Special Overdrive Troubleshoot Help Needed!

[HGWHatchQ]

Good Morning all!

I recently completed the SOD PCB and have completed the wiring. My problem is this... The bypass works but when the effect is on we get nothing! We used an audio probe and have traced the signal loss to the Q1 transistor. We have a signal to the center pin BC548B but nothing out the other pins. I have tested several other transistors to make sure its not bad/damaged but im at a loss atm. Any ideas/help would be amazing!

 

[Chuck D. Bones]

Solder joints look ok. The parts I checked visually look like the right ones, pointed the right way. Except IC1, you subbed TL072 for OPA2134. Should still work. I can't see R17, C9 is blocking the view. I was gonna ask if the LED on the front panel lights up, but it looks like you haven't installed it yet. With power on and no input, measure the DC voltage on each side of R4 w.r.t. ground. The bottom side should be +4.5V, the top side a little less. If those check out, measure Q1 pin 3 (emitter). Should be around +3.9V. If those do not check out, measure the DC voltage on Q3-1 (collector), should be +9V. If it's zero volts, then power is not getting to the board. The power connector has 3 terminals and you might not be connected to the right ones.

 

[HGWHatchQ]

Awesome! ill do the checks you suggested and will get back with the info asap! Thank you Sir!

 

[Nostradoomus]

Have you got a better picture of your switch wiring?

 

[HGWHatchQ]

Evening! Sry it took me awhile to get back home to conquer this issue! I’m pleased to report that after looking over the wiring for the power jack as Mr Bones suggested at the end of his reply. I inadvertently had the positive wired to the incorrect lug! It came to life but I had to touch up some joints to get the noise and scratch to go away!

 

[Chuck D. Bones]

Sweet!