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Pioneer VSX-501 Repair Recap Advice

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Hello. I posted this in two incorrect spots first so hopefully I found the right board lol


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I own a Pioneer VSX-501 that was given to me by my uncle years ago. I use it in my living room for television audio and as a general purpose multimedia player and it's worked well for many years but over the last year or so I've noticed an odd occurrence. When the receiver has been playing music or movie audio for an hour or so it sounds like the top end of the sound intermittently cuts out on BOTH channels with multiple inputs (I've noticed it on phono as well as cd and TV inputs). I can still hear the song or movie or whatever but the top end just cuts out and returns when it wants.. it seems to be temporarily fixed by cranking the volume all the way up for a second but that solution has become less and less effective over time.

It's not the worst problem but since I'm somewhat handy with a soldering iron and know how to read electrical drawings (more or less) I figured if it was something easily seen with the naked eye like a bad solder connection or something I could fix it myself but.. after looking at just about every solder connection I could see without removing all the ribbon cables (since that is a huge pain as is) and tearing it apart, the solder joints look good. At this point I am thinking there may be a bad capacitor or transistor(? Maybe? Those can go bad, right?). So I downloaded the service manual from archive.org and started scratching my head..

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I'm thinking since it's happening on both channels it could perhaps be something to do with the Audio Function Assembly or maybe the Power Supply Assembly. Or maybe even the Volume assembly! There are a ton of things to look at and I'm not sure where to start diagnosing x_x. I thought I could tackle this alone but I may be in slightly over my head. But this is also very interesting to me and I'm excited to learn more. If anyone has any troubleshooting advice I'd be very appreciative! I hope I don't just have to end up putting new capacitors in the whole thing or something o_O


Side view of receiver. Board closest to viewer and to the right is the Tuner, I believe. The one directly behind it with the two ribbon cables going over the top is the Audio Function Assembly.

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I believe this is the Amp Assembly(?)

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Power Supply Assembly

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Also here underneath the front speaker terminals.. probably should have moved that out of the way when I was taking this picture but I didn't think about it.

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Your graphics are not showing up.
You say this problem occurs after the unit has been working OK for an hour or so; that suggests to me that heat may be causing a failing part to act up; if the unit still functions normally at first I doubt it's a cold solder joint and it wouldn't necessarily be visible if it were--but anything's possible.
Here's one relatively simple thing to try first:
  1. Remove the cover but don't mess with any parts yet.
  2. Get yourself an aerosol can of freeze spray with the nozzle extension straw tube.
  3. Play something for an hour so you can hear the intermittent problem cutting in and out consistently.
  4. Start spraying parts individually including transistors, caps, solder joints etc.
  5. If this stops the problem, or if it cuts out completely, note which part you just froze and take it from there (e.g., replace bad part or junk this old unit if too expensive to fix).
If you're in love with this model I see working ones on eBay for well under a hundred bucks.
Good luck and keep on learning!
 
daybreak2350 said:
Your graphics are not showing up.
You say this problem occurs after the unit has been working OK for an hour or so; that suggests to me that heat may be causing a failing part to act up; if the unit still functions normally at first I doubt it's a cold solder joint and it wouldn't necessarily be visible if it were--but anything's possible.
Here's one relatively simple thing to try first:
  1. Remove the cover but don't mess with any parts yet.
  2. Get yourself an aerosol can of freeze spray with the nozzle extension straw tube.
  3. Play something for an hour so you can hear the intermittent problem cutting in and out consistently.
  4. Start spraying parts individually including transistors, caps, solder joints etc.
  5. If this stops the problem, or if it cuts out completely, note which part you just froze and take it from there (e.g., replace bad part or junk this old unit if too expensive to fix).
If you're in love with this model I see working ones on eBay for well under a hundred bucks.
Good luck and keep on learning!
Click to expand...

Thank you for letting me know. I copied it from another post which I requested be deleted so it makes sense the images would be gone. Oops!

I guess should I just start with one board, try to freeze some components with canned air and then if nothing happens move to the next one? Would it make sense to start at Power Supply and move on to Audio function or something? Also it happens more noticeably with some 95W Sansui speakers I use moreso than some newer lower wattage Pioneer bookshelf speakers. This receiver is rated for 100WPC when in Stereo mode so I figured the speakers shouldn't strain the receiver too much.. but maybe I'm wrong? Think my problem may be a symptom of using too beefy of speakers for this receiver?

And yeah I know this is a pretty cruddy receiver lol. I figured if I'm going to practice on something I probably should practice on a low value receiver than start with like an SX-980 or something :p

Baby steps!
 
  • Not compressed air, that's for blowing off dust and doesn't get real cold.
  • Google "freeze spray for electronics"; there are about six different freeze sprays made specifically for electronics, prices range from $18 on up. One example: "Super Cold 134 is a pure, non-flammable cold spray that is used primarily for diagnosing thermally intermittent problems with electronic devices." Not cheap, so it's part of the repair cost if you decide to try it.
  • Your problem is that the highs cut out, not the complete audio like an open circuit would cause. And all inputs including tuner seem to work. So I'd start with the preamp then amp sections first. Kinda sounds like a bad transistor.
I really don't know if speakers are causing this problem but I doubt it.
 
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