Kingslayer - weird failure

[mlabbee]

Playing through my Kingslayer just now and I yanked my guitar cable out of my guitar. The plug hit a metal chair on the way to the floor and my board went quiet except for a very low level thumping.  It took me a few minutes to figure out what had died as power to everything was out.  At first I thought I had managed to fry my 1-spot but I finally discovered it was the Kingslayer - I noticed a little smoke coming out of it and smelled some burning plastic, so I yanked it immediately!  I opened it up and the quad op amp appears to be the smoking culprit - either pin 4 or 5 (both are burnt).

Any thoughts on what might have happened? Would a short do something to the power supply?  It was on at the time it happened (I built the buffered version). 

I'm wondering if I should replace the charge pump as well as the op amp of if it's even worth it (i.e., did I really fry it?)

[electricstorm]

Unless the Kingslayer is different, you guitar cable shouldn't have caused the op-amp to fry when it hit the metal chair. The input should be buffered or at the least have a resistor or capacitor going to the input. Sounds like possibly an overvoltage problem or an internal short somewhere. Are there any bare wires that carry voltage touching the pins of the op-amp?

[mlabbee]

Here are a couple of pics - hopefully they are clear enough.  I can't see any obvious shorts.  The board is seated on 3M double sided foam tape and one of the hard clipping diodes is missing (lost it when I was assembling and waiting for a replacement - the other clipping option is intact, though and that's how I was running it).

There are a few bare wires in there, but they appear to be clear of any contact.

[mlabbee]

I should also note that the pedal has been working fine for several weeks, with a fair amount of usage, solidly attached to a pedal board (so not a lot of jostling).  You can see the melted bit of the socket next to the op amp blew between pins 4 and 5.

I'm wondering if the cable incident could have sent in some kind of signal spike or messed with the grounding in a way that damaged the op amp or charge pump?  The Kingslayer was third in line behind a NPN Rangemaster clone and a Bozz FZ-2.  All pedals operating off the same 1 Spot on a daisy chain. 

I just added a Mad Professor compressor behind it (doubt I'm anywhere near the current draw limit of the 1 Spot - could a current problem cause a failure like this?

[mlabbee]

No thoughts anyone?  Looking at the pin out of the op amp, pin 4 is V+ and pin 5 is ground.  So if there were a short between these two pins, you'd just be draining the full power supply to ground, right?  That would explain why everything on my board went dead. 

So the op amp was blistered right between the two pins - would this happen if the short were external to the pin?  (I can't find any evidence of a short on the board or in the wiring that would bridge these two pins). Is there any way the op amp just failed due to an internal short? I've never had an op amp go on me before, but I don't understand why the Op amp would blister between those two pins if the short were external . . . .

[mlabbee]

So, I went over everything and couldn't find a problem, so I popped in a new op amp and it's working fine.  Seems incredible, but I wonder if I just had a very rare op amp failure?

[electricstorm]

It is possible that the op-amp suffered from some ramdom failure. I have seen different IC's fail for no reason in the past.

Glad it is working. Hopefully it will be fine.

Jim

[mlabbee]

I thought it was okay, but when I played it at volume, I can hear a strange fuzz as the note decays. Sounds like some kind of power supply issue.  I'm guessing something else got fried when the op amp blew.  Sigh . . .