Question re op amp failure

[mlabbee]

Hi all,

I just built a Mad Bean pedals Kingslayer and had a really odd failure.  The details are here (with some pics): http://www.madbeanpedals.com/forum/index.php?topic=7736.0

The quick summary - the op amp failed. It was smoking and blistered between pins 4 (V+) and 5 (ground) (it's a quad, 14 pin DIP).

I couldn't find any external shorts (and would an external short between V+ and ground smoke the op amp or the board?) so I'm wondering if there was an internal short in the op amp. 

I've built a few pedals and never had an op amp go before unless I had wired it wrong but this pedal worked fine for a few weeks before dying.  Has anyone ever experienced a similar failure?  Is there some way a short in some other part of the system would cause an op amp to fail in this manner?  Could the charge pump fail and overload the op amp (no external signs of damage on the charge pump chip).

[R.G.]

Sometimes they just die, but it's unusual. Very rare.

If I ran into that set of situations, I'd suspect that the power supply was reversed. I've killed opamps in a similar way before.

If the board has polarity protection, is it even possible you plugged a power adapter with an **AC** output into it instead of one with a DC output?

[mlabbee]

It was plugged into my daisy chain (powered by a 1 Spot) with several other pedals plugged in. Once I unplugged the (dying) Kingslayer, everything else ran fine.  When the KS was plugged in, though, everything else was dead (except my compressor, which was making a thumping sound.  I assume, the KS was shorting to ground in someway, so the voltage to everything else was zero or very low (why would the compressor thump?)

My theories:
Op amp died
Charge pump failed (and reversed polarity?)
External short to ground (would that cause the op amp to smoke/blister?)

I'm going to get another op amp and see if it fries again . . .

[mlabbee]

Well, I double checked all the solder joints and wires, reassembled it and popped in a new op amp.  So far, it seems to be working fine.  It seems extraordinary, but maybe I did indeed have an op amp just blow up on me . . . glad to have it up and running again - I'm really enjoying the Kingslayer.  If this is really what a Klon sounds like, I can see why people like it - nothing "magical" about it, but it really is a nice OD with tremendous range.