Behringer C5A schematic

Got one of these that powers up for a second (blue led comes on) and then the fuse pops.

Opened it up, looks like a basic off-line SMPS (uses the TOP245Y device) and the class D switching amplifier (TDA8932B in BTL). There's some simple input circuitry for the line signals as well.

Initialliy looked for a PSU crowbar, but there does not appear to be one. So next guess is that the amplifier gets unmuted maybe after a second and the output drivers are shorting. The speaker appears OK.

Anyhow, just curious to know if anyone has a circuit or has traced this before I go in and do the same (no circuits could be found elsewhere and B don't release circuits into the wild).

cheers,
Geoff

For those that might be interested.

SMPS uses a TOP245Y off line switching device. Has mosfet and integral oscillator and error amps. Transformer isolated (plus opto regulation feedback) switching at 132kHz. The design is pretty much from the data sheet example for a 30W SMPS. It generates a +/-12V rail.

Amplifier uses a TDA8932B class D switching amplifier in BTL mode to drive an 8 ohm speaker. Design is similar to the dual-rail BTL example in the data sheet.

Pulled the transformer and powered the amp and input circuitry from a +/-12V external supply. All worked well, indicating that the likely culprit is the TOP245Y SMPS device. Should have another one in a week or so to replace it. All other components look OK, and the HVDC capacitor checks out OK.