Guitar pedal Virtual ground oddness and repair help

[jwhmca]

Hi Guys,

So I have this power supply in the schematic the +12vdc is not running and I'm pretty new to this virtual ground thing. I've drawn out the schematic and trying to see why the LM7912 is working but not the LM7812.

How could it with no power on it? How can I be getting these voltages? I feel like I'm missing something...

Any insight?

 

[JohnRoberts]

If the transformer secondary has no ground connection it will make a +/-  DC voltage that floats wrt ground. If the + supply draws more current it will pull down the + side resulting in more - voltage like you see.

JR

 

[jwhmca]

I forgot to mention it works just fine with batteries, but of course at a lower voltage. Taking the LMXX12's out of the equation(?)

 

[jwhmca]

One thing I don't understand yet is how the +/-12vdc get past D1 and D2?

**edit** duh! stupid datasheet look below .

 

[jwhmca]

M3E vs M3D???

Which is which?

 

[jwhmca]

Bad 061AC