Your assistance please?

[Cardboard Tube Samurai]

Debug time. I have a DOD OD250 and a Buff n Blend in one box (makes for great bass overdrive by the way!). Now this thing was previously working but had a bit of a faulty switch or at least what I suspected was a faulty switch; occasionally when switched on, it would just be a farty, gated sort of sound. Anyway, so I swapped the switch over and it no longer works at all. I have been debugging it and discovered that the IC voltages are way out.

My measurements:
Pin     Voltage
1        0.02v
2        8.01
3        8.84
4        0v
5        0v
6        8.78v
7        9v
8        0v

What they should be:
Pin     Voltage
1        >0.1v
2        4.5v
3        3.6v
4        0v
5        >0.1v
6        4.5v
7        9v
8        .0.1v

I used the GGG layout (schematic can be found here ---> http://www.generalguitargadgets.com/diagrams/dist_250_sc.gif)

The only change I made was increasing input cap for better bass response so it doesn't make sense. It WAS working but isn't anymore and I'm quite confused. Can anyone help?

[aron]

Somehow the VRef is off - like the V+ is shorted to the pins that should be biased 4.5. It's also possible the op amp is blown.

[Cardboard Tube Samurai]

I have tried 2 op-amps though with the same result (didn't check the voltages on the 2nd op-amp come to think of it). One is a metal can version and the other is the standard silicon version. I shall try a third and see what happens eh? Unless there's something that's blowing them, in which case I don't really want to keep trying it and would rather find the problem.

[DougH]

It's probably not the IC but the Vref voltage divider. Something is messed up as it should be giving you around 4.5v.

[Cardboard Tube Samurai]

Found it! Thanks guys, you at least pointed me in the right direction. At some point during construction, I had accidentally switched the position of 2 of the resistors in the voltage divider and when I had swapped them back, I applied too much heat and lifted a copper trace. Evidently, I had a dry solder joint where I had tried to repair this and it must have just completely broken when I was moving things around to replace the switch.

Thanks again, I knew I could rely on you!

[DougH]

Cool.

[aron]

GREAT!!!!!!!!!