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Need Sony Help

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bluvet79

New Member
Hi I have been working on my sony sa-wmsp1 powered subwoofer for over a month now and I can't seem to find the problem. It has power but no sound. I have replaced the amp. # LM3886TF and still no good. Can you guys take a look at my Schematics and see what you can find and advise me Please.

Thanks;
Gary
View attachment schematics.pdf
 

Nigel Goodwin

Super Moderator
Most Helpful Member
It's a simple enough unit (although I couldn't read the PDF you posted), for a start have you checked the speaker? - it may be O/C.

Second, check the voltages on pins 1, 3 and 4 of the chip.

Third, does the relay click a few seconds after you turn it ON?.
 

audioguru

Well-Known Member
Most Helpful Member
Pin 4 of the IC is its negative power supply pin. Since there is no voltage there then the wiring or bridge rectifier is blown.
 

bluvet79

New Member
audioguru said:
Ask an electronic technician to fix it for you.
You know I would do that but then what would I have learned other than someone else fixed it. I would like the knowledge for self experince. Now I changed out the rectifier bridge D401 and that made no change.

If you guys could assist me with tracing out the circuit it would be greatly appriciated.

Thanks;
Gary
 

audioguru

Well-Known Member
Most Helpful Member
Is there about -40V at the negative output terminal of the bridge rectifier?
If there is then follow it until it stops and you will find the problem. It looks like it goes through two connectors which might be loose.
 

bluvet79

New Member
Ok guys I have traced out the schematic and found that R401 and R402 are both getting the correct voltage in but are only putting out 3 volts also they are getting hotter than a firecracker. I also found that C101 is popped I even removed it to check it and still no continuity.
So what do you think.
 

audioguru

Well-Known Member
Most Helpful Member
The amp has many problems.
Capacitors are not supposed to have continuity.
 

audioguru

Well-Known Member
Most Helpful Member
Problems:
1) -40V is not getting to the amp IC.
2) The input capacitor popped.
3) The plus and minus 15V sources are overloaded by something.
 

bluvet79

New Member
Thank you for all of your help. I replaced the two resistors and the capacitor and the amp works fine now. This was a great learning experience and now I have the knowledge of tracing out this system.

Thank You;
Gary
 

anybody

New Member
what resistors and capacitor did you change? im in the same situation. i know its an old thread but maybe someone can help...
 
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