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Pioneer SA-8100 Half volume protection

I spoke to soon.....thought I was in the clear. All diodes soldered back in, Q6 replaced. Does not go into protection now, BUT on power down, with volume turned all the way down, I get a very pronounced thump in the speakers. Sounds like it is timed to the relay. This is new. It is the same with the volume turned up or all the way down.

I would say it is related to Q6 replacement, as before the replacement there was no thump upon turning off the 8100.

Again, thanks in advance.
 
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redo the fuse test. you may have damaged q6, or even q5.

not going into protection and turnoff thump = that stage not working. :no:

The time delay is exclusively q7.
 
Went back through, Q6 and fuse test. Replaced Q6 (Which had perviously been put in Q5 location earlier - OOOPS!) - good catch Mark, with new KSC2383YTA - pop/thump is gone when turning off unit.

So I think we are all good.

Replaced all transistors - with the exception of Q5 (NEC SA733Q24Z).
Replaced all caps - including .22uf caps

Just curious - what would be a good replacement for Q5?

Mark appreciate your patience and catching my screw up on Q5 and Q6.
 
I feel like I'm chasing my tail! Thump is gone, but we are back to 1/2 volume = protection.

Going to test right and left sides - see if one side trips and not the other.

Then will do the fuse test and lifting of the diode test. Will post those results
 
Spent some more time on the 8100 this afternoon. Here is what I accomplished (or not!)

Tested today:

1AMP fuse test - lift one end of fuse - immediate protection
Input Aux 2
Speakers connected - protection at 50% volume
Speakers disconnected - protection at 50% volume
Balance test - right and left trip -same protection around 50%
D5,D6,D7 Lifted - No protection trip
D6,D7 connected D5 Lifted Only - No protection trip

Today - D1,D2,D3,D4 - New -1N4148
Today - Q6 - New - 2383 - Replaced second time original damaged due to my stupidity in Q5 location

Previously - in last week
Q3,Q4 - New - SC1845
Q1,Q2 - New - SC1845
Q5 - Original - 2SA733
C1,C2 - New .22 Panasonic Mylar
C6 - New - 10uf 35v
C5 - New - 4.7uf 50v
C4,C8 - New - 330uf 10v

As of today: At this point the unit goes into protection around 50% volume, with or without speakers connected.

Is there a possibility that the protection circuit is working correctly and there is another issue? In my mind I see this dog chasing his tale - round and round
 
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put d5 in, remove q1, try

then put back q1 and remove q2.

try again. we do not want to infer the trip, we must prove it by it's presence.

removing q1 or q2 defeats that circuit, not the problem...

test all the resistors (with one end lifted)around the transistor that trips, also check on the amp board that is connected to those pins.

you did test and set idle current on each channel?
 
D5 in
Q1 out - Q2 in - volume up = protection
Q2 out - Q1 in - volume up = protection

Idle current between 1 & 2 =.022v Neg Lead on 1
Idle current between 24 & 25 = .021v Neg Lead on 25

Neutral Position between 3 & Ground = .002v
Neutral Position between 23 & Ground = .001v

Starting to doubt my work. C1&C2 are panasonic film caps - markings are 13L 224 - .22uf 50v. I do have more of the panasonic film caps

Since I got protection with either Q1 or Q2 out, I'll check all of the resistors.......
Looks like about 8 resistors to check between the Q1 & Q2 - will get to that tomorrow - might get lucky and find a few bad resistors...........doubtful but hey anything is possible?


Thanks again for your patience.
 
q1 and q2 were originally 2sc857
replaced with ksc1845

the ksc1845 are emitter collector base layouts, with leads pointing down, letteriing facing you and going from left to right.

Leave d5 in, but pull q1 AND q2, and be sure it doesn't trip.

we may have a bad foil path somewhere. It does go over to a blind pin... and some crud could be shorting it.

If the transistors are installed correctly, post some pictures of the board top and bottom.
 
Man do I feel like a butt. I'm at work and pulled up the image on the first post or two. Nice clear picture of Q1 & Q2. KSC1845 transistors ECB left to right.

So what do I see? Q1 and Q2 are in wrong!
Transistor E in board B, C in C and B in E. At least that is what is printed on the board. I swear I checked and double checked.

So it looks like I have Q1 and Q2 in wrong - I'll find out this evening.
 
I am a butt! I swear I had checked and rechecked Q1 and Q2. Replaced the incorrectly installed Q1 and Q2 with a new set of KSC1845's. And now, no issues.

Although I can't keep it above 50% volume - I'll go deaf- it plays at above 50% without protection. No thump on turn off. All is good.

Mark, so sorry for wasting so much of your time. I sincerely appreciate your patience and your amazing understanding and knowledge of the vintage audio gear.

Thanks again!
 
I learned quite a bit with markthefixers help. The most important thing I learned - check and double check, then check again - especially with transistors!
 
Do the checking with fresh eyes when tired, assume nothing - and I do EXACTLY that for my "last checkout" of each board, and sometimes it WASN'T the LAST checkout as I thought it was. This is BEFORE I ever re-apply power after mucking about inside of anything. It generally rewards my efforts by working.
 
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