Pioneer SA9100 Power amp Assembly problem

super88394

New Member
Just picked up this amp from a fella who said one day a little puff of smoke came from the left side and it blew the main fuse and stopped working.
So upon checking it over the left side, I removed the Power Amp board awh-023c, and found a fried board between pins 13 and 15. (see pic)

My question is this, what is the best way to proceed in repairing the board (solder in a wire bridge or solder the copper together)

And what should I check while I have it out, or should i just rebuild the whole thing while its out?
 

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Is Q11 shorted, it's the PNP output transistor. If shorted that would put -45 VDC on that trace going to the protection board. Check the protection board for bad parts also.

Craig
 
You have problems in multiple locations, including the power amp board you have pictured, the output transistors and the protection board.

The "lightning bolt" that popped that foil MUST be traced from pin 13, to pin 5 of the protection board, and from pin 5 on the protection board to where it finally exited to ground.
That length of foil that exited on pin 13 of the amp board was never intended to carry that much current on that path.
The protection board is going to be a mess.

I'll bet that R9 (2.7k 1/4 watt) of the protection board is fried, Q1 is fried, all because C1 was actually a 0.22uf sky blue sanyo cap that shorted out.

You are going to have to do the full rebuild, PLUS additional search and repair, before even THINKING of applying power again,

There is going to be damage in SURPRISING places. That's why I called it the lightning bolt. I have seen damage in these areas cross over to the other channel of the power amp. As well as leaving unseen damage that is waiting for you to THINK you have it all fixed, to power it up, and wreak additional damage.

EVEN the 0.5 ohm emitter resistors are suspect.
 
someone has been in here before. The cap on the protection board (awm-025) has been changed to a new one. Looks like someone started a recap or just replaced a few.

However are there different manuals for this board? Mine lists .056 50V where on the board is .22. Also Q1 in the manual is 2sc857k-a and I have a transistor ending in c869 24c

Mark you say R9 (2.7K) but on the diagram R3 comes off pin 5 and reads 2.7k. I pulled R3 off and it reads 2.7k. and the transistor reads 750 mv uf in my little tester.

The 5w .5 resistor reads .7 I will replace with 71-CP5J-0.5
 
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ok so digging around I found my board is awm-025c, same layout as awm-062.

Replacement transistor for the 2SC869-C is 512-KSC1845EBU but is obsolete. can I use 512-KSC1845FTA? specs look the same
also
Q3, Q4 SSC945-Q 512-KSC945CLTA obsolete......512-KSC945YTA (new specs look the same)

Q5 2SA733-Q 512-KSA733CLTA obsolete.......512-KSA733CYTA (new specs look the same)

Q6 SSC945-Q 512-KSD1616ALBU obsolete ......512-KSD1616AYTA (new specs look the same)
 
use a992's for the a's and c1845's for the c's - don't phart around with the 945/733's.

KSD1616 use the
512-KSC2383YTA to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17

yes
512-KSC1845FTA

is the only one they have anymore (tears)
 
Ok I want to make sure I am on the same page so

Board AWM-025C

Q1 2sc869c sub 512-KSC1845FTA
Q2 2sc869c sub 512-KSC1845FTA
Q3 2sc945q sub 512-KSC1845FTA
Q4 2sc945q sub 512-KSC1845FTA
Q5 2sa733q sub 512-KSA992FBU
Q6 2sc945q sub 512-KSC1845FTA
Q7 2sc1384r sub 512-KSC1845FTA

now on the AWH023 board

Q1 2SA774A SUB 512-KSA992FBU
Q2 2SA774A SUB 512-KSA992FBU
Q3 2SC869D SUB 512-KSC1845FTA
Q4 2SC869D SUB 512-KSC1845FTA
Q5 2SA628A SUB 512-KSA992FBU

Q6 2SC1451 SUB 512-KSC3503DSTU ?
Q7 2SC1451 SUB 512-KSC3503DSTU ?
Q8 2SD358 SUB 512-KSC2690AYS
Q9 2SB528 SUB 512-KSA1220AYS ?

Q10 2SC1079R SUB 863-MJ21194G
Q11 2SA679R SUB 863-MJ21993G


Now on a full rebuild of boards, I will want to to all diodes and all resistors as well ? That would be a full rebuild.
 
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arrrrgh no
use the
512-KSC2383YTA to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17 for awm-025c q6
and the ksc2690 for awm-025c q7

no resistors, diodes could be done if you want, 512-1n4148 or 512-1n4004 depending...

get an extra 1n4004 and it will go between pins 9 and 10 (banded end) of the awm-025 - a mandatory upgrade.

edit - pin 10 is banded end - I was tired and in a hurry and made an error.
 
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arrrrgh no
use the
512-KSC2383YTA to-92L ecb 160v 1a .9w 50mhz 160-320hfe $0.17 for awm-025c q6
and the ksc2690 for awm-025c q7

no resistors, diodes could be done if you want, 512-1n4148 or 512-1n4004 depending...

get an extra 1n4004 and it will go between pins 9(banded end) and 10 of the awm-025 - a mandatory upgrade.


Thank you, parts are on order....see you all in 2 weeks or so
 
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get an extra 1n4004 and it will go between pins 9(banded end) and 10 of the awm-025 - a mandatory upgrade

I'm probably going to embarrass myself here but should the banded end go to pin 10 (34V from relay) and the anode to pin 9 (8V from relay)?
 
I'm probably going to embarrass myself here but should the banded end go to pin 10 (34V from relay) and the anode to pin 9 (8V from relay)?


You are correct - no embarrassment, GOOD catch - I was tired...

YES: banded end go to pin 10 (34V from relay) and the anode to pin 9

it's now fixed in everything but the quote in his post

the wrong way will damage the regulated supply pulling around 100 mA. (r24 180 ohms 1/2 watt in the power supply makes the +35 from +42 and at 100mA it is dissipating 1.8 watts and would pop) due to the 220 ohm r28 1 watt on the protect board.
 
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one board down, all transistors changed and .5 ohm resistor. Q8 and Q9 go in backwards as the board shows bce and they are ecb, as do the others. I will tackle the AWM-025C this weekend.
 

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Ok , the AWM-025C is complete with all new transistors, and diode installed. Q10,Q11 on AWH023 go printing facing up . Now to build me a DBT. I have double checked my work, now lets see if its correct. Here's to hoping.......
 

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Have to go to store for a bulb, so tomorrow.

but in the mean time , the manual stated to adjust VR3 for voltage reading of 25mV between terminals 9 and 13. I want to make sure I do this right... So positive on my meter to 9 and neg to 13. I see on the schematic that they should read +11mv and -11mv each....is that referenced to ground?
 
So on the power amp assy board i get the following readings AWH023

Pin 1 23.69v Manual 24 V
Pin 6 -41.33v Manual -42v
Pin 8 41.37v Manual 42V
Pin 9 15.76V Manual 11MV
Pin 11 -45.83V Manual -45V
Pin 13 15.68V Manual -11MV

So Pin 9 and 13 are way off and pin 13 is positive?

Also redings on the AWM-025C

Pin 1 15.72 V
Pin 3 0.001 V
Pin 5 15.69v
Pin 6 15.68V
Pin 7 10 MV
Pin8 -5MV


Pin 2 -12.8v Manual -13V
Pin 12 7.5V AC Manual 7.5V AC
Pin 11 33.8V Manual 35V
 
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I am going to check everything on the power board. power coming in is fine so back to the drawing board
 
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