Reversed polarity on C13- problems

[mikea12]

Somehow managed to reverse the polarity on C13 and powered it up. Power light was strobing, realized a cap was probably fubar at that point.

Shut off power, unsoldered the cap, reversed its position, re-soldered, powered up. Power light holding steady, 14.6 V+ from U1 pin 4 to U1 pin 3. That's good. ~360.7 mV- from U1 pin 4 to U1 pin 5. This is obviously bad.

Replaced C13, U5, and R32 tested bad. Same result.

Checked orientation of all diodes, they're installed correctly. C4 and C5 are oriented correctly. Having trouble determining if this is a gaggle of bad diodes or... ? Don't think it's a solder bridge, everything looks pretty good on the underside of the PCB.

Turning the trimmer on R25 raises the voltage on U1 pin 4 to U1 pin 3 as expected. Turning the trimmer on R29 also raises the voltage but we're only getting it up to values of .5 V- and obviously that's not the issue.

So... anyone have little feedback? Have searched around and found similar issues but nothing that really matches this situation and no fixes that have helped.

Thanks in advance!

Mike

[tpryan]

What's the voltage at the + side of C13? Is it the same as at U5, pin 2?

[mikea12]

The voltage for the plus side of C13 reads 0 volts and U5 pin 2 starts around 1.5 mV when it is first powered on and falls steadily after that. Thanks the reply, any thoughts?

[tpryan]

What voltage do you measure at the cathode (banded end) of D3? How about the anode?

[mikea12]

The cathode reads 30.09 V- and the anode reads 29.73 V-

Thanks again!

[tpryan]

As you can see on the schematic, the anode of D3 is connected directly to the - end of C13 and U5, pin 2. The voltage should be the same at all of those pins. If it's not, there are open connections somewhere, either bad solder joints or broken tracks on the PCB.