OK. Touch the center conductor to the resistor again and look for signal on both sides of C202 as well as on pin 1 and 7 of U201. Touch the scope to the resistor/center conductor of the signal line to let you confirm that you have signal and so you'll know what to look for on the points listed above.
I replaced the cap and still the same result. No audio.
BUT.....I slipped when testing pin 7 on the op-amp and shorted pins 7 and 8 together and the speaker made a loud pop. Then it produced low audio, could barely hear it. If I short pins 7 and 8 together with a wire the audio gets considerably louder but is still not at full output.
Thoughts on that?? Maybe a bad op-amp??? I have several 100 TL072 maybe I should change it and see what happens??
BUT.....I slipped when testing pin 7 on the op-amp and shorted pins 7 and 8 together and the speaker made a loud pop. Then it produced low audio, could barely hear it. If I short pins 7 and 8 together with a wire the audio gets considerably louder but is still not at full output.
Thoughts on that?? Maybe a bad op-amp??? I have several 100 TL072 maybe I should change it and see what happens??
Perry changed out U201 and the amp produces audio at full power with a sine wave. Wave form looks good on scope as well. Maybe the op-amp was fine but due to the other components failing it got hot and broke the leg loose from the solder pad??? I am gonna grease it put it in sink and run it hard. I will post results.
This kinda reminds me of the 400a4 you helped me with that had risitor that tested good but was bad.
This kinda reminds me of the 400a4 you helped me with that had risitor that tested good but was bad.
This kinda reminds me of the 400a4 you helped me with that had risitor that tested good but was bad.
Sometimes you have to narrow the problem down to one or two components and then replace them if you can't determine which one is at fault.
Did you measure the DC on the terminals of the op-amp before replacing it?
Yes I did they were all near or at 0.000 vdc the highest being 0.080 vdc except for the supply pins which were at proper voltage. Not sure why it measured good or why shorting pins 7 and 8 made the channel have partial sound. Soon as I changed it, the amp worked awesome. Go figure huh?
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