My PS02 voltages are off

[nictoafilmscore]

After installing 2 new channels of A12, I was having problems with my other A12s and N72s. I disconnected all the cards and just measured the power supply. The readings that I got were very strange...

pin1 +26.8v
pin2 0v
pin3 -15.5v
pin4 0v
pin5 +48v
pin6 0v

I really don't know what happened with the -27v. Any suggestions?

[tpryan]

The first thing to check is the input voltage to the LM337T (pin 2 or the tab). It should be about 37V with no load. Next, make sure C27isn't shorted (It sounds like it isn't). If those two things check OK, I'd replace the regulator and see what happens. Let us know what you find.

[nictoafilmscore]

I forgot to mention that my 48v was out as well. I'm almost positive its a regulator problem. I touched pins 5 and 6 when I was testing the voltages with one of my leads. Heres what I found after putting the VOM on the regulators:

u1
1: -14.7v
2: -35.6v
3: -15.3v

I checked r3 and r4 in circuit and those both came up pretty close to where they're suppose to be.

u2
1: +25.6
2: +26.8
3: +35.6

u3
1: 0v
2: 0v
3: +71.5v

I also checked r10 and r11 in circuit. Those too are about where they should be.

I cut out c1, c2 and c3 a while ago per Tim's instruction that they're not really needed and tend to fail short anyway (I had c1 burn up one time).

I believe u2 (+V rail) is still fine, but u1 and u3 are probably toast. Am I right about this?

[nictoafilmscore]

Huh.

Changed the regulators today. Phantom is back up. I checked the negative rail of the supply and it was still about -15v. Just for the heck of it, I attached an a12 and put the meter on it again. This time the pins read:

1 +27v
2 0v
3 -27v
4 0v
5 +48v
6 0v

All what they're suppose to be. I don't get it? I thought to get the -27v, you didn't need a load with the PS02? Anyway, I haven't run signal yet, but all the voltages seem to be OK...

Tim? Anybody? Whats going on here?