SX-950 In Protection ... maybe more issues SOLVED

Johnny_Law

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PROTECTION ISSUE SOLVED! NOTE TO EVERYONE: PAY ATTENTION TO YOUR REPLACEMENT TRANSISTORS! AN NPN TRANSISTOR WON'T WORK IN A PNP SPOT! THANKS TO @petehall347 !

Picked up an SX-950 which was guaranteed, in person, to my face, to work great. Pretty excited, my first 'big' Pioneer. Of course, it does not work at all. o_O

First observation was that it was not coming out of protection. Other observations are that none of the speaker lights ever light up (A/B/C), and also that the source lights (Phono / FM / AM / Aux / etc) light briefly and quickly fade away.

I saw weird protection circuit readings. So, I replaced all caps & transistors in my power supply and my protection circuits. What did I use for replacements? Well, I followed the parts lists that are posted around here. I am (pretty) sure that all my transistor B/C/E and capacitor +/- orientations are correct. Will be confirming.

Unfortunately, I am getting wonky readings from my power supply, and wanted to post here for help / commentary as I go about scratching my head about it.

So here are the power supply (AWR-101) readings I have done so far:

R1, R2, and R20 all test OK

D1, D2, D3, D4 all test OK

Fuses all test OK

Outputs
Pins: Pin / Ref / Read
6, 7 51.5V 14.75V BAD
8, 9, 10 36.5V 10V BAD
11 28V 6.5V BAD
13 -13.5V -13.3V OK
14 -51.5V -51.5V OK
15 -19V -19V OK
4, 5 13.9V 2.8V BAD
2, 3 5.4V ?Oscillates? VERY BAD

Transistors:
Pins: B C E
Q1 15V 66.9V 14.4V WRONG B & E
Q2 -52.1V -67.2V -51.6V OK
Q7 6.8V 7.2V 6V ALL WRONG
Q3 4V 15.2V 3.4V ALL WRONG

Really, I'm confused as to HOW I can be getting such a bad reading at the Base of Q1 with R1 & R2 testing properly as well as D1-D4.
 
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Can you please post power supply and protection board readings. Also what did you replace on both boards. Q5 is a big issue on the power supply.
 
Can you please post power supply and protection board readings. Also what did you replace on both boards. Q5 is a big issue on the power supply.

(Most) power supply board readings are posted above. I'll post the protection board tonight.

I replaced all transistors and electrolytic caps on both boards. I used the recommended KSC2690AYS for Q5 on the power supply (and one for Q5 on the protection board too).

check D11 14v zener

Thanks - will do tonight.
 
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Congrats on the find! :)

Just threw my SX-4gs back on the stands on the 12th. ;)

can you believe they sound better than my BW 686's...

Kind Regards,
John
 
Thanks John - awesome! Glad to hear from you.

check D11 14v zener

Looks like you're right on the money. It appears to be shorted - I'm getting different readings forwards and backwards, but readings nonetheless (0.18V one way, 0.27V the other). I'm seeing the recommended replacement is 512-1N5244B from Mouser.

And for reference, the readings from the protection board are:

AWM-062
Pin / Ref / Read
2 -13.5V -13.2V OK
11 36.5V 10.1V BAD
12 7.5V 7.7V OK

Also I might as well mention an irregularity on the power supply board. There was a 47uF / 25V cap installed at C14 which according to the manual is 220uF / 10V, and I used a 220/16 (UPW1C221MPD).
 
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47uf is more used in the 850 and 950 than the 220uf. While your at it change the other diode on the PS board D12 or(ZD 2) use a 1N5243B
 
The best I could do locally was a couple NTE5022A zener diodes, 13V 1/2watt. I replaced zD1 and zD2 with them.

Now I am getting MUCH better readings but nothing dead on. ... And still in protection.

BUT the source & speaker lights now come on. However they get weaker when more lights come on. For example, the FM light is bright with no speakers selected. Then when I push speaker A, the speaker A light comes on and the FM light gets weaker. Confused about this, but since the lights actually work with the diodes replaced, it must be related ... somehow. ???

Anyway here are the pins of the power supply (AWR-101):

Pin / Ref / Pre Diode / POST DIODE
6, 7 / 51.5V / 14.75V / 45.3V MUCH CLOSER
8, 9, 10 / 36.5V / 10V / 32.6V MUCH CLOSER
11 / 28V / 6.5V / 24.9V CLOSE
13 / -13.5V / -13.3V / -12.9V FARTHER BUT STILL CLOSE
14 / -51.5V / -51.5V / -50.2V FARTHER BUT STILL CLOSE
15 / -19V / -19V / -18.8V FARTHER BUT STILL CLOSE
4, 5 / 13.9V / 2.8V / 12.2V MUCH CLOSER
2, 3 / 5.4V / Oscillates / 5.7V MUCH CLOSER

And the specific transistor pins of AWR-101:

(B C E)

