EHX Pitchfork+ overvoltage repair

[Phoenix]

Thought I'd share this one for posterity.
Had a customer bring me two near-new EHX Pitchfork+ pedals. He'd plugged one into his Voodoo Labs Pedal Power 2 outputs set to 12V unregulated (open circuit voltage 18V!). The pedal's display functioned fine, but it passed no signal, so he swapped in his bandmates identical pedal, only to have the same result.

Fortunately the 3V3 and 1V3 digital supplies were undamaged, but U7 the 5V regulator with it's maximum input of 16V failed, and this caused a cascade failure of U8 the 5V charge pump inverter with its max 5.5V input range. This +/-5V supplies the analog signal chain. When I received the pedals, +5 and -5 test points were measuring close to 0V under power.

Conveniently both these supplies had ferrite beads on the output, so I was able to desolder these to isolate the +/-5V rails from the main supply, and used my bench power supply to confirm that the analog signal chain was undamaged by injecting power into the test points and ground, along with a regular 9V supply for the digital side.

Both the damaged chips were in the tiny SOT23-5 package, and marked with identifying codes R50 and PFNI respectively.
Figuring out the full part number from these codes was a bit of a pain, but I eventually ID'd them as SPX5205M5-5.0 and TPS60403DBV.
Replacing SPX5205M5-5.0 would be easy, it has a relatively common footprint, and I substituted LP2985-50DBVR as that was what was in stock at my supplier.

TPS60403DBV being more specialised might've been a problem though, and thanks to the current global silicon shortage, almost all of my usual suppliers were out of stock with a lead time of over 12 months. Luckily I was able to find one vender with 15 in stock. I didn't look into substitutions too closely once I found a supply, there may be something suitable, but I couldn't tell you without more research.

Once parts arrived, regular solder and iron, tweezers, liquid flux, solder wick, isopropyl alcohol, a nylon bristle scratch pen, good lighting and steady hands were all that was required. Magnification would help if your vision isn't great, but you don't need any fancy tools.

Anyway, hope this is of help to someone at some point.

[iainpunk]

very nice write up, might come in handy in the future.

i love the pitch fork, super great pedal, but i'd think twice before accepting one for repair.

cheers

[ElectricDruid]

A round of applause for getting stuck in on stuff that size. You're braver than me that's for sure, steady hands or not.

I see tiny SMD and panic, I admit. Maybe one day.