Pioneer SX-828 with serious issues/short circuit and blowing fuse every time.

[@frankscarano4708]

As a tech very experienced with Pioneer and these models myself I wanted to point out some stuff. One of the things ive seen here and units i get that have been worked on that a lot of techs overlook is the small signal transistor issues these pioneer units have. The differential pairs on the amp side are known for issues as well as the phono, line, and tone stages. All those small TO-92 guys that have black oxidized leads often develop hiss and crackling and are in actuality more important to change than even most of the electrolytic capacitors. I especially find these become noisy in the phono stage being they are used for very high gain stage amplification. The caps are always a good idea still.. Also on the 828 There are Two regulators on the power supply board held in with nylon screws to a rectangular bent aluminum heatsink. these nylon screws become brittle and break and the heatsink just comes off and away from the transistor. I always at minimum on the 828 replace the screws with new nylon screws and change the insulator ( they often become stuck to the heatsink and transistor and add thermal compound. If they are using sanyo made TO-220 transistors i replace them as well with KSC2073 for the two that are on there. I also want to point out that the MJ21195/96 where as it will work are meant for higher power applications. You could easily use MJ15001,15002, 3, 4 and even MJ21193/94 as well in the future ( if you have them) and still have more than enough power bandwidth.

[@shamansshaman1823]

I appreciate your detailed analysis and explanations of everything you do in repairing these receivers. You are by far the best on KZbin in your videos since you take time to show all aspects of your repairing these units. Others skip out on many steps in their videos. Please continue your fine work. If possible, do a Marantz 2027! Thanks.

[@VintageAudioFever]

Shaman... God bless yeah!!! Your comment was truly appreciated... Thank you!!!

[@VintageAudioFever]

If 2027 M comes to my bench, I'll make sure we do the video together for sure...

[@marais75012]

That was very instructive. I happen to have an 828 on the bench right now, and I found similar issues on the power supply board.

[@maxred222]

I’ve watched a lot of these audio repair channels. You are one of the best, if not the best out there. Your detailed explanations are fantastic. The subs are inexplainable. Thank you.

[@Reflectiveness]

I enjoy watching a long-lasting restoration.

[@user-px5ew7iq5r]

Great video sir, thank you for sharing. i enjoy watching your expert tutorials. im a noob learning a lot of technique from the master at work. ❤

[@carolynmaxwell-hc4co]

Thanks Joe.....Another excellent diagnostic job. It just shows how important it is to look further back in the circuit to find the root cause for failures. I am very pleased with your thoroughness approach to the overall job. I look forward to listening to this receiver, when I get home.

[@VintageAudioFever]

thanks Tim, when you get better soon I hope, let us know how she sounds...

[@nudebaboon4874]

Great work Joe, hope you get a lot more subs!👍

[@TrevorsBench]

Hi Joe, Those burnt resistors on the amp board are in series with a capacitor. They form the zobel network. They likely burned up by the user pumping high frequency, high power signal through the amp

[@VintageAudioFever]

Hey Trevors, yeah..makes sense, I never thought of those 10 ohms resistors being effected also would certainly be in serie with that cap....GOOD point!!! PS. I mention you in this video, hope you didn't mind...

[@TrevorsBench]

@@VintageAudioFever No problem, thanks for the shout out. I don't always enjoy repairing switches but it can be satisfying

[@MrArt542]

Hey thanks for this great tutorial video and tou break down everything till you find the source. I've been a fan of these classic Stereo Amplifier. I have a Kenwood Stereo integrate Amplifier its a monster. Not to long ago a friend of my gave me an Parasound HCA-500 and I noticed that the fuse from the power supply 1Amp. 250v blow out and serching to send this to be fix soon.

[@JamesE707]

Most folk do not realise that 'fixing' a deck or an amp is often one fix after the other. Many many hours gone into this one Joe! - nice work buddy!

[@VintageAudioFever]

Well said!