PRE DIODE
Q1 15V 66.9V 14.4V
Q2 -52.1V -67.2V -51.6V
Q7 6.8V 7.2V 6V
Q3 4V 15.2V 3.4V

POST DIODE

REF 52.1V 60.7V 51.5V
Q1 46.1V 66.1V 45.6V CLOSER B AND E
REF -52.6V -62.8V -51.5V
Q2 -51V -67.2V -50.4V ABOUT THE SAME, STILL CLOSE
REF 28.7V 35.2V 28V
Q7 25.7V 31.6V 25.1V MUCH BETTER, CLOSE NOW
REF 15.2V 52.1V 14.6V
Q3 13.3V 46.2V 12.8V MUCH BETTER, CLOSE NOW

And the pins of the AWM-062 protection board:

AWM-062 REF READ POST DIODE
2 -13.5V -13.2V -13.0V
11 36.5V 10.1V 32.7V MUCH BETTER TO THE RELAY! BUT STILL NOT DISENGAGING!
12 7.5VAC 7.7VAC 7.7VAC
 
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Make sure all the grounds are making good connections. I remember a few years ago with strange problems on a tape deck. There was a screw that mounted the board thru one of the ground traces. Installed a "tooth" washer, replaced the screw, problem solved.

Reminds me of automotive, if there's an insufficient ground the lights will work until you want to light several at one time, then you can get strange happenings. Easy to check.
 
I'd check the remaining pins on the protection assembly to see if there is some condition that is keeping it in protection. If those pins look normal, measure protection Q6 and Q7 and follow the advice from MTF in the following post:

http://audiokarma.org/forums/index.php?threads/sx-950-protection-issue.776253/#post-10645656

Les

Thanks! Your point about pins 9, 10, and 11 on the protection board is that pin 9 will measure the same as pins 10 and 11 when in protection, since no current flows through the relay coil. This is the case here. Pins 9, 10, and 11 on my protection board all measure around 32V.

I measured R28 as well, which is a good ~218ohms.

Then as Mark suggested I shorted Q7 C to E and VOILA. Comes out of protection. Q7 is a brand new KSC2690AYS - I replaced with another new KSC2690AYS just in case - same result.

So now I'm kinda lost because the other transistors and the caps are new.

Make sure all the grounds are making good connections. I remember a few years ago with strange problems on a tape deck. There was a screw that mounted the board thru one of the ground traces. Installed a "tooth" washer, replaced the screw, problem solved.

Reminds me of automotive, if there's an insufficient ground the lights will work until you want to light several at one time, then you can get strange happenings. Easy to check.

Good point, or what your alternator starts to go. I can't find anything obvious but will keep looking.
 
Mark's test proves that your protection relay coil and R28 are both good. Could you also check the voltage on Pins 1, 3, 5&6 and 7&8 to see if there is an abnormal condition that's keeping it in protection? You should see only a small DC voltage here (bias and offset).

Les
 
In my experience with the 950 there are times when I had these issues,it could be a multitude of things, but here are two you should look at right now. Reflow the solder on all the protection board pins from the bottom of the board. Also make sure all the diodes on that board are not open,they all can be easily replaced with 1N4148, except D8 next to pin 12 use a 1N4004
 
I'd like to start over if tsd's suggestion doesn't help.
Could you give all the protection boards pin readings again? Mabe you did already but I want to see them now. Currently.
I saw the post where the protection PS voltages were posted.
Looking to see pins:
Pins 1, 3, 5, 6, 7, and 8. These are the amp readings the protection needs to see correctly. Readings in DCmV's.
With:
Set on, volume min, jumpers pulled.
 
Thought they were posted but defiantly post those and power supply measurements again..After the addition of new components
 
I re-flowed each pin on the protection board, checked all diodes (all are OK), pulled the jumpers, and measured the protection board's pins per @LesE and @zebulon1 :

1. 0.44V
2. -10.2mV BAD
3. 0.44V
4. 0V - 0.3mV (fluctuating)
5. 0.44V
6. 0.45V
7. 0.44V
8. 0.43V
9. 32.7V
10. 32.7V
11. 32.7V
12. 7.5VAC

Then I noticed that the wire from pin 2 of the protection board to pin 13 of the power supply board was no longer making good contact.

So I went to measure the voltage at pin 13 of the power supply, looking for the -13.5V, but my fat fingers caused pins 13 and 14 to bridge. POOF fuses 25 and 26 blew and now I am going to trace that circuit on the power supply to see if I blew anything else.
 
get the supply fixed then check voltages across each output transistor emitter resistor r55 etc .
if they are about right you could lift r9 r10 on the protect board and get pins 1 and 3 voltages again .
i have seen q1 q2 bad on the protect board in the past . pulling those resistors should reveal something .
 
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Protect Pins 1, 3, 5, 6, 7, and 8 should be darn near zero. Half a volt is too much.
 
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