Sx 980 not working, no ac reading from pin 1???

looks like the vol pot is possibly broken internally then . or there could be a problem with the loudness circuit .maybe the switch . try loudness on and see if it evens up .
 
looks like the vol pot is possibly broken internally then . or there could be a problem with the loudness circuit .maybe the switch . try loudness on and see if it evens up .
Goshieeeee..........I just make a big stupid mistake. While I measured the voltage of pin 1, accidently touch pin 2 togather. I hear a pop-spark sound. After that happening, I only got -0.20 vdc from pin2(used to get -51). Now Relay is not even clicking. Tried to repair uneven balance of sound and made worse..:eek:
Now what am I supposed to replace? all weekend time consuming repair efforts are gone for a stupod mistake...:(
 
hold one why are you measuring voltages ?
anyway what's done is done and needs fixing .what pins are you talking about ?
i wont see your reply until tomorrow its near 1am here
 
hold one why are you measuring voltages ?
anyway what's done is done and needs fixing .what pins are you talking about ?
i wont see your reply until tomorrow its near 1am here
I just went over everything all over again for repairing. It was Stupid try....they are pin 1 and 2 from awm 124 (relay board). After that happening, I checked all diodos using my multimeter and found mz130 (d9 diodos) on power supply board(awr165) get bad (possibly fried). All other diodos for boards seem fine. Does it make sense to you? Or that diodos is not related with this happening. Do I need check other things? Anyway thanks for your help and have good night.
 
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you need to check everything in the -50v supply .including q3 q4 and all resistors .
also check d11
Thanks for reply. I only had short time available today morning before work, so I had quick check for voltages on power supply board, q3, and q4. I will do resistors and diodos once I go back home today. I got these numbers so far

P10 71v
P9 13.16v
P8 30v
P2 -0.216V
P5 -30V
P1 19.8

FROM POWER SUPPLY BOARD
P22 51V
P23/24 24V
P25/26 0.72
P27 -0.1
P28 -0.75
P20 34.70

Q3 Q4 both showing up negative volage
Q3 -0.67/-0.67/-0.93
Q4 -0.19/-9.32/-0.53
I will give you test results for resistors tonight. I should have just left what i had yesterday. Made it worse. :(
Thanks for your help and I really appreciate what you do for me.
 
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. you need to pull the transistors out for testing .
Petehall, I have a dumb question. I want to make sure about test you mentioned earlier.
So, no b/c/e voltages READING for q3 and q4? I just need test for wheather they are fried transistors? That is why you ask me to pulling transistors for test? I HAVE read some forums about repairing SX980 and found some require for b/c/e voltages' numbers and some requires diode test for them. since I am a beginner here, alot of confusing going on....:)
 
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voltage testing obviously in circuit and if odd readings with no apparent other fault its pull the transistor out of circuit for testing on diode test or hfe test if you have that function on your meter .
 
voltage testing obviously in circuit and if odd readings with no apparent other fault its pull the transistor out of circuit for testing on diode test or hfe test if you have that function on your meter .
8076035d16597a9f6923f15838a6759d.jpg
 
you need to check everything in the -50v supply .including q3 q4 and all resistors .
also check d11
Finally I tested Q3, Q4, ALL resistors, and diodes
It turned out Q3 is bad.
Q4 still good

D11 is fine and D9 is bad

R1 10
R2 10
R3 6.9
R4 1.5k
R5 1.5k
R6 1.5k
R7 1.5k
R8 15 -------bad
R9 10
R10 9k -------bad
R11 2.7k
R12 15k
R13 6.2k
R14 5.6k
R15 15k
R16 910
R17 910
R18 160-----bad
R19 3.9k

Shold I go head order and install all bad resistors , Q3, and D9 diode? Thanks
 
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yes get them ordered .
Yes I ordered resistors, diodes, and Q3. Ended up with ordering all other transistors and diodes for power supply board in advanced since they are not expensive. 3 to 5 days to get them into my house. I will let you know once I install them. Thanks
 
yes get them ordered .
I got and installed all parts. It is on and working again although uneven volume issue still exist. Thanks for your kindly help. I guess I should look for new volume pot and replace old one. Or I can disassemble old volume pot and clean inside really hard. :)
 
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Opend volume control pot and found all contact coppers pretty worn up. Also no lubricate left in the pot. I think I need order a good used volume pot. :(
 
Petehall, You r right. The old volmune potentiometer was cause for problem. As soon as I replace with other used one and reassemble every parts again, unbalanced volume issue is gone now. It must be pretty bad inside of the pot althogh did not look like that bad. It is working strong and great. I love this SX980. More and more I listen, I get amazed for great performance of this amp. Thanks for your help again and sorry for begging you for help.
 
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