[@johncooper6246]

Just really enjoy your attention in testing caps and setting up the bias voltages. Man I dig the turntable as a pain in the ass saver, cheers

[@martinkoskella3943]

Another great repair. Good pace and explanation of faults and resolutions. Good catch on the capacitor, must have been the root cause of power transistors shorting.

[@JamesE707]

Those relays labelled ASP-007 (from the SM) quite possibly saved his speakers too.

[@ronaldfriedline9297]

Just purchased an sx 828. Seems to working well, but makes me wonder what secrets are lurking under the hood.

[@mistermac56]

Great repair video as always Joe. Enjoyed how you already tested that the left channel output transistors were dead and the source of the issue, but you went through the steps diagnosing the issue to prove your hypothesis. When I was a tech for a local Panasonic service center back in the 80's-90's, their name for it for us techs was the fancy term "Fault Tree Analysis."

[@bobdoritique7347]

Merci, very cool and pleasant this video.

[@VintageAudioFever]

Glad you enjoyed it!

[@yambo59]

Hi - I sure wish I had a tech like you were I live in Illinois id be glad to pay you well, I have a nice clean Pioneer SX-1080 that still works ok that I would love to restore but has all its original caps etc. and im afraid to keep using it and do more damage. I hate all the black plastic junk that took over after the really nice quality stuff from back in the 70's and early 80's - all the really good audio restoration / repair shops have folded here - the ones left dont want projects they just want quick turnaround flat screens, video games and other throw away crap. - yeah im an old guy (65) and I miss the well made gear from back in the day.

[@VintageAudioFever]

Thanks for sharing your experience and appreciation for older equipment! It's funny, I love working on older amp more...so much easy to repair... Ps...65 is not old.

[@steveoszman8746]

Joe you convinced me to use a power strip, just bought a sansui au of that era. I looked at that on/off + speak selector and said to myself that rube goldberg thing lasted 49 years. Thank you what you stated is saving me later regret. Dogs marbles pretty those old pioneers.

[@johncunningham5435]

I bought a second hand Pioneer SA-1000 amplifier, the seller claimed it had been serviced, the only claim that was correct, flawless condition. There have been a number of issues that have slowly been addressed, but, I still have a lot of work to do. The layout is very similar to the Pioneer SX-828, even down to the on/off power/speaker selector. Joe! your video was very informative, giving me some fresh idea's on servicing.

[@VintageAudioFever]

Thanks for sharing

[@Jon-zr5om]

I kept thinking, I hope he sets the bias to those new packs lol Good job M8

[@VintageAudioFever]

haha I wouldn't of miss the opportunity on the bias test....

[@JamesE707]

Regarding complimentary push-pull transistors and their bias currents - this does tend to drift somewhat because of component thermal drifting and amplifier usage. Anywhere around 20mV was perfect Joe! ;o)

[@johnny7254]

Joe - your videos are getting better as you let your personality come through

[@VintageAudioFever]

truly appreciate your comment....thank you

[@VintageAudioFever]

Awww thank-you

[@sajusebastian4991]

Joe I found your channel accidentally.Nice job.Greetings from Vienna Austria.An Indian technician settled in Austria.You are always wearing the gloves because you are a paramedic?Just kidding.😅

[@sajusebastian4991]

Subscribed

[@VintageAudioFever]

Love my gloves 😍

[@JamesE707]

This weighs in at around 15Kg!

[@JamesE707]

I watched it all the way through - top stuff!

[@VintageAudioFever]

thank you James....

[@Daltondoubledeuce]

Great work Joe!

[@VintageAudioFever]

Thanks!

[@franz7227]

Bravissimo Joe 👍questi sintoamplificatori li adoro.Saluti dall'Italia 👋

[@VintageAudioFever]

thank you Franz....appreciate your comment.

[@g.fortin3228]

Very good and thanks for the tutorial on watching caps that could take out transistors ! I had not realized this..but totally makes sense.

