Valhalla pedal doesn't work

[TurboTim]

Hello everyone,

I have problems getting the Valhalla Pedal Kit to work, and I don’t know what else I can try to fix it.

I have some experience with circuit boards and electronic components, and I’ve successfully assembled a pedal kit in the past. However, I’ll admit my soldering skills are a bit... well, let's say, improvable, as I have rather shaky hands. On the other hand, I’ve successfully soldered many projects before and never had problems with cold solder joints or similar issues.
I’ve attached a few photos of my non-functioning circuit board to this post.

When I plug in the pedal, my amplifier doesn’t make any sound at all. It seems like there’s no connection between input and output, both when the pedal is on and off.
The small LED, however, lights up red, and on my multi-meter, I also see ~9V.

What I have tried so far:

• Checking each resistor to make sure it’s the right one in the correct place.
• Checking if the potentiometers are in the right spots.
• Checking if all capacitors are correctly oriented.
→ One electrolytic capacitor was not correctly oriented, but I have already replaced it with a new one in the correct size and orientation.
• Checking all diodes.
→ Since I wasn’t sure if I had placed the very similar-looking Zener diodes in the correct spots, I de-soldered all the diodes and soldered in new ones with the correct part numbers.
• Checking if any of the pins on the input and output jacks are touching the case.
• Re-soldering the worse-looking joints visible in the photos, where one could suspect there might be bridges where they shouldn’t be. According to my multimeter, this wasn’t the case, but I did re-solder some of those spots anyway.

None of this has helped.

Does anyone have a tip? What am I doing wrong? What should I try next?

Thank you in advance for your efforts in helping me.

 

[swelchy]

I see copper showing where you have circled" already soldered" you likely have damaged traces... possibly from being too agressive with trimming your leads or during the resoldering process... some others will chime in with some suggestions but right off the bat i see you may have broken traces..

 

[Erik S]

Whats going on with your switch wiring on the back side of the board here? Hard to see from the pic, but that would be a spot you could short your signal to ground.

 

[TurboTim]

Whats going on with your switch wiring on the back side of the board here? Hard to see from the pic, but that would be a spot you could short your signal to ground.

View attachment 93367

It is the LED that you can see down there
But you are right it almost seems like a short.

 

[TurboTim]

I see copper showing where you have circled" already soldered" you likely have damaged traces... possibly from being too agressive with trimming your leads or during the resoldering process... some others will chime in with some suggestions but right off the bat i see you may have broken traces..

Mhm. That could be it.
I thought earlier something similar about this area. I might have destroyed the protective "layer" there and now my solder touches those traces as well, even though it shouldn't.

How would you try to solve this ?

De-solder everything in this area and put in on the other side of the board, while only soldering on that other side ?

 

[Crowbar]

On one of my builds the input jack was shorted internally, signal to ground.

 

[TurboTim]

Five hours later and unfortunately, I still haven’t made much progress. This is truly one of the most frustrating situations I’ve ever experienced. When you factor in the lost nerves and work time, I could have already bought at least two brand new Diezel pedals. But I digress.

I’ve tried to follow every tip mentioned here, as well as other advice I found online:

1. I’ve definitely checked the input and output jack connectors both inside and outside the pedal at least four times. And they are correctly wired. I also checked for any shorts between the signal and ground.
2. Wherever the solder joints looked questionable (see the photos in my original post), I tried to rework them.
3. Wherever the first layer of the PCB might have been damaged, I de-soldered the components and carefully re-soldered them on the other side of the board so that no solder could come into contact with the exposed traces. All removed components were replaced with new ones.
4. To make sure I didn’t overlook any faulty solder joints, I removed the LED again, as it was covering 1-2 contacts. After that, I installed a new LED.
5. Then I made an audio probe and went through each resistor one by one. I actually found a resistor (R9) that seemed to have a loose connection. So I de-soldered it and replaced it with a new one. After this small success, however, reality set in again. While I now have signal continuity in the broadest sense, the noise and the presence of abnormal sounds are so extreme that you almost have to turn the amplifier all the way up just to hear the oddly ringing guitar in the background.
6. So, I went back to work with my audio probe, and up to about R11, the signal still sounds decent, but from R12/R13/R14/... (also strangely a bit at R10), the signal in both the on and off states is so extremely distorted that it can only be considered unusable. Aside from C10 and R14, all the solder joints here have already been reworked and components replaced. In other words, I don’t know what else to do. ?
7. Finally, I tested the following: Between pins 4 and 8 on IC1, IC2, IC3, I saw something abnormal. I expect to see +/-12V, but I only see +/-6.8-7V. Unfortunately, I have no idea what could be causing this or what I could test/change. Maybe someone here can enlighten me with their wisdom .

 

[TurboTim]

Everything is measured against GND
I have no idea why it does what it does.
In my opinion, the soldering of all the affected components looks fine.
The possibly damaged circuit boards are also located completely elsewhere.
I really don’t know what else I should try now.

 

[jwin615]

Your L78L12 is either bad or something is dragging it down(short pulling too much current)
Pull all the opamps, leaving the charge pump and then remeasure

 

[TurboTim]

Your L78L12 is either bad or something is dragging it down(short pulling too much current)
Pull all the opamps, leaving the charge pump and then remeasure

I wasn't 100% sure what exactly you wanted me to test.
So measured with all IC's mounted and V_0 is ~6.85V as shown in the picture above.
Then I measured with the TC1044 removed and the output is ~7V
Then I measured with the TC1044, but the other three IC's removed and the output is ~7.1V

This might be a dumb question, but isn't the 7812 only be able to reduce V_I, so it seems that it works how it is supposed to work.
And those required +/-12Volt are only possible when I use a Power supply with 15-18 Volt. Or am I wrong about this ?
On the other hand I believe to have seen somewhere that this PCB is suppose to run with a 9V Power supply as well ?

