wrong voltages on U1

[jlearman]

Fired it up...no smoke, no explosions....now to measure the voltage on u1.

I swear on my life that when I first measured it I got +14 and -14, but after I turned the R29 and R27 fully ccw, and measured it again, I got +3 v and -14.

I've double checked that u2 and u3 are not switched, but I don't know how else to find out where the problem is. Is there a checkplot for the a12 so that I can find out where the problem is coming from.

Also....Inoticed that u2 gets very hot, but u3 is not hot at all.

Could the problem be from the wiring harness....I don't think I did the best of jobs on that part....

[jlearman]

anyone have any advice on how to trouble shoot this? My N72 is working fine, so it can't be the power supply or wiring harness. I've double checked that all the caps and diodes are installed correctly...that the LM317 and LM337 are not switched...tried most of the obvious stuff, but would love a way to narrow down where the problem is.

thanks again,
joe

[tpryan]

If U2 is hot, you probably have a short somewhere. Is C4 installed the right way round? Try removing it and see if your voltages return to normal.

[jlearman]

C4 was the problem....turned it around at looks like it's working fine. Thanks Tim!