[@gem1967]

You really impress me. I wonder if you are close to me. I'm in central PA. I got a Kenwood KR 9600 that needs work. Will cost alot to ship( I believe 54lbs?) . I have alot of parts for it. Light kit, cap kit, outputs and a speaker terminal board. Needs a cleaning of controls too.

[@VintageAudioFever]

I don't live near you unfortunately...

[@AstrosElectronicsLab]

It's very doubtful that the 1000uF caused the transistors to short. Transistors will work fine on badly/unfiltered DC. Probable causes are as follows: you need to ask yourself what did the owner DO? As I haven't studied the schematic at all, I'm not sure if Pioneer employed VI limiting on the power amps (for this vintage, probably not). If the speaker terminals were shorted together, and the fuses didn't blow, it's possible (especially TO3's) to blow the junction(s). Other causes could be age of the TO3 devices, they just gave up the ghost, and the final cause is exceeding the SOA (safe operating area) of the transistors by overheating them. The latter is doubtful, assuming the unit just turned on, he turned a switch and the fuse blew. Final thoughts, most class-AB amplifiers will work fine with a quiescent current of 35-60mA depending on output power. Easy way is to put it on a scope (with a timebase set so you can see only one complete cycle on the screen) with a signal injected of 1kHz at around, I don't know, half power, and just adjust the pot to get rid of the notch at the 0 point (cross-over distortion), and then tweak it a little higher after that. Or, set it to 35mA, scope it and see if it's clean and go from there (this is if the service manual doesn't give you the bias adjustment information, or you can't even find the service manual).

[@transformateur9969]

Thank you very much sir ! Very interesting !

[@VintageAudioFever]

I'm glad you like mon ami...

[@transformateur9969]

@@VintageAudioFever Bonjour Joe , êtes-vous du Canada ? Je suis de Saint-Georges Québec

[@alexzildjian]

Muchas gracias ☺️🙏

[@MrElectrowhiz]

I want to make a correction to one of your terms that you used. The clear item between the output transistors and the heat sink is MICA insulators. Thank you for your video

[@VintageAudioFever]

well thank you for correcting that for sure....'micro insulator' sound so much cooler...😉

[@johnsampson1096]

Good content as always, Joe! Glad you can stay on your feet while servicing. Technicians can get slightly lazy and out of shape from working chairside, myself included. My brother in law used to sit in business meetings endlessly, until the chairs were removed from the conference room. Two hour conferences then only lasted 45 minutes! I love keeping these classic pieces out of the landfills. Amazing how one or two components can be the cause. Cheers..................

[@VintageAudioFever]

on my feet or on my toes always ...thank you!!

[@SymbolTech21]

Hi Joe, you should get a function signal generator will be more accurate for testing these amplifiers, also you can do a sweep and see the frequency response of the amplifier

[@MuhammadAbid-e8k]

Great work Joe. I have a question though, why is there a thin sheet of plastic probably between the transistor and the heatsink? Doesn't that plastic sheet or film prohibits the heat flow and reduced the heat dissipation ? Is it for this reason that the transistor heated up and got blown ?

[@VintageAudioFever]

Hi Maha....thank you for your comment, the plastic shield I think you are refuring to is called a mica transparent insulator, the main reason for this insulator is to isolate the transistor from touching the heatsink that would cause a short and short out your transistor and yes the TO-3 transistor can get hot and that is why you need to put some thermal paste between the transistor and the insulator to dissipate the heat and help stop the transistor from overheating.

[@MuhammadAbid-e8k]

@@VintageAudioFever Thank you for the reply. This seems very inefficient in removing the heat. I wonder if new systems are also build in this same manner? Or if new technology has invented better ways of doing the same thing ?

[@jefftobin4034]

Nice video. I guess there's no telling which failed first, the capacitor, which migh put ripple on the negative rail, stressing the output transistors(?), or one of the output transistors, which would draw enough current to eat up the capacitor a great deal, I surmise. I would bet on the transistor(s) being the cause. Otherwise both channels would should have seen the same stresses to the output transistors.

