Bizarre Kingslayer issue

[warriorpoet]

So I had a working, lovely Kingslayer, and now I have a strange issue...

For whatever reason, I plugged in last night and got an unholy LOUD buzz, and no LEDs.  I pulled the back off an measured the power at the jack and it's 1.6v.  Intrigued, I checked the boad measurements and IC2 pins 1 and 8, same thing, and IC2 gets HOT.  I've been working with it a bit tonight, and it appears there's a short somewhere between + and - before IC2; when I plug it in to a daisy chain all the other effects go "dark".  Unfortunately, I can't seem to pinpoint the problem.  Any ideas?

[warriorpoet]

Update: eliminated jack, to-board wiring, grounds at jacks.  Might have to start pulling caps here...

[warriorpoet]

Reply 2: One of the resistors on the buffered bypass switch had a broken lead.  I fixed it, and still the same issue, only now voltage readings are in the 0.86v region :/

[midwayfair]

Yikes. First, you're going to have to eliminate shorting on the box as the source of the problem. Just unscrew all the pots and lift the PCB out, see if the short is still there. Did you insulate the pots from the PCB? Make sure that insulation isn't punctured. If you still have the short, you'll have to eliminate the enclosure entirely from the equation by desoldering the PCB and moving it to your testing rig. If you still have the short on the test rig, you'll at least be able to get to the parts easier once the effect is out.

[warriorpoet]

Thanks Jon.  I've already pulled the effect out of the box.  I'm using Barry's pot condoms from GuitarPCB, so at least I know that's not an issue

[Scruffie]

Just a hunch, remove the zener diode...

[warriorpoet]

Just a hunch, remove the zener diode...

Yep.  That's it.  Thanks, Scruffie!

...wonder what happened there.  Any ideas?

[Scruffie]

It has no current limiting, if a zener fails it will eat as much as it can so it dies, becomes a dead short and that's what happens, shunt regulators (zener voltage regulation/protection) are not particularly reliable. If you wish to include it to protect your charge pump, add a small series resistor from your 9V jack to the board, 47-100R should do it.

[madbean]

Thanks for pointing that out, Scruff. I will include the resistor on future boards, or at least recommend adding it from the DC supply.

[warriorpoet]

Thank you Scruffie.  I will do that.  I have ~250 100R resistors sitting about doing nothing, and it's good to find a use for them.

[selfdestroyer]

It has no current limiting, if a zener fails it will eat as much as it can so it dies, becomes a dead short and that's what happens, shunt regulators (zener voltage regulation/protection) are not particularly reliable. If you wish to include it to protect your charge pump, add a small series resistor from your 9V jack to the board, 47-100R should do it.

Great catch Scruffie, I wish I can help out in these section more but for now I use them to better my knowledge and these kind of tidbits are great. Just wanted to say thanks for taking the time to help and dropping some knowledge on us.