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.

 

[mralanmorgan]

I've replaced the TL072 and those readings seem reasonable. The JCR4558 is hard to get a read on as they fluctuate. I assume that's due to the nature of the effect.

 

[Robert]

If the LED inside the heat shrink is pulsing with a fair amount of light you can ignore the 4558 for now, that's the LFO and it seems to be doing it's job.

Are the rate and brightness of the LED affected by the Speed/Depth controls?

 

[mralanmorgan]

If the LED inside the heat shrink is pulsing with a fair amount of light you can ignore the 4558 for now, that's the LFO and it seems to be doing it's job.

Are the rate and brightness of the LED affected by the Speed/Depth controls?

Yeah, the rate and depth seem to be working fine.

 

[Robert]

Double check those measurements on pins 2 and 3.

I believe you should have around 4.5V on those as well.

 

[Robert]

Are you numbering the pins in this order?

 

[mralanmorgan]

Are you numbering the pins in this order?

Nope, I went 1-5 2-6 3-7 4-8. Let me get another read.

 

[mralanmorgan]

Double check those measurements on pins 2 and 3.

I believe you should have around 4.5V on those as well.

Pin 2 is 0.15 and 3 is 0.34. Any idea where that discrepancy could come from?

 

[Robert]

Pull the IC out of the socket and measure again on the empty socket.

While you have it out check for continuity between pins 3 and 5 (with no power applied).

 

[mralanmorgan]

Pull the IC out of the socket and measure again on the empty socket.

While you have it out check for continuity between pins 3 and 5 (with no power applied).

I've got continuity with pins 3 and 5 based on your diagram above. With the chip removed it reads 1: 0.00 2: 0.00 3: 0.26 4: 0.00 5: 0.26 6: 0.00 7: 0.00 8: 8.85

 

[Robert]

Measure the voltage on each end of this resistor.

 

[mralanmorgan]

Measure the voltage on each end of this resistor.

View attachment 43551

With chip in or out?

 

[Robert]

Out for now.

 

[mralanmorgan]

Out for now.

0.26

 

[Robert]

On both ends?

 

[mralanmorgan]

On both ends?

I guess I don't understand. I put my dmm on V and put black to one side and red to the other...

 

[Robert]

Put the black lead on ground (the metal sleeve of one of your jacks) and the red on the left end of the resistor.

Notate the reading, then do the same thing for the right end of the resistor.

 

[mralanmorgan]

Put the black lead on ground (the metal sleeve of one of your jacks) and the red on the left end of the resistor.

Notate the reading, then do the same thing for the right end of the resistor.

I apologize Robert. Left lead is 0.25 and right is 8.85

 

[Robert]

OK, remove power and check for continuity between the left end and ground.

 

[mralanmorgan]

OK, remove power and check for continuity between the left end and ground.

No continuity.