[@VintageAudioFever]

Great point! What I was thinking was more of a capacitor as it was getting weaker/dryer etc...this 1000uf been bad for a while I'm sure... All of Our ideas and thoughts makes alot of sense though...makes us think and learn same time...

[@gregnewberry4813]

Great video and trouble shooting! Where did you get those long clip on probes you used setting the bias? Thanks

[@VintageAudioFever]

Hi Greg, I bought those long clips from a electronic shop near me but you can also buy on amazon...happy shopping

[@collinwood60]

Joe, how did you fix that lifted trace? Always want to know the best way to fix those as its happened to me a few times in the past. Another informative repair. Looking forward to the next one.

[@VintageAudioFever]

Hey Collin, I will show how I do repair damaged trace in my next video...

[@JonPaul]

Hiyas. Ya, I've had toasty resistors flake apart like that but still read within spec. I recently got sidetracked on a repair by an output that passed the diode test but curve tracing showed basically a flat line. Diode test is good 90% of the time, but not 100%. I have to admit, I'm not crazy about your inboard go o go tests. But I'm just some guy on the internet, you know? :) I like your use of gloves, especially with that strong of IPA. I just bought an ultrasonic cleaner, I'm gonna try putting some boards\controls in there for cleaning. I suppose I'll have to regrease control shafts, gloves will be good for all this. HOLY CRAP on the power switch! Fingers crossed that I never experience that, I can't imagine the difficulty of getting all those contacts lined back up. LOL< I'm laughing on this one, you got RED FACED just talking about it! Hey, I'm recently retired as well, so watch what you say! :) Nuff said.

[@VintageAudioFever]

Hi Jon haha @ retirement...I'm not there yet but I should.. I will hope to see your repairs on YT..God knows we need more of US...and yes..I didn't like the idea of that switch coming apart like that... can you elaborate on my inboard go/no go tests? it would be nice to have your input as im not sure I understand ... last but not least, thank you for watching my videos and I do appreciate your comments...

[@JonPaul]

@@VintageAudioFever I'm being too critical and the go o-go is great for troubleshooting a non-working unit. I have the time and don't do repairs for a living so I have time to pull and test (and generally replace) many components and I've found so many components that were far out of spec but of course would have passed the inboard go o-go test. Don't listen too much to what I say, I'm still salty about a Kenwood KA-3500 with an intermittent snap\crackle\pop on which I wasted so much time - I should have immediately started pulling and curve testing transistors. Over the years, I've sure learned that vintage audio is VERY forgiving, especially for many capacitor values. So ya, carry on and don't listen to random guys on the internet. :)

[@marka1986]

An octopus tracer is nice for this. Helps spot marginal devices. Just that little c to e leakage you never see with a meter or when the B to E junction looks more like a recliner than a chair it's one to replace.

[@JonPaul]

@@VintageAudioFever I didn't reply to your comment about repair videos. I have to admit, I don't think I could produce a decent video of a repair. I am always impressed when people like you not only do the repair but the complete video as well.

[@JamesE707]

@21:25, that capacitor is only rated at 10v - why didn't Pioneer use a cap with at least double rating? I've seen this so many times - often cap rating (before theoretical breakdown) are so close to the operating voltages. No need for it? Cost may be?

[@VintageAudioFever]

I've often wonder the same question in why would they use a capacitor so close to the voltage needed, it must be cost I guess... I don't think pioneer meant for their receivers/amplifier lasting this long....

[@MrChrisRP]

@@VintageAudioFeverTheir behavior varies with respect on how far away they are operating compared to their rating. In other words, the way they operate with respect to certain characteristics might be more desitable to the design engineer when operating close to the rating. This is on average and every product and line of capacitor is different.

[@billfox6478]

Hi Joe! Could I get your contact info? I’m in the Fredericton area. I have an Amp that need some love. Cheers

[@VintageAudioFever]

you found me!!! c\see you soon.