Well, overall I don't really know what to try anymore to make this thing work. Any suggestions ?

 

[jwin615]

I completely missed that you were running this on 9v. Should be 15-18v, but it should still make sound at 9v.
I'm assuming you get bypass sound. If you don't get bypass sound, no need for the lower "power on" section until you get the first bit sorted.
Starting with power off.
-check your footswitch to ensure both polls are switching. Resistance near zero between center lug of each pole and upper/lower pile, switch position dependant. So, 1to 2 and 7 to 8, flip switch, 2 to 3, 8 to 9.

-measure resistance fromin jack tip to put jack tip. One position of the switch should be near zero ohms.
-measure resistance at in and out jacks, tip to sleeve. So in tip to in sleeve, out tip to put sleeve. You should not have low resistance here. If you do, you e shorted signal to ground somewhere.
Assuming those check out, apply power:
-use an audio probe to verify signal at each gain stage. Feed a test tone or a recorded loop into the circuit. Start at IC1 pin 3. If there's nothing on pin 3, you have an issue with your input wiring, a damaged trace or switch. Revisit the above.
If there is signal at IC1.1 pin 3, move on to the output which is Pin1. Using the schematic, move through each gain stage, checking input and output.

 

[TurboTim]

I completely missed that you were running this on 9v. Should be 15-18v, but it should still make sound at 9v.
I'm assuming you get bypass sound. If you don't get bypass sound, no need for the lower "power on" section until you get the first bit sorted.

In Power off, I get no bypass sound at all in both footswitch positions.
In Power on, I get a pretty bad bypass sound, but it is heavily distorted in footswitch on-position and a tiny bit also in off-position. Both with extreme noise in the background (much louder than the actual sound from the guitar).

Starting with power off.
-check your footswitch to ensure both polls are switching. Resistance near zero between center lug of each pole and upper/lower pile, switch position dependant. So, 1to 2 and 7 to 8, flip switch, 2 to 3, 8 to 9.
View attachment 93579
I can see here zero resistance in both footswitch positions. So we are good here.

-measure resistance fromin jack tip to put jack tip. One position of the switch should be near zero ohms. Both is not zero, more infinite
-measure resistance at in and out jacks, tip to sleeve. So in tip to in sleeve, out tip to put sleeve. You should not have low resistance here. If you do, you e shorted signal to ground somewhere. Both is not zero, more infinite
Assuming those check out, apply power: I shouldn't even bother at this point about the power on status, because it is already evident to be pointless considering the above results. But I did it anyways
-use an audio probe to verify signal at each gain stage. Feed a test tone or a recorded loop into the circuit. Start at IC1 pin 3. If there's nothing on pin 3, you have an issue with your input wiring, a damaged trace or switch. Revisit the above. I remember from doing this a few days ago, but only measuring every resistor connection. I got to ~R12 before the signal went bad. Today I have terrible background noise from the get go, so much so that I don't even hear the guitar when I place the audio probe on pin 3. Strangely on Pin 1 I hear the guitar and the signal is also less noisy, somewhat clean. The same applies to Pin 5 and 6. At Pin 7 the signal is already distorted (footswitch off). Pin 3 at IC2 sounds the same as Pin 7 on IC1, which makes somewhat sense and at Pin 1 of IC2 the signal is even more extremely distorted and weird sounding. Pin 5 and 6 of IC2 are dead, no sound is coming through here anymore. Looking at the all the soldering joints of IC2 I cannot see anything bad
If there is signal at IC1.1 pin 3, move on to the output which is Pin1. Using the schematic, move through each gain stage, checking input and output.

(I commented above inside the quote in red)

I spent now at least 7 hours of troubleshooting on this thing, looking at every single soldering point. I cannot see or find a place where I could have a short on the PCB. I just don't understand.

I'm very very very close to just throw it all in the bin after using a big hammer on it . This is by far the most frustrating thing ever.

 

[jwin615]

It sounds like you have an issue with wiring and jack connections, like the playing at the PCB may be stripped out. Not getting bypass or continuity but your switch testing good indicates an issue between the jacks and switch. If your wires are shorted, that only leaves the wire and PCB trace.
I suspect you could take you in and out wire straight to the center lugs of the footswitch .
@Robert
Are in and out lugs 2 and 8 in this arrangement?

 

[TurboTim]

Well I don't know where to go from here or what else to try ?

Here are my results with the audio probe:

• Without a power supply:
  - The signal reaches input IC1.1 pin 3, after that, it is dead.
  
  
  
• With power supply, but footswitch not pressed:
  - The unwanted noise is generally much higher.
  - From IC1.1 output at pin 1, the noise strangely disappears.
  - Up to IC2.1 pin 3, the audio signal is good, but from IC2.1 pin 1 onward, the signal is just an unbearable, super loud noise, even without any input from the guitar, like a whistling sound
  - At IC2.1 pin 2, the signal is also fine.
  - C8, R10, D3, D4, R11 (The components between pins 2 and 3 of IC2.1) have all been checked again by me. -> No issues found.
  
  
  
• With power supply and footswitch activated:
  - Exactly the same as without activating the footswitch.

No idea what I should make of this??
I've already checked the solder joints around IC2 multiple times, and many of the components in that area have already been replaced, as earlier audio probes showed a similar result. All IC's get the +/-12V, they should get.