Moonshot Trem (no signal when engaged)

[mralanmorgan]

I thought this was a straightforward build, but here I am. Bypass works fine and all the LEDs work as they should (pulsing). I don't know where to start with troubleshooting.

 

[Robert]

Check the resistance of that resistor.

 

[mralanmorgan]

Check the resistance of that resistor.

I've got the dmm set on 200k and it's reading 47.0...think this might be the problem.

 

[Robert]

It depends on how your meter displays values in a particular range.

47.0 could mean 47K since you're in the 200K range.

Measure the 10K resistor two resistors above that one (below the 330pF capacitor) just for comparison.

 

[mralanmorgan]

It depends on how your meter displays values in a particular range.

47.0 could mean 47K since you're in the 200K range.

Measure the 10K resistor two resistors above that one (below the 330pF capacitor) just for comparison.

Same setting of 200k it's reading 9.6

 

[Robert]

OK so it just doesn't display the unit letter.

The low reading probably isn't a problem since you're measuring the resistor in-circuit.

 

[mralanmorgan]

Same setting of 200k it's reading 9.6

Changed it out with a resistor that read 99.8k. Still no signal.

 

[Robert]

I bet it measures around 47K now that it's installed in the circuit.

 

[mralanmorgan]

OK so it just doesn't display the unit letter.

The low reading probably isn't a problem since you're measuring the resistor in-circuit.

...oh, my bad. I got ahead of myself.

I bet it measures around 47K now that it's installed in the circuit.

I'm not surprised, you are correct.

 

[Robert]

OK, using the image above check the resistance of R102.

https://forum.pedalpcb.com/attachments/1678316132053-png.43556/

 

[mralanmorgan]

OK, using the image above check the resistance of R102.

https://forum.pedalpcb.com/attachments/1678316132053-png.43556/

47.3k

 

[Robert]

I'm stumped... Your 9V supply is dropping across R101 so there must be a short of some sort.

With the IC removed the only components on that line are R101, R102, and C101.

Unless C101 is defective there must be a solder bridge or other short underneath one of those components, or the IC socket itself.

 

[mralanmorgan]

I'm stumped... Your 9V supply is dropping across R101 so there must be a short of some sort.

With the IC removed the only components on that line are R101, R102, and C101.

Unless C101 is defective there must be a solder bridge or other short underneath one of those components, or the IC socket itself.

I'll check/replace c101...these sockets are about impossible to remove, huh?

 

[Robert]

It can be a little tricky, it's usually easier to just destroy the socket rather than try to salvage it.

Before you start pulling a bunch of components check for continuity between Pin 3 or 5 (they're connected together) and each other pin of the socket.

 

[mralanmorgan]

It can be a little tricky, it's usually easier to just destroy the socket rather than try to salvage it.

Before you start pulling a bunch of components check for continuity between Pin 3 or 5 (they're connected together) and each other pin of the socket.

Should only 3 and 5 have continuity?

 

[mralanmorgan]

Should only 3 and 5 have continuity?

Only 3 and 5 have continuity. No other pins have a connection. I replaced c101...I'll see if it works.

 

[mralanmorgan]

It can be a little tricky, it's usually easier to just destroy the socket rather than try to salvage it.

Before you start pulling a bunch of components check for continuity between Pin 3 or 5 (they're connected together) and each other pin of the socket.

I pulled both c101 and c5 (the strip had turned red indicating too much heat). There's only continuity on pins 3 and 5 on the tl072 socket. I've been staring at it all day and can't find any grounding issues...I've got another board, but I'm afraid to try it.

 

[Robert]

It's odd because at one point you measured 4.5V on one of the pins, and that's what we're trying to find.

 

[mralanmorgan]

It's odd because at one point you measured 4.5V on one of the pins, and that's what we're trying to find.

I was even able to get the socket out and replace it. I even went as far as putting a new chip in...bummer.

 

[mralanmorgan]

It's odd because at one point you measured 4.5V on one of the pins, and that's what we're trying to find.

Still not a clue as to what happened to this one, but I just boxed up the second board (Moonshot) and this one's working great. Thanks for your time and support, Robert.