Pioneer SX-850 No Relay Click no sound

NICKAVIVA1

AK Member
Hello, Need some help here. I have this 850 that powers up and used to work, then suddenly started popping and cracking at any volume very badly, and then
once in a while on power up the relay will click on after about a 15-25 second delay. but now
last couple times I powered it up I get no relay click and of course no sound.
can someone be so kind as to walk me through some troubleshooting and testing
I have tried headphones and nothing. I do have Multimeter and do have limited
testing skills. ( I just noticed the pre-power amp jumpers are missing as well )
I do have some jumpers somewhere from an old pioneer. I did deoxit the controls
several times about a year ago and was working well. any help with Instructions
to test and measure will be greatly appreciated. I work in Bensenville Illinois
and cant find anyone who can look at this local.
Thanks
 
First get the Service Manual

http://www.kallhovde.com/pioneer/sx-850-sm.pdf

Get familiar with the power supply board schematic.

Do a thorough visual check for any weirdness on the boards in the bottom of the set.

Check all the fuses by removing them and checking for continuity.

If OK:

Power up the set.

Take DC voltage readings on pins 1 through 15, 17 and 18, and report your findings.
Note: Pins 1 and 12 are grounds (no voltage) but check for continuity to chassis.

A nicely laid out PS board with AC on one side (Pins 16 through 28. (17 and 18 are DC)) and DC on the other (Pins 1 through 15).

It looks like there is a few different PS Boards. Make sure the one you have matches the schematic.

Insulate the DMM Red probe up to the very point. This will help keep the shorts to a minimum (NO SHORTS :yes:). Black on a chassis ground.
 
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Hello Zebulon1, below are my readings as requested. since I had the time I also measured
the AWM-062 Protection boars as well.
Power supply board pins 2-15
Pin2- 5.3
Pin3 5.3
Pin 4 13.6
Pin 5 13.6
Pin 6 51.7
Pin 7 51.7
Pin 8 37.1
Pin 9 37.1
Pin 10 37.1
Pin 11 28.8
Pin 13 13.1
Pin 14 51.5
Pin 15 23.2
Pin 17 46.4
Pin 18 46.4
Protection Board Readings
Pin 1 0
Pin 2 13.1
Pin 3 2.4
Pin 4 0v
Pin 5 0
Pin 6 0
Pin 7 2.6
Pin 8 2.4
Pin 9 37.2
Pin 10 37.2
Pin 11 37.2

I hope this helps
Thanks
 
Geez, now I know of two people who live in Bensenville.....
 
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Have you figured it out yet?

Good job on the readings. Protection voltages where the key to your issues!

Good news: The power Supply is spot on.

Bad news: Left channel of the Amplifier is not putting out any voltage.

This is a old post from MTF. Most of the transistors are still available but under a different prefix.

More than likely the 2SA726's, Q1 and Q3 went bad. They are known for this issue.

--- differential inputs
*** you need to get a bunch and match Q1 & Q3 hfe's for best performance on bias circuit***
Q1 2sa726 to-92 bce 50v .1a .12w 100mhz 500hfe >>> KSA992
Q3 2sa726 to-92 bce 50v .1a .12w 100mhz 500hfe >>> KSA992

*** 08-22-2014 Edit: need equivalents.****
Q5 2sa818 case? ebc 180v .05a 1w 100mhz 70-240hfe >>> KSA910
Q7 2sc1628 case? ebc 160v .05a 1w 120mhz 70-240hfe >>> KSC2310

--- drivers
Q9 2sd381 to-220 bce 120v 1.5a 20w 40mhz 40-250hfe >>> KSC2073
Q11 2sb536 to-220 bce 120v 1.5a 20w 40mhz 40-250hfe >>> KSA940
--- outputs
Q13 2sd271 npn to-3 xxx 160v 6a 50w 5mhz 40-240hfe >>> MJ21194
Q15 2sb531 pnp to-3 xxx 160v 6a 50w 5mhz 40-240hfe >>> MJ21193
 
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Hello Zebulon1, below are my readings as requested. since I had the time I also measured
the AWM-062 Protection boars as well.
Power supply board pins 2-15
Pin2- 5.3
Pin3 5.3
Pin 4 13.6
Pin 5 13.6
Pin 6 51.7
Pin 7 51.7
Pin 8 37.1
Pin 9 37.1
Pin 10 37.1
Pin 11 28.8
Pin 13 13.1
Pin 14 51.5
Pin 15 23.2
Pin 17 46.4
Pin 18 46.4
Protection Board Readings
Pin 1 0
Pin 2 13.1
Pin 3 2.4
Pin 4 0v
Pin 5 0
Pin 6 0
Pin 7 2.6
Pin 8 2.4
Pin 9 37.2
Pin 10 37.2
Pin 11 37.2

I hope this helps
Thanks
problem is pin 3 protect board .it should read 0v . same as pin 1 .
its probably the diff pair at fault q2 and q4 .
you could try adjusting vr12 and see if you can get the voltage down near 0v at pin 3 protect board
 
Thanks Pete! I got it backwards.

