Valhalla issue

[PKRPedals]

I have noticed a couple quirky things with my Valhalla since building it. It has the same squeal/oscillation that my pineapple has when the gain is up around 2 oclock. Also when turning down the eq section all the way, it kills the volume. I run my cable from the power amp out to the front of the amp, it actually sounds better to me this way, and the pedal acts like a mute when you switch it off, but this my be normal for it to do that. Just thought I would bring it up. I have used all my guitars with this pedal and the pineapple and they all cause the squeal. I thought my Les Paul was different but turns out it does it to. These are the only 2 pedals that I have this issue with and I can't seem to figure it out. I reran my cables in the pineapple with shielded cables and that may have helped a bit, but it still has the squeal. My Thermionic and Thermionic Deluxe don't have the squeal. Now with all that said, these pedals sound amazing but I have to roll off my volume just a bit to make the squeal go away. I can deal with it but would rather it work properly. Any ideas?

 

[zgrav]

I don’t have an audio probe, I need to build one.

than make it so....

 

[Chuck D. Bones]

One of the places I want to probe is the power supply rails

 

[PKRPedals]

Chuck
I have been over this pedal with a fine tooth comb. I have checked all the resistors and caps for correctness and orientation. All my diodes are in correct and the correct ones. I swapped out the IC's just to be sure. The squeal is affected by the Treble, Mids, Gain, and/or Presence. It seems to be affected by volume but I think it just makes it louder. If I plug into the power amp out or into the loop, it still squeals. Thoughts?

 

[Chuck D. Bones]

I'm gonna suggest that we temporarily disable one stage at a time to get an idea how much of the circuit is participating in the oscillation. We won't get very far without an audio probe, so you need to make or buy one.

 

[PKRPedals]

Let me make one and then we can continue. Probably be later this week. Thanks for your help so far. This will definitely be a learning experience. I have never used an audio probe.

 

[PKRPedals]

update: Out of curiosity I built another Valhalla. Guess what...It squeals just like the first one. What is it with this pedal? I moved it away from the amp and it still squeals. I saw a Youtube vid earlier and the one in the vid squealed just like mine does. I know others have built this pedal and had good luck. I'm at a loss here. I've watched Youtube vids of the actual VH4 and it doesn't do that. It does get a little noisier when the gain is cranked but no squeal.

 

[music6000]

update: Out of curiosity I built another Valhalla. Guess what...It squeals just like the first one. What is it with this pedal? I moved it away from the amp and it still squeals. I saw a Youtube vid earlier and the one in the vid squealed just like mine does. I know others have built this pedal and had good luck. I'm at a loss here. I've watched Youtube vids of the actual VH4 and it doesn't do that. It does get a little noisier when the gain is cranked but no squeal.

This might Help :
http://guitar-fx-layouts.42897.x6.nabble.com/Diezel-VH4-td43035.html

 

[Chuck D. Bones]

Interesting read. It's easy enough to tell if the charge pump has a problem using a DVM and an audio probe. If the plan is to build another Valhalla without understanding what's wrong with the first one, then I can't help.

 

[music6000]

Try a 7660SCPAZ, Try a MAX1044 also. Pull one from a working pedal!
Post Pictures.

 

[PKRPedals]

Thanks, I will give that a try.

 

[music6000]

Thanks, I will give that a try.

Are you using 9v or 12v to Power it? Make sure your Charge Pump is TC1044S or 7660S.
Someone @ FSB also suggested trying a buffered pedal before it as it worked with their Clone PCB squeal.
Using shielded cable on Input & Output Jacks is also suggested by another.

 

[Chuck D. Bones]

If changing the charge pump does not solve the problem, try pulling out IC1 and see if the squeal stops. If if does, then we know the problem lies somewhere in the circuit near IC1. If the squeal persists, pull IC2. Repeat with IC3, then IC4. At some point, the squeal will stop.

 

[PKRPedals]

I'll try my boss ds-1 in front and see if that works. Thing is, I would like to be able to use the pedal without trickery to make it work. It's either a faulty part or something I did. I'm going with faulty part because I've built 2 and they both squeal using parts from Tayda. Up until this point I haven't had any issues with Tayda stuff, but I guess it was inevitable. Thanks for the suggestion.

 

[PKRPedals]

If changing the charge pump does not solve the problem, try pulling out IC1 and see if the squeal stops. If if does, then we know the problem lies somewhere in the circuit near IC1. If the squeal persists, pull IC2. Repeat with IC3, then IC4. At some point, the squeal will stop.

Ok I will do that this afternoon.

 

[music6000]

If changing the charge pump does not solve the problem, try pulling out IC1 and see if the squeal stops. If if does, then we know the problem lies somewhere in the circuit near IC1. If the squeal persists, pull IC2. Repeat with IC3, then IC4. At some point, the squeal will stop.

Yes Chuck, But after the pulling & squeal stops, will the pedal still work.

 

[music6000]

Ok I will do that this afternoon.

Can you Double Check that your 5232 Zener's are correct values!

 

[PKRPedals]

They are 5232B. Is that wrong?

 

[music6000]

They are 5232B. Is that wrong?

Part Number is Correct, But test it anyway as below:

 

[PKRPedals]

5.4 volts is what I get

 

[Robert]

You aren't the first person to have oscillation issues with this circuit. (and the issue seems to affect several different vero / PCB layouts)

As music6000 mentioned, at least one person found that a shielded input wire helped. It's odd that a buffer in front helps, considering the first stage of the circuit is a unity gain buffer.

(EDIT: Nevermind I see them in your pic and they're correct.)