SOLVED Angry Andy Plus Drive problem

[SteveScott]

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.

 

[SteveScott]

Check your Voltages again but put the Black probe to Ground on Input Jack.

Will do, but that's going have to wait until I get home from work tonight. So hopefully we can pick up in the morning. Thanks.

 

[SteveScott]

Check your Voltages again but put the Black probe to Ground on Input Jack.

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

 

[SteveScott]

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

Correction, input jack. I don't think it should matter, but just wanted to be as accurate as possible.

 

[music6000]

Have you tried another Op Amp ie: JRC4558, TL072

 

[SteveScott]

Have you tried another Op Amp ie: JRC4558, TL072

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.

 

[Chuck D. Bones]

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.

 

[SteveScott]

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.

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.

 

[Chuck D. Bones]

Right, I meant to type the 15th.

 

[SteveScott]

2 new items by Steven Scott

photos.app.goo.gl

All cleaned up. I check the resistance between pin 1 and ground prior to cleaning. It showed 20K with the drive down and 128K with drive up. And the voltages were unchanged prior to cleaning. I have not checked anything after cleaning yet, next on my list.

 

[SteveScott]

Everything measures the same even after the alcohol cleaning.

 

[Chuck D. Bones]

Just be clear, the IC was out of the socket when you made those measurements, right?

 

[SteveScott]

The ic was out for the resistance readings, in for the voltage.

 

[Chuck D. Bones]

The ic was out for the resistance readings, in for the voltage.

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?

 

[SteveScott]

I just replaced C4. All good! Thank you.

 

[Chuck D. Bones]

Yay!