Toasty transistors SX-V80

Pioneer!

Active Member
It doesn't look like I am the first person to get a hold of one of these recently. I saw a few threads regarding this particular unit from last month, but I want to make sure that I start on the right track here.

Anyways, as of right now, the computer inside the receiver isn't being all that reliable, it fails to boot often, and specific features are not working properly. The amp section seems relatively strong, offset is about -11mV at its highest, and the sound is fairly decent.

On the the computer issues the following issues I have noticed:
Will power on and put out static as the computer hasn't initialized, and sometimes boots fine, but with the below problems..
VU meters non-responsive
Tuner signal meter not working
Tuner lock works but I am not sure that it illuminates?
Auto tuning and stereo indicator won't illuminate.
(What is interesting is that besides the VU meter, all of those indicators are red in color)

I have done a good look over on the chips, they all seem like they should work fine. Most discrete components visually appear fine, with the exception of the transistors on the power supply board, these have caused a fair amount of scorching and the solder joints are looking pretty tired.

I'm thinking I should start by dressing up the poor solder joints and see what improves. There may be some Zeners and resistors that got baked as well. See photos:
DSC00963.JPG DSC00967.JPG

Long-term plans likely involve some improved thermal dissipation by way of fan or stick-on heatsinks.

I also need to locate a schematic if anyone knows where one is available, as I cant find it on HiFi Engine
 
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I can't go any further than I have flying blind. I've done some resoldering and that has changed absolutely nothing. I may have found the VU meter issue, which consists of a burnt component on the speaker selector board (again I don't know what any of this stuff is without a schematic, I can't see well enough to determine what the small things are). All of the transistors are cooking, I have a fan blowing on them to keep a stable temperature but even then it eventually overheats.

Any ideas? Still having all the same issues and I don't want to run it anymore without some direction. Thanks.

See image
IMAG0622.jpg
 
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I've found that two zeners for the computer power supply have gotten warm a few times, and the above resistor is related to metering, so in theory replacing that should sort out the tuner lock, signal meter, and VU meter.

The power on fault doesn't occur if the unit was just plugged in and powered up immediately, but will present the issue if you turn it off and back on while it is still plugged in. Could this be a symptom of failing zeners? As in, the diodes will work when cold, but start faulting when they have warmed up? It runs great if it's cooled off, and will run forever, but it has to fully cool off before it reboots correctly.
 
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This amp shares a service manual with the SX-V90. The only difference between the two is the power amp board (the power amp board on the SX-V80 is the same as the one in the Pioneer SX-8 and you are directed to that service manual if you need to troubleshoot it). I've got a PDF copy of the SX-V90 service manual -- let me know if you want me to email you a copy.

The power supply board on the SX-V80 (the one you've pictured above with all the heat sinks) runs very hot and at the very least should be recapped as you'll find lots of cooked caps (use good 105 degree caps). Change any burnt/discolored resistors, diodes and zeners while you're doing the board. You may find that this takes care of many of the problems yours is having.
 
This amp shares a service manual with the SX-V90. The only difference between the two is the power amp board (the power amp board on the SX-V80 is the same as the one in the Pioneer SX-8 and you are directed to that service manual if you need to troubleshoot it). I've got a PDF copy of the SX-V90 service manual -- let me know if you want me to email you a copy.

The power supply board on the SX-V80 (the one you've pictured above with all the heat sinks) runs very hot and at the very least should be recapped as you'll find lots of cooked caps (use good 105 degree caps). Change any burnt/discolored resistors, diodes and zeners while you're doing the board. You may find that this takes care of many of the problems yours is having.
 
Hello
I'm really New to this Forum, but have read much on it in the past.
At Present, I'm rebuilding a Pioneer SX-V80 and was in the hope that someone might be able to help me with a Service Manual for it, as the last one I tried to purchase and then download was corrupt and unreadable.
In Return I would be able to help anyone with Service Data for Aiwa, Akai, NAD, and Denon, as I service for a Local HiFi Shop who deals these brands.
Thanks so much --
 
I've found that two zeners for the computer power supply have gotten warm a few times, and the above resistor is related to metering, so in theory replacing that should sort out the tuner lock, signal meter, and VU meter.

The power on fault doesn't occur if the unit was just plugged in and powered up immediately, but will present the issue if you turn it off and back on while it is still plugged in. Could this be a symptom of failing zeners? As in, the diodes will work when cold, but start faulting when they have warmed up? It runs great if it's cooled off, and will run forever, but it has to fully cool off before it reboots correctly.
Try using a can of freeze spray, most cans have an adjustable spray nozzle, put it in the lowest setting and while it's warmed up, spray one diod, transistor, resistor or cap one at a time, that should help locate the defective part, worked well for me in the past, be sure your Receiver is plugged and warm, hope this helps
 
Did you ever get it running properly? I have a couple of 90's in the basement. A nightmare to work on because of all the computer related stuff and twisted cables. I will start up again someday and try to finish restoring or rebuilding mine but was turned off by build quality of the boards and intimidation factor. I saw that resistor on your photo and I think mine looked the same. Not burned out totally but should be replaced with a larger size to dissipate heat better. I doubt if your diodes and Zeners are bad but the electrolytic should all be replaced. This series has Pioneers Most Beautiful and large display of all the units in my opinion but I am a bit turned off by the computer related garbage and video stuff. This was the era when people might hook these up to their television perhaps in the days of Soul Train. I have noticed some odd issues also with Pioneer SX-7 computer junk. I have one that the computer won't turn intermittently even though relay clicks all the time and amp is fine. I will try to re-solder the small board near the power supply with all the twisted connectors. What a pain!! Pioneer engineers should be shamed for these computer controlled receivers what a horrible idea for an otherwise fair to good product. I say fair to good because circuit board is substandard to marginal and will lift traces easily.
 
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