Kliche Power Problem - Charge Pump/LED Oscillation

[ddavis20341]

I have a Kliche build that has been giving me some problems recently. It stopped working - passing either bypass or circuit audio - and the only sound is just a rhythmic pumping noise (it pumps in time with the LED on the power brick in the video below). I tried swapping the charge pump and DC jack, re-flowing joints, etc. and still no dice. As you can see, voltage jumps rhythmically, but is always between 0-0.5V. I checked continuity on ground between DC jack, input output jacks, etc. Could it be a bad filter cap? Confused as to what to try next.

https://imgur.com/JoZoABl

https://imgur.com/G45GAaK

https://imgur.com/RzxBVPF

https://imgur.com/xeRKSad

https://imgur.com/5PUbN5h

 

[Robert]

Pull out both TL072s, install a known good charge pump, then see if the voltage stabilizes.

 

[DailyDovetails]

I haven’t done this pedal and the board looks a little specific but when I have had issues like this before it has typically been an issue where the positive is shorted to ground. I would try checking the voltage on the power supply to make sure it’s 9 volt and then maybe pull the IC you think might be in faulty and see if you get 9 volt back inside the pedal, otherwise I would check where you are getting continuity to ground that you shouldn’t be.

Hopefully some of that helps if not there is tons of people on here more experienced that have probably built several of those.

 

[synthesiserror]

I don't know where you bought yours, but I've noticed that when I buy charge pumps from anywhere other than Digikey or Mouser, about 1 in 3 is bad. Maybe I just have terrible luck, but I think there are a lot of recycled chips on the market. Socket another one if you have one.

 

[ddavis20341]

I tried pulling the TL072s and trying 3 charge pumps (I didn't have any builds laying around that used a TC1044 to check, but assuming all 3 probably weren't bad, since they were also from different batches) and still no dice - voltage all over the place between 0-0.5V.

@DailyDovetails I'll do some more poking around and see if I have shorts anywhere (and also yank the charge pump and see if I get voltage to the LED again) - thanks for the advice.

 

[Erik S]

I agree with @DailyDovetails.

I’d be looking for power being shorted to ground. My guess is the blinking on your power supply is that thing going into panic mode.

The short could be internal to one of the ICs which would be nice.

If you set your meter to continuity, you should have no continuity between power and ground. If you do, you’ve got a short somewhere.

 

[Robert]

So this was previously working properly?

Any chance the pedal had reverse polarity or plugged into a power supply higher than 9V (or unregulated)?

Have you tested the power supply with another pedal since the problem began, just to be sure the problem isn't the power supply?

If the short is still present with all ICs removed I'd be suspicious of the 1N4742 zener diode.

 

[ddavis20341]

Everyone here was dead on - yes, there is a short from power to ground. I tried removing all ICs, re-flowing the joints in case there were any short I couldn't see, cleaning the board, etc.

Robert, that's kind of where I was leaning as well. Yes, it was previously working, and tested with a known working power supply (Truetone CS12). I don't think any of the above happen, but it's not out of the realm of possibility (esp. the accidental plugging into a supply higher than 9V on the CS12).

I'll see if I have any extra 1N4742's around and try swapping it out if I do.

 

[ddavis20341]

It looks like I don't have a 1N4742, but do have a 1N4744A - is the only difference in application just higher voltage protection (15V vs 12V)?

 

[Robert]

For troubleshooting purposes you can just remove it.

The circuit will work perfectly fine without it, just don't apply more than 9V.

 

[ddavis20341]

Yep, that was the issue! I took it out and no more continuity between power and ground. And then all good once I plugged it in.

Thanks for all the troubleshooting help - I'll get a fresh one in and should be all good to go.