Im sorry there is no U104 and that picture is not the board I have. The board number I have is PC-2565-D That board layout looks totally different.
Note to self...
For future reference, use h13602_schematic.pdf.
If you don't have signal out of U201, touch the RCA center conductors of one of the RCA plugs (leave the other one plugged into the left channel) to R201. Does that make the right channel produce audio?
For future reference, use h13602_schematic.pdf.
If you don't have signal out of U201, touch the RCA center conductors of one of the RCA plugs (leave the other one plugged into the left channel) to R201. Does that make the right channel produce audio?
No I cant get it to produce audio doing that, even clipped a bananna plug to the center of the rca plug and touched a bare wire to R201 both sides and nothing.
Are all of the pins on thie op-amp very near 0v except for the power supply pins (which should be at ~±15v)?
If you are refering to U201 yes all the pins are near zero except the supply pins. The highest reading was 0.080 vdc.
Pin4 -13.48 vdc
Pin8 +14.38 vdc
Pin4 -13.48 vdc
Pin8 +14.38 vdc
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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.
OK here is what I found Perry.
Touching the center conductor of the RCA to R201 I have audio signal on one side of C202 but not the other. I still have no signal on pins 1 and 7 of U201.
Touching the center conductor of the RCA to R201 I have audio signal on one side of C202 but not the other. I still have no signal on pins 1 and 7 of U201.
C202 is either defective or something is loading the output side of the cap. What's the resistance from the dead side of the cap to the RCA shield?
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??
If all of the pins other than the power supply pins have 0v DC, it's likely OK but if you can change it easily, change it.
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.
Amp plays very clean, very loud audio both channels. It is running hard as we speak and sounds amazing. I cant believe the power this little amp puts to my test mids........WOW......think I will keep this one.
As always thank-you for all your help......most people probably would have given up on me with this one. I appreciate all your help and patience.
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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