Switch mode PSU failed. Need help repairing.

[Nick9one1]

I nearly posted this in the repair section for the forum, but as I'm a beginner it's probably better here...

I have a smps from a Reebok treadmill. The treadmill doesn't appear to power up at all.

I've ordered a complete set of caps, tested the diodes and bridge rectifier. The coil also seems to be good.

I've got as far as testing the DC output of the bridge rectifier.

What should I do next?




Thanks!

[Wimberleytech]

Find out which SMPS chip is used.
Download the datasheet for that chip.
The example application schematic in the datasheet is probably close to what you have on your board.
Identify and check each component in the power supply circuit--using the schematic as your guide.
Replace the chip of all other components check out ok.

When testing the supply you probably need to load it in order for it to work properly.

[ratatax]

Most smps have a double diode with common pin in a mosfet-like package, usually on a heatsink like the switching mosfets. You can check if it's not shorted.

[stevelup]

Which bridge rectifier? The big one on the heatsink, or the little round one?

The stuff on the heatsink that you have removed has nothing to do with this unit powering up - that's all the drive for the main motor.

The power supply part of this board is the bit by the 8 pin DIP package.