Dead EHX Cathedral

[Vel]

Good evening/morning/afternoon whatever it is where you are at,

this weekend I picked up a dead EHX Cathedral for almost nothing and I want to take a shot at bringing her back to life. I'll probably open it up properly and start measuring some voltages around the pcb next weekend, but was wondering if anybody here has some pointers or things that could caused this pedal to crap out or maybe someone has fixed a Cathedral with similar symptoms. (I tried googling it, but to no avail.)

According to the guy I picked it up from, it all of a sudden just stopped working. When I plug it in to one of my power supplies (right voltages amperage etc.) none of the LEDs light up (not the bypass one, not the tap one, not the program selector, simply none.) Some quick measurements show not out of the ordinary voltages at the jacks, switches etc. (approx. 4V iirc.)

The only voltage I found so far that is strange to me is 2.5V across the two metal plates on the 2.1mm DC jack barrel inside the pedal. The same component in my big muff tone wicker measures 0V, but I could be wrong about this being off, of course (This pedal is miles ahead of anything I've ever repaired in terms of complexity.)

Cheers!

[Mark Hammer]

That's one complicated pedal.  On the other hand, power-supply problems seem to be universal.  There looks like there might be some simple dual op-amps in there.  Can you measure the voltage between pins 4 and 8?

[Vel]

Thanks for your reply! It sure is a beast haha, but it's a cool challenge I think.

I've 3.8V across U9 (which is a MC33078 I think, the IC saus 33078 PTML)

Edit: Scratch that, I brainfarted and measured across 3 and 8 (off to a good start  ). Theres 10V across 4 and 8

[j_flanders]

A lot of these types of EHX pedals that are dead have a burnt resistor that acts like a fuse. Usually it's something like a 4,7 Ohm 1W resistor.
https://www.google.be/search?q=ehx+burnt+resistor+site:diystompboxes.com

[Vel]

I'll look into that later. If this has that resistor, it's on the other side of the pcb and how EHX ever got that thing inside that enclosure beats me, so thats for some other time haha

[Vel]

Okay, after a lot of violence and nervous sweat I finally got the pcb out. Not looking forward to putting it back, man I don't see how EHX ever got this in there haha.

Sadly this only has smd resistors and none of them seem obviously burned, so I think i'm out of luck when it comes to a "fuse" resistor. Guess i'm just gonna take some measurements over the weekend and try to make some educated guesses then.

I forgot to mention that sound comes through the pedal when bypassed, btw. though I don't think this pedal is buffered, so that shouldn't really matter for troubleshooting.

[cloudscapes]

If you have a scope I would check the 4-5 data lines between the big DSP and the codec IC. Don't need to be able to decode the data, just check to see they are indeed communicating.

[Vel]

Don't have one myself, sadly. I might be able to use one at my uni though, so I might give that a shot. Any specific things I should look for when doing so?