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amp- no sound

hello.

I am trying to fix this old amp which was lieing at a friends house and produces no sound.my knowledge in electronics is minimum so this is what i did so far:

  1. looked at the board, and so there is no burned(black) particles
  2. tried to track down an input singal while the amp is off

results:

  1. there are no "black" paritcles, but there are some yelloish orange stains which lie betwean few ressistors and such (u can see it from the other side of the board)

  1. the sginal splits in many places and i got lost a bit, so i just tried to c if it makes it to the ic (stk2230) and it does. the problem was when i tried to turn the amp back on and i touched the ic pins with my multimeter it sparked, but i m not sure it ruined the thing, i think i just touch a high voltage pin.

my question:

i understand the best thing to do is to get the schematics and see which voltages i am expecting at different places on the amp and check it. the only thing is i am afraid of doing thisbecause of the sparks i got touching the stk2230(not just sparks there is now also a little black stain near the leg i touched(

so, what is the right way to do this? did i get the aprk cause my multimeter was set on 200 V max AC?

TIA

Eyal

Reply to
eyal
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What kind of amp are we talking about? Home stereo, PA, what brand/model?

Reply to
Mike W.

Luxman Lv-90

its a home stereo one

Reply to
eyal

Reply to
JFETR

it is pin #5.

so, is scope absolutly nessery here? can't i make my way with a multimeter?

what about them yellowish orange stains on the bord (close to solderings), how should i take care of them if at all?

Reply to
eyal

For audio testing one of the easiest ways is with a signal tracer. Basically a tone generator and separate amplifier. You feed the tone generator into the input, and use the amp on the output of each stage until you find the one where it disappears.

--
*It's lonely at the top, but you eat better.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.
Reply to
Dave Plowman (News)

Reply to
JFETR

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