Build Your Own Clone Message Board

I built the FET Preamp around 8-10 years ago. It stopped working randomly, so I’ve been searching here to figure out how to troubleshoot it. I am powering it using a new 9V battery. When engaging the footswitch, the LED lights up, though sometimes it flickers randomly as if there’s a loose connection. Initially when it first stopped working, there would be no sound output with the pedal engaged, normal signal when bypassed. If I max out the volume knob when engaged, I can hear a very subtle signal come through my amp. I opened it up, and from what I can tell, there are no visibly faulty solder joints or obvious component failures.

I got the multimeter out and started checking voltages across the ICs like many other threads recommended (all the while, I had my guitar plugged in and would keep a few strings ringing out of curiosity in case it started working). The signal started coming through while messing with the pedal and would go in and out randomly. It seemed like there was a loose connection somewhere or something being ground out, yet I can gently shake the pedal when it’s working and it doesn’t seem to have an affect on the signal. I did notice that when it would go out again, I could strum my guitar fairly hard and it would push that hard attack of the signal through but immediately cut out again. This was repeatable while messing with it tonight.

Any idea what this could be?

Voltage readings across ICs:
IC1
1. 4.68
2. 0.00
3. 4.68
4. 0.00
5. 1.30
6. 4.59
7. 4.58
8. 9.29

IC2
1. 4.60
2. 0.00
3. 4.60
4. 0.00
5. 1.32
6. 4.59
7. 4.57
8. 9.28

When a pedal works for a while and then stops working, it's usually a solder joint that has broken or a wire that has come loose. In either case, the solution is usually to reflow all the solder joints in the build. If the LED is flickering, that suggests that perhaps the problem is at the DC jack or ground. I would start there, but it doesn't take too long to reflow the whole build.

If you post some photos of the build (especially the solder side of the PCB and your wiring), we can take a look and let you know if we see anything specific.

_________________
Scott

My band, Austin Hollow

Thanks for the info, Scott. Now that I'm looking at it more this morning, there are a few joints that could use some love. Also, the plastic shell for the DC jack was broken at some point. Could that broken DC jack be a contributing factor even if it's not being used to power the pedal?

I don't see anything obvious, but based on your symptoms, I would say you definitely have a break somewhere. The only advice is to reflow everything. PCB. Jacks. Foot switch.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

The battery connection is made through the DC jack, so it's necessary even if you're not using a power adapter. You could see if you can reliably cause and solve the problem by messing with the jack and its wiring, but my guess is that if it's providing power sometimes, it is not damaged internally… and you're back at square one, which is the solder reflow.

_________________
Scott

My band, Austin Hollow

I finished the reflow a little bit ago and it seems to be working flawlessly again, and of course it sounds fantastic. I did mess up the DC jack even more when getting it back installed in the enclosure. I may just get a replacement for it at some point so I'm not dependent on batteries for it.

Thank you all for the help! Add yet another tick to the just reflow solder the whole thing win column!

Glad to hear it!

In situations like these, I usually recommend getting another kit immediately so you can ride the momentum.

_________________
Scott

My band, Austin Hollow

Ya know, I was actually thinking about it..