SOLVED Angry Andy Plus Drive problem

S

SteveScott

Member
I got this thing all together, the only thing not working is the drive pot. With it turned all the way down, everything else works as expected. When you turn up the drive even a little, all sound is lost. All three lugs of the pot ohm out correctly, it is a linear 100k pot. Can a pot be bad, even though the meter seems to indicate that it's OK? Or is there another angle I need to be looking at? Thanks for any help.
 
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music6000 said:
Check your Voltages again but put the Black probe to Ground on Input Jack.
Click to expand...
Here are the voltages as requested using the output jack ground.
Pin 1 4.81
Pin 2 4.43
Pin 3 4.06
Pin 5 4.185
Pin 6 4.185
Pin 7 3.94
Pin 8 8.35
Not much different. However it occurred to me that these readings are with the gain all the way down. I turn the gain all the way up. As I expected, pins 5 - 8 did not change. But pins 1 - 3 did. Here are those readings with the gain all the way up.
Pin 1 7.17
Pin 2 0.875
Pin 3 3.82
 
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SteveScott said:
Here are the voltages as requested using the output jack ground.
Pin 1 4.81
Pin 2 4.43
Pin 3 4.06
Pin 5 4.185
Pin 6 4.185
Pin 7 3.94
Pin 8 8.35
Not much different. However it occurred to me that these readings are with the gain all the way down. I turn the gain all the way up. As I expected, pins 5 - 8 did not change. But pins 1 - 3 did. Here are those readings with the gain all the way up.
Pin 1 7.17
Pin 2 0.875
Pin 3 3.82
Click to expand...
Correction, input jack. I don't think it should matter, but just wanted to be as accurate as possible.
 
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music6000 said:
Have you tried another Op Amp ie: JRC4558, TL072
Click to expand...
I did try two separate IC's, both the LM833 that is called for. I will try your suggestions tonight to see if that helps. I did start another one of these and I am not having the same issue, but am having an issue with the boost circuit making some squealing noises. I am going to try another transistor on that one and see if that fixes it. If not, I will start a new thread for that one so as to not confuse the two different builds with separate issues.
 
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The symptoms make me think there is DC a leakage path on the board.
Those last photos you posted on the 5th... the board still has way too much flux on it. Flood the board with alcohol and scrub with a toothbrush until all of the flux reside is gone. Don't let dirty alcohol get into the pots and contaminate them. Recheck the voltage on pin 1 with DRIVE all the way down and all the way up. If the voltage is not between 4V and 5V for both measurements, then power off, pull the IC out of the socket and measure the resistance from pin 1 to ground. Should read open-circuit no matter how DRIVE is set. Make sure your DMM is set for the highest resistance setting.
 
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Chuck D. Bones said:
The symptoms make me think there is DC a leakage path on the board.
Those last photos you posted on the 5th... the board still has way too much flux on it. Flood the board with alcohol and scrub with a toothbrush until all of the flux reside is gone. Don't let dirty alcohol get into the pots and contaminate them. Recheck the voltage on pin 1 with DRIVE all the way down and all the way up. If the voltage is not between 4V and 5V for both measurements, then power off, pull the IC out of the socket and measure the resistance from pin 1 to ground. Should read open-circuit no matter how DRIVE is set. Make sure your DMM is set for the highest resistance setting.
Click to expand...
Thanks, I did clean and repost pictures on the 15th, but I will clean with alcohol as per your recommendation. I will also follow your other advice tonight when I get home and report the results as soon as I can. I truly appreciate all the help.
 
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SteveScott said:
The ic was out for the resistance readings, in for the voltage.
Click to expand...
Then there is a current leakage path thru or near C4. Do some careful inspection around C4, R5, R6 & IC1. C4 may be bad. If visual inspection doesn't reveal anything, remove C4 and repeat the resistance measurement. You're not touching any solder joints with your fingers when you make the measurements, right?
 
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