Valhalla build issues

[xploited]

This is far from my first build, ive built plenty of pedals including 5 working ones from pedalpcb and a few amps over the years but im running into issues with this valhalla build and im unsure where to go.

It presents as a signal that cuts in and out both bypassed and active and after a bunch of debugging seems to be a power issue, the buffer and subsequent tl072's are not getting enough voltage.

Initially I assumed the LM78L12 I had was my issue even though the datasheet was essentially the same as L78L12 so I finally got some of the proper L78L12's today and plugged them in hoping that would resolve the issue, it did not.

I have the incomming 9v from the power source on pin 3 of the L78L12 (VIN), but pin 1 (VOUT) which connects to the charge pump is 7.3v. The +12 and -12 reference points above and below the tc1044scpa are also not 12v/-12v. r31 / c26 point is 7.3v and r29 / c24 seems way off, 110mv.

I ordered some tc1044scpa from a different source.. so maybe thats the issue but figured id make a post incase someone saw something or had any ideas.

Pics were to big so i threw them up on imgbb as well for higher res

20220817-162500

Image 20220817-162500 hosted in ImgBB

ibb.co

20220817-162315

Image 20220817-162315 hosted in ImgBB

ibb.co

any help would be greatly appreciated! All the others (tyrian, hyped fuzz, dirty sanchez, sanguine, etc) from pedalpcb worked perfectly but this one just refuses to cooperate!

 

[fig]

I see the underbellly pots are lifted, but just a reminder they will likely need to be insulated before putting in an enclosure.

 

[xploited]

yeah absolutely, i have dust covers for them just haven't put them on yet, it hasn't went into the enclosure. The 3 lifted there are just to access underneath

 

[fig]

Resistors and what caps I could read check out.

 

[Chuck D. Bones]

Your IN & OUR cox cables are suspect. There could easily be an intermittent short between shield & center conductor. I see melted insulation on the OUT cable. It's rare that shielded cable is needed inside a pedal.

Replacing parts at random is not the preferred troubleshooting procedure.

 

[xploited]

Your IN & OUR cox cables are suspect. There could easily be an intermittent short between shield & center conductor. I see melted insulation on the OUT cable. It's rare that shielded cable is needed inside a pedal.

Replacing parts at random is not the preferred troubleshooting procedure.

Thank you for your reply.. however if you search the form you can see multiple places people suggesting shielded cable specifically for this pedal. It was the same issue when i used the pedalpcb little board with the dc jack and 2 pcb mounted 1/4 inputs with non shielded cable.. given the non standard wiring (compared to oterh pedalpcb pedals ive made) of this pedal i thought maybe that the board might be the issue and used just standard panel mount components and shielded wire as these forums suggests.

Aside from that im pretty confident there is not in fact a short in the cable.. however for the hell of it and to humor you i removed them and the same power issue is there, so this is obviously unrelated.

I'm not sure why you would think my part replacement has been random. The LM78L12 didn't seem to be working correctly so i replaced i with the suggested L78L12. I had a spare TC1044 which i also put in and tried at the same time.. There also isn't many components in this section of the board for it to be... It goes directly from the l78l12 to the tc1044, which has a few caps. What exactly is there to replace other then those two components if the voltages going into the charge pump are incorrect?

Maybe instead of telling me it shouldnt be random suggest some sort of path of non randomness?

 

[Chuck D. Bones]

1. VISUAL INSPECTION.
2. DC voltage measurements at the inputs & outputs of regulators & power converters as applicable.
3. DC voltage measurements at the outputs of opamps.

We're on step 2 at the moment. The +9V rail is at 7.3V and the -9V rail is essentially at ground potential, which tells me the -9V rail is shorted to GND somewhere. Try pulling the opamps and see if the -9V comes back.

You say "...cuts in and out both bypassed and active..." This sounds like an intermittent connection or short. Or did you mean something else?

C5, C9 & C12 are all installed backwards w.r.t. the Build Docs, but that would not cause this problem. In fact, the polarity of those three caps does not actually matter because the DC voltage across them is a few mV at most.

 

[Dan M]

I would still be stuck on step 1: Are there any bridges where there should not be a bridge? Either untidy solder or a loose strand of wire?

It’s difficult to verify from the picture that there is no bridge between the solder pads of IN and Ground, OUT and Ground, + and -.

Is the foot switch continuity correct in both positions?

 

[music6000]

As Chuck as noted, this is not Good!
Have you checked for Continuity across your IN & GND Pads??