Pioneer Spec4 Need Help

I started with the big 2200uf 100v and turned it on let it idle on the bench for 5 minutes than pulled the left amp and replaced all the caps and transistors and turned down VR2 to minimum and installed back in the amp fired it up on the DBT and set VR1 and VR2 than turned down VR2 and shut it off. Turned it on to full120v and set VR1 to 0mv and set VR2 to 50mv . Than I did the same thing to the right amp at this point both amp boards are back in and adjusted I was going to let it idle for 15 to 20 minutes to re check but after 2 or 3 minutes the 48v amp board relays kick off . I found that pin #1 on the meter board lost the 48v found a bad resistor R40 470ohm 2watt replaced and now it has 48v on pin 1 but when it is power on for 6 or 7 seconds it drops off . I took the right amp board out and fired it up with just the left in 6 or 7 seconds the relay closed and it worked knowing that left board worked it tried in the right after 6 or 7 seconds it lost the 48v on pin 1 on the meter amp board.

Both boards work if I put them on the left side neither of them will work on the right side . I took some measurements on the Meter amp AWM-113 and found no power coming out of pin 6 that goes to pin 10 on the right AWH-065 power amp board

Pins
1 46.9v
2 69.0v
3 69.0v
4 Ground
5 93.5V
6 0.001v
7 -0.065v
8 0.005 Right Meter
9 0.005 Right Meter
10 0.642v
11 19.94v
12 -0.015v
13 -0.061v
14 -0.002v
15 Ground
16 0.005 Left Meter
17 0.005 Left Meter
18 -69.2v
19 -69.2v
20 Ground
21 93.5v

Sawdust, There's a Meter amp board AWM-113 2/2 in the set and the +-90 supply's run to it. The board then regulates the voltage down to -68v off of pins 18 and 19. Both Main amp boards get the regulated from that board, so it may only be a broken wire or trace near or on the meter board AWM-113 2/2 pins 18 - 19.

Zeb

I get the 68v to both sides it's the 48v to close the speaker relay That I lose only on the right side when I disconnect the right side the left board relay will work I know it's not the power amps because they both work in the left side.

I can't figure out what is causing the right side to not close the speaker relays the left side only works when I disconnect the right amp.

The 48v for the relay supply comes from the other meter board AWM-113 2/2 pin 1. One meter board is housed in the meter assy. The one that provides the regulated is the smaller 2/2 board. I think I am back on track.

The meter board AWM-113 1/2 is the protection side and provides the ground for the relay's. I'm thinking; still, a broken wire or something like that. Not the original thought but same symptom.
Either a: Broken 48v supplies to the main amp boards pin's 9, from pin 1 of the 2/2 meter board. Or a broken return path from the main amp boards, pin's 8 to pin 10 of the big meter board AWM-113 1/2.

Trace the wires and verify the routing.

checked all the wires and cleaned all the connections every wire has good continuity . Both the power amps worked fine for a few minutes than both speaker relays clicked off only the left amp board will work but I half to disconnect the right amp board . I think it is something in the meter board putting the right side in protection. I have spent a few days on this and it time for me to get some input to get me on track

this is the easiest piece to trace the wires I have checked all of them at least 3 times

If it was that easy you would of had it sorted. I see the problem. No matter what, the set works only when the right board is disconnected. And both boards work in the left position.
I'm still looking at it.

I thought the meter board was two boards but its one big one.
With both boards plugged in and the set on, what readings do you get at pins 12 and 13 of the meter board (DC w/ chassis ground)?
Checking the protection inputs from the amps.

Edit - zeb's reading instructions are good too - while doing them with both boards in, do the pin 8 9 and (across )R7 readings...

First: Check your pin 3 pin 5 and pin 21 earth connections for the right (and left) sides. Sockets must be empty when doing this resistance check.


Symptoms - both amp boards work in the left channel position, but not in the right - WITH THE LEFT INSTALLED.

See if the right board position works solo (like the left). Test with both boards.

during the test:
make ground based voltage measurements of amp board pins 9 & 8 with just the left board, then pins 9(+48v side) & 8(gnd side) with left and right boards.

You see, Q7 on the meter amp assembly pin 1 provides the +48v (pin 9) for both relays, and may not be up to it (the +48v falls off under attempted operation).
OR
pin 8 is the "bottom" of the relay, which is grounded to operate, and this is through pin 10 of the meter board to an UNDERSIZED Q13 2sc1384 that may be weak.

Have you changed Q7? Q13? either of the relays?

Finally, during the failure, please read the voltage ACROSS the new 470 ohm 2 watt resistor feeding Q7.

hooked the right board back up took readings

PIN 12 0.010v
PIN 13 0.060v

not enough to put into protect. i.e. leave the relay un-actuated.

please do the pin 8 ,9 and across 470 ohm resistor's voltage readings.

this is unlikely. but another possibility for operating the protect is the pin 1 over current inputs/outputs that are paralleled and pulled to ground during a fault.

one being leaky doesn't clear the threshold, but BOTH might. did you do anything with q12 (2sc869) or C24 (0.22uf a dreaded sky blue sanyo) on each amp board?

Mark

I did change Q7, 2SC945: 512-KSC945CYTA and Q13, 2SC945: 512-KSC945CYTA and did the Echo Wars mod on the 48v relays on the power amp boards. and Q12: 2SC869: 512-KSC2383YTA

I did pull and check Q1 Q3 Q7 Q26 on the meter board all tested good the 470 ohm tested 492 ohms I soldered 5 100ohm resistors in series I got more coming from mouser tomorrow 470 ohm 2w

I used mattsd parts list I replaced all the caps and transistors even the out puts on the power amp boards

EDIT - WOW, NICE JOB!!!

OK, two new 48v relays being driven. 19 mA apiece...

awm-113 q7 on the meter amp assembly is a power transistor 2sd381
awm-113 q13 on the meter amp assembly is a 2sc1381, as I mentioned before.

re: awm-113 meter board tests, they would test ok, until under load, heating up, and failing - especially the undersized awm-113 q13.

I really really really need those voltage readings under the test conditions I detailed.

did this unit work for you before you started all this?

I did test both boards in the right side and they did not work left side was empty

yes it did work before

ok, neither will work when connected into that particular position.

work as defined by relay pulling in.

need to do this first

First: Check your pin 3 pin 5 and pin 21 to earth connections for the right side. Connectors must be empty when doing this resistance check.

Click to expand...

still need voltage measurements. one set with board in left position and working
other set of readings with board in right position and not working.

awh-065 pin 8 to ground
awh-065 pin 9 to ground

also voltage across awm-113 R40 470 ohm 2 watt resistor.


we have covered ALL kinds of other stuff, all but WHAT I NEED THE MOST!!...

measuring across the 470 ohm resistor with both amp hooked up starts to drop as soon as it is powered on and goes to OL in 5 seconds


just to remind you I still only have one good wing so I am down to one finger to type with