SMPS Repair

[iamdarkyoshi]

Hello everyone, I have a TV in my garage that I need to get working. It was working fine, but I think the manufacturers didn't screw the PSU down hard enough. The heatsink on the power supply touched the metal mesh that shielded the PSU, and that heatsink was connected to the negative capacitor through two 0 ohm SMD resistors, which exploded. It also made a mess around the feedback traces from the optoisolatosr, so I cut those traces and cleaned the area, running bodge wires where they needed to go instead. I replaced the exploded 0 ohm resistors with wire.

Powered it on, and it just sits there ticking. Its a 3 rail PSU, one rail handles the backlight, and the other two are in a group (they were the damaged ones) and they run the mainboard.

I figured that the PSU's driver chips were probably bad, so I just bought a replacement PSU from ebay. However, it arrived damaged. I messaged the seller about it, waiting for a response. Some traces on the output side were broken, so I repaired them before connecting the PSU.

After repairing them, I installed it into the TV, and applied power. But the new PSU makes the ticking noise as well....

So I unplugged the backlight and mainboard (so the only thing left is the mains input) and both PSUs STILL made the ticking noise.


What could be at fault here?

[carl_lab]

Ticking sound (hiccup mode) is probably shorted PSU output (or short on PSU itself).
Can you measure resistