.

[@tomdemaline5148]

J.P. I absolutely enjoy your videos on servicing vintage stereo equipment. I have a Pioneer SX-828 RECEIVERand I love it. However it cuts out on the left side very inconsistently but every time I use it. If I tap on the left side of the receiver near the main switch it comes back on but always sounds weaker than the right side. It’s been deoxit many times in the last year but to no avail. What do you think it could be? thank you

[@JordanPier]

Tha speaker selector switches wear out on these sadly. Try B or C speakers. If no improvement could also be the speaker protection relay. Tap on the relay with the top cover off and see if you can make the failure occurr

[@tomdemaline5148]

Jordan Pier Thank you so much I will try that. If failure doesn’t occur should I replace the entire switch?

[@JordanPier]

@@tomdemaline5148 only replace it if you have to. It's a time consuming pain and your only source for a replacement is a donor machine - which you have to hope had less wear than yours.

[@tomdemaline5148]

Jordan Pier I understand thank you so much

[@RedneckPunk]

The whole issue with mine was those push buttons. I deoxitted the shit out them and cycled them a couple hundred times and now I'm pissing my neighbors off with some BlackSabbath through my mach 1's and Cerwin Vega D5's..thanks for you in depth tutorial..if you happen to do a Realistic STA 2000D I'd be tuned in..

[@christophwjones]

I just bought a 939 and the push buttons are giving me problems. Thanks for the video

[@williamgunter5199]

I AM NEW TO AUDIO REPAIR. I'M REPAIRING THE SX 838. I SO FAR HAVE FOUND ONE OF THE TRANSISTORS IN THE SUPPLY SHORTED. I AM REPLACING BOTH WITH TIP41CG....MY QUESTION, ARE MICA INSULATORS AND HEAT SINK COMPOUND NECESSARY?

[@JordanPier]

Heatsink compound yes. Insulator no so long as there is no possibility transistor heatsink comes into contact with another voltage or ground potential

[@markadams4316]

Do you have a video replacing the push button switches??

[@gingerelvira6587]

My SX-1080 has a loose volume knob, what size of allen wrench fits the set screw? thx

[@JordanPier]

1.5 or 2 mm Allen key. Don't remember which

[@zafersadeque356]

Hi, I am new but want to request to re-explain how to adjust bias and offset in detail. What I found in the manual under the heading "Aligning the Power Amplifier Section" on page 21 is different than what you mentioned in the video. Can you describe detail, please? Thanks

[@JordanPier]

Offset is easy. Adjust the appropriate potrntiometer listed in the service manual for the channel under adjustment for 0 volts at the speaker terminals. As far as bias, I don't remember where I was measuring since this was quite some time ago. Just follow service manual procedure and proper leads that clip on so you don't risk blowing up the amp

[@jeremyglazierAITC]

I have an 838 that has a problem with the left channel going out. If I toggle the switches on the front it has some static and will cut out and then come back. Does that sound like it just needs to be cleaned? I'd love to send it to you but I'm in Iowa and would be nervous about it surviving the trip.

[@JordanPier]

Get some caig deoxit, and treat the switches and controls. This may very well solve your problem. If the left side drops at. Low volume after this service, see if cranking it up momentarily brings it back. If so the relay contacts need to be burnished with 1000-2000 grit sandpaper

[@jeremyglazierAITC]

Thanks for the help. I'll give this a shot and then see how she sounds.

[@polaris911]

How do you know all this stuff? Where did you learn it? I am interested in learning, fixing these old stereos is becoming a lost art. But I also don't want to shock myself. I have an SX-1010 I believe the relay is bad like yours.

[@JordanPier]

polaris911 I started young. I've had an obsession with electro-mechanical things since infancy. I was given equipment by returned navy techs on the condition I prove I could use it correctly. I read many books, bought broken stuff at yard sales, thrift shops, etc. I would figure out what went wrong, how to fix it, sell it and buy more stuff. hands on and good reading are the key. I learned from excellent techs, most of which are dead now. I took some courses in college but it was remedial at that point. read up on basic electronics theory, transistor and tube theories, how to use a multimeter or dmm, how not to electrocute yourself. start with basics like old table radios and work your way up. buy broken stuff, find out what's broken and apply your knowledge. it may take you a long time, but learn how stuff works, how to troubleshoot and repair what doesn't work. be persistent. tenacity is the key

[@jjohnson149]

If you could list your test equipment used. Thx

[@TheBigfoottrucker]

What would that cost em ? What city and state are you in ?

[@sissymarylen15741a]

Do you work on customer products? I have a sansui se 8x equalizer I need gone through. If any help would be greatly appreciated

[@JordanPier]

Sure. Visit repairaudio.com and click on the ship in option on the left. Read up and send it in!

[@audiogman5865]

Can you make a video on how to adjust the DC offset and Bias on the 838?

[@JordanPier]

Consult the service manual. There are instructions inside

[@marcosribeiro1252]

Hello, how are you? I need the output transistors and the Sansuo G5700 icitators. Would you have it for sale or would you know of any contacts? Here in Brazil I can't find them. I also need those two plates that come out of the price plate, and go to the dicipator, where the output transistors go. If you can please help me..

[@JordanPier]

Your best chance is to look on ebay for someone parting one out or to buy a parts machine.

