C1 is toast.

[nictoafilmscore]

I opened up my chasis today after smelling some smoke during a recording session I was doing a few days ago. I had 2 N72's loaded in the chasis and they seemed to be working fine. Anyway, I looked at the 72's; they were fine. I looked at the PS02, and c1 was pretty burned. Does anybody have an idea why this might have happened? Could it be anything to do with the way I built the N72's. The PS02 was built by Tim (came built when I ordered the chasis). I do quite a bit of building, but everybody knows troubleshooting is always a work in progress... I know there's some sharp guys and gals(?) that hang out here. Any suggestions would be greatly appreciated.

[tpryan]

C1, C2, and C3 are tantalum bypass caps that can improve the transient response of the supply. If used exclusively with our preamp modules, however, they don't do much to improve performance, since the modules have additional regulators and bypass caps closer to the loads. You can snip all three of them out and not notice a difference in performance. Since they're tantalum, they tend to fail short, which produces the symptom you describe. It's very unlikely to have anything to do with the N72s, and more likely just a bad cap. I'd just clip it out and not even bother replacing it.

[nictoafilmscore]

Well Tim, thats good and bad news. I put a meter on my power supply the other day and I was getting +27v, but I was not getting -27v? I was getting a very low voltage and it wasn't negative. I'm still getting 48v from the right pin. I was hoping it might have somthing to do with the cap. I hope theres not bigger problems with the supply

[tpryan]

If you take a look at the schematic, you'll see that C1 is directly across the output of the negative regulator. If C1 shorts, J2, pin 3 will be pulled close to ground. You should remove the burned cap and see what happens. If the -27V doesn't return, let us know.

[nictoafilmscore]

Right again Tim! I don't know much about troubleshooting but looking at the schematic, thats kinda what I thought it was. Figured I'd consult the experts before messing anything up further than I thought I already did . I clipped out the cap and fired up the PS02. Everything seems to be fine now! Got 2 working N72's and 2 working A12's!

I thank you ever so kindly for supporting your product as well as you do!

[compeq]

I had the same problem. When I fired up my PS02 for the first time, C1 went up in smoke.

Be careful when putting in C1 that it is going the right way.
C2 and C3 can be deceiving.  eg:  +o(C2)o-    -o(C1)o+    +o(C3)o-

I had installed them so that they were all facing the same direction instead of looking to see where the little + sign was on the PC board. The good news is that once I installed a new C1, everything worked fine and apparently no damage was done to the rest of the unit as it is now powering my two A12s.