"NicK" I can gain match the 992's if you need that done.
 
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If you are going to get the soldering iron out you might as well rebuild the entire power amp, both sides, while you are in there rebuild the remaining boards, it will last you another 40 years.

Zeb, I use KSA1381 for Q5 & Q6 and KSC3503 for Q7 & Q8 on the power amps.
 
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Thanks to all of you, I am a first timer at the repair end. I am going to need some
step by step Instructions, if anyone would be so kind. so the protect board is the
main issue correct?
thanks
 
Also, how do I get the protect out enough to get to the back side? it seems something
is hanging it up in the center area after I loosen the white posts.
any help is appreciated
thanks again
 
The amplifier board is the problem.
The 2sa726's Q1 through Q4 are most likely the culprits.
The list above with help from tsd71 is the complete tranny list for the board. The replacement transistors for the 2SA726's are the KSA992's and good practice is to gain match them before installing.
How confident are you in working on the amp board?
 
not to confident, but also not afraid of a challenge. I would love to have someone
Rebuild all the problem boards, but not really anyone around here that I know of.
My solder skills are very rusty . I guess just knowing the in and outs of getting the the
Board pulled out enough to get to the solder and all, hate to cause more damage.
 
Well, here's the list for the amp board.
Will the members check on the Bourns trimmers I selected. I always have a hard time finding the ones I want.

Power Amp Board (AWH-059)

AWH-059: C1: 2.2uF 25v CSSA: 647-UKL1H2R2KDDANA 2.2uF 50v
AWH-059: C2: 2.2uF 25v CSSA: 647-UKL1H2R2KDDANA 2.2uF 50v
AWH-059: C3: 1uF 25v CSSA: 647-UKL1H010KDDANA 1uF 50v
AWH-059: C4: 1uF 25v CSSA: 647-UKL1H010KDDANA 1uF 50v
AWH-059: C5: 33uF 16v CEA: 647-UPW1C330MDD 33uF 16v
AWH-059: C6: 33uF 16v CEA: 647-UPW1C330MDD 33uF 16v
AWH-059: C11: 330uF 10v CEA: 647-UPW1A331MPD 330uF 10v
AWH-059: C12: 330uF 10v CEA: 647-UPW1A331MPD 330uF 10v

VR1: 10K ohm - 652-3266P-103LF-ND
VR2: 10K ohm - 652-3266P-103LF-ND
VR3: 100 ohm - 652-3386H-101LF-ND
VR4: 100 ohm - 652-3386H-101LF-ND

(For best results: Gain match the paired 992's)
AWH-059: Q1: 2SA726: 512-KSA992FBU
AWH-059: Q2: 2SA726: 512-KSA992FBU
AWH-059: Q3: 2SA726: 512-KSA992FBU
AWH-059: Q4: 2SA726: 512-KSA992FBU
AWH-059: Q5: 2SA818: 512-KSA1381ESTU
AWH-059: Q6: 2SA818: 512-KSA1381ESTU
AWH-059: Q7: 2SC1628: 512-KSC3503DS
AWH-059: Q8: 2SC1628 512-KSC3503DS
AWH-059: Q9: 2SD381: 512-KSC2073H2TU
AWH-059: Q10: 2SD381: 512-KSC2073H2TU
AWH-059: Q11: 2SB536: 512-KSA940TU
AWH-059: Q12: 2SB536: 512-KSA940TU

OUTPUTS PNP: MJ21193G (4 EACH)
OUTPUTS NPN: MJ21194G (4 EACH)
 
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If you wanted to do the quick and dirty. Just replace the 2SA726's. There would be a few procedures to comply with before you can say its fixed. Not to awful hard. Build a DBT. Tickle the Dragons Tail. Fun stuff!
 
Zeb, Maybe the quick and dirty would be a great start for me, can you get me going?
I do appreciate all of everyones help here.
thanks
 
Will the members check on the Bourns trimmers as selected. I always have a hard time finding the ones I want.

AWH-059: VR1: 10K OHM: 652-3309W-1-103 ?
AWH-059: VR2: 10K OHM: 652-3309W-1-103 ?
AWH-059: VR3: 100 OHM: 652-3309W-1-101 ?
AWH-059: VR4: 100 OHM: 652-3309W-1-101 ?

Zeb, I don't have enough experience to know if those will work or not, but I just finished up one of my 850's last week, and this is what Mark suggested:
VR1: 10K ohm - 652-3266P-103LF-ND
VR2: 10K ohm - 652-3266P-103LF-ND
VR3: 100 ohm - 652-3386H-101LF-ND
VR4: 100 ohm - 652-3386H-101LF-ND

(652-3386H-1-101LF VR3 bias 100 ohm 1 turn
652-3266P-1-103LF VR1 offset 10k 12 turn)

They worked great for me. The leads were on the shorter side, but maybe that's the way trimmer pots come? Anyway, the important point is that I was able to dial everything right in. :thmbsp:

Jeff
 
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