[@johnbotelho257]

Jordan sir great video, I was wondering if you can help me with my SX-650 Stereo. My stereo lights started blinking then the stereo immediately shuts down. Every time I turn on the stereo it does the same thing . Any help would be appreciated.

[@JordanPier]

John Botelho can you be more specific with "shuts down"? - that's too broad. If the machine stays lit up otherwise, but no sound and the main lights aren't flickering I would look towards the regulated power supply. Likely the 12v fed to the tuner and protection circuit is giving you trouble. If you're really lucky it's a loose fuse under the bottom cover. If the receiver really shuts down I.E. goes completely off and dead, then the power switch is dying - which is pretty common these days. You can either find a donor switch from another 650 or 750 and swap it (bit of a chore) - or short across the switch and install a line cord switch capable of 3 amps or greater

[@johnbotelho257]

Thanks for responding so quickly, Jordan! When I turn on the stereo it works fine with the lights and sound. After a few seconds to a minute the lights start flickering and the system shuts down completely; just like there was a power outage. I can go back and turn it on again but it keeps shutting off completely.

[@JordanPier]

Sounds like a dead ringer for a bad power switch to me.

[@johnbotelho257]

How would I repair it myself?

[@JordanPier]

John Botelho unless you're ready to find a replacement, take apart the front panel, switch assembly, and replace the power switch (solder skills reqd.) - I would just install an inline cord switch (3amps +) and short across the switch (soldering reqd.)

[@williamgunter5199]

BY THE WAY THIS IS NOT MY EMAIL...HOW DO I SUBMIT THE PROPER ONE?

[@mikefriedman6394]

I totally bought the wrong lamps on ebay. They work in the circuit, but are not as bright as the other inputs. This receiver is older than my grandpa. Should I stay with these incandescents?

[@JordanPier]

The incandescents will maintain the look. Joseph Mirabella sells the right lamps (projectblk86) which are 8v 250ma For the dial and 8v 50ma 4.12mm for the status lamps.

[@juancasagrande4877]

Muy buen aporte excelente video , tengo el mismo equipo que presenta la falla que el rele se activa y desactiva , los fusibles están bien , podré tener un corto circuito en la etapa de potencia ??

[@JordanPier]

More often the protection circuit itself is to blame for this problem - but only if no loud noise is heard through the speaker when the relay deactivates. If you hear a popping noise through only one speaker an amplifier may be at fault. If both speakers at the same time then it may be a power supply problem

[@juancasagrande4877]

@@JordanPier Excelente.. voy a chequear esos sectores ,muchas gracias!! por tus comentarios , saludos desde Uruguay.

[@retrovintagething7013]

I was told by a tech that I can use wd-40. Is this true? My SX-434 sounds great but my SX-939 & SX-1010 sound horrible. Great vid. Thanks

[@JordanPier]

If he says to use wd-40, he's not a real tech.

[@bassblaster505]

around the 24 minute mark the audio becomes way off sync

[@ny718bx]

Where is your shop or is this just a hobby for you? I have an 838 and would love you to have a whirl at her 👍

[@JordanPier]

I both work for a company that specializes in vintage and do work in my spare time. I'm located in San diego.

[@ny718bx]

Jordan Pier I'm in Vegas and seriously need to get you my 828. If I give you my email can we discuss? ant718@gmail

[@ny718bx]

*838

[@JordanPier]

***** check your inbox

[@markfewtrell2198]

Ive a SX-737. So thanks for this. Similar?

[@JordanPier]

+Mark Fewtrell the service techniques are very similar on the 737.

[@markfewtrell2198]

Thanks Jordan both for the answer and the video.

[@vintagesouthern54]

Are you accepting work? I have a local tech but he really doesn't do much for changing caps. I have 2 of these sx-828. This is an area I would like to learn to do for myself. I really like your video. Thank so much.

[@JordanPier]

vintagesouthern54 you can send it to my workplace, see repairaudio.com

[@Trev0r98]

This is why I don't buy vintage audio gear. Don't need the headaches... who knows what components inside are bad, or will soon go bad. And sending the vintage gear off somewhere to get it restored costs an arm and a leg. And even then, something unforeseen can go wrong. I just let the '70s & '80s audio era go. It had its time and place, but it's long gone. I was a huge audiophile back then...but I don't feel like having pretty, dust-collecting museum pieces with pretty panel lights sitting around now... and I wouldn't listen to them anyway.

[@Android_Warrior]

Then why are you wasting your time watching this?

[@Trev0r98]

@@Android_Warrior 1.) I watch it for the nostalgia value. It's engaging. 2.) It's my time to waste.

[@Android_Warrior]

@@Trev0r98 : Nostagia is good and yes, you can waste your time.

[@Trev0r98]

@@Android_Warrior I didn't ask for your permission.

[@Android_Warrior]

@@Trev0r98 : Didn't requested or required also, have a good day.

[@bobburbeck2950]

omg wha a filthy dirty scope, it looks so bad please clean it.

[@stephensnyder8016]

hey Jordan can I send you my sx838 to be worked on.

[@JordanPier]

Funnel it through my work. Repairaudio.com

[@kennethiman2691]

Darn that is some dirty equipment! But gets the job done. And its "these" not "these ones".