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Pioneer SX-980, Circuit Protection Relay, Random Drop outs

R

RobertSX980

New Member
I'm hoping someone on here might be able to help.
I have a Pioneer SX-980 receiver in pretty good shape. The receiver worked great until I discovered my speaker wires shorted together and it caused the Pioneer overload protection relay to kick in when turning on the receiver. I replaced the speaker wires and my Pioneer would play music for just a short period before the overload relay would start cycling. Knowing that the wires and speakers were now good, I opened up my unit and started trouble shooting the overload protection board. Everything looked clean, but I replaced every cap on the board and replaced the two transistors. The receiver now will play for days or weeks without an issue, but occasionally it seems to randomly trigger the overload relay and starts doing an overload relay cycle. The receiver is not hot and I'm pushing below 10 watts most of the time.

Here is how it fails:
~1-2 weeks, no issues. Then overload protection relay starts clicking.
turn off receiver, wait until everything discharges.
~1 day, no issues. Then overload protection relay starts clicking.
turn off receiver, wait until everything discharges.
~4 hours, no issues. Then overload relay clicks again.
turn off receiver, wait until everything discharges.
~less than one hour before overload relay clicks again.

If I take the receiver offline for a week or so, and plug it back in, it starts back at the beginning and can go for many days before the relay fault.

Has anyone else had this type of issue?
Should I attempt to replace the relay?

As a note, I have this exact same issue on a Sansui 7070, from the same shorted wire. Both receivers have random relay clicking, so hoping that if I can fix one, I can fix the other. I love them like my family.
 
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Does it have a Sanyo blue 0.22uf ecap on the amp pcbs? if so change it to a film using 5mm lead spacing
 
AE Bob said:
I have also seen noisy Q8's (2SC869) on the driver PC board trigger random protect.
Click to expand...
I see the 2SC869 transistors. I'll try replacing the 0.22uF caps first, and then dig into these transistors if they might be failing. Thanks for the input! Hopefully one of these items will help me out. I've been struggling on this issue for a while.
 
On the Protection PCB AWM-124, Q2, 2SC1384, is known for this kind of random dropout as it ages. Replace with KSC2690AY.
 
rcs16 said:
Might as well change c869 with a ksc1845 while you are at it
Click to expand...
Parts are on order. Thanks for the feedback. I look forward to getting them and making the changes. I'll let you know how it goes! I've always loved these old receivers, I've had several for almost 30 years now and this is the first time I've ever really had any issues to fix. I felt like the Maytag repair man. Finally now I get to have some fun.
 
I received the components in from Digikey. I replaced the 0.22uF, caps first. The old .22uf caps measured in at .31uF and .28uF, a little over their 20% tolerance. The new film caps I put in were 0.22uF +/- 5% tol. I started the received back up and she's running well. I will have to work her for a while to see if the relay still drops out after a while.

I actually tried to replace the 2SC869 with the KSC1845, but I did not get the receiver relay to click on after powering on to start after doing this, so I switched back to the 2SC869 to test it with just the caps changed first. I noticed on the 2SC869 and KSC1845 that the pin-out on the TO-92 package was different (2SC869 pinout = b-c-e, while KSC1845 pinout = e-c-b), I made a mistake in my notes on the pinout and accidently put the incorrect legs in. I will have to retry this.
 
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You are 100% correct! I just checked my notes and I had written it down incorrectly on my paperwork when I was doing the install. The data sheet clearly states ecb. For some reason I wrote down ebc. Thanks for being a second set of eyes on this one. I really appreciate it!
 
Update, 09FEB22. I had replaced just the 0.22uF caps and the receiver suffered the same malady, several hours of good playing, then relay clicks. So next we move to the transistors.

I have now replaced the 2SC869 transistors on the amp boards with the KSC1845 transistors and the receiver seems to be playing ok for now (I've been running her off and on for a few days). The protection relay issue generally occurs after a few days or more of use and then quickly becomes an issue. Hopefully (knock on wood) the transistor swap does the trick. I'll keep testing and update if / when the issue returns.
 
RobertSX980 said:
Update, 09FEB22. I had replaced just the 0.22uF caps and the receiver suffered the same malady, several hours of good playing, then relay clicks. So next we move to the transistors.

I have now replaced the 2SC869 transistors on the amp boards with the KSC1845 transistors and the receiver seems to be playing ok for now (I've been running her off and on for a few days). The protection relay issue generally occurs after a few days or more of use and then quickly becomes an issue. Hopefully (knock on wood) the transistor swap does the trick. I'll keep testing and update if / when the issue returns.
Click to expand...

if new c869's doesn't do it, then it is Q1 2SA733 on the protect board, getting noisy. ksa992 is the swap.
sounds like a transistor is getting noisier as it warms up.
can diagnose with can of "air" (not freeze spray - TOO cold) to aggravate it or pacify it..
 
RobertSX980 said:
Update, 09FEB22. I had replaced just the 0.22uF caps and the receiver suffered the same malady, several hours of good playing, then relay clicks. So next we move to the transistors.

I have now replaced the 2SC869 transistors on the amp boards with the KSC1845 transistors and the receiver seems to be playing ok for now (I've been running her off and on for a few days). The protection relay issue generally occurs after a few days or more of use and then quickly becomes an issue. Hopefully (knock on wood) the transistor swap does the trick. I'll keep testing and update if / when the issue returns.
Click to expand...

12MAR22 update: in the past 4 weeks, I only had one evening of drop outs (about 2 weeks ago). Still very strange as I haven't changed anything since replacing the amp transistors. Will keep everyone updated on the future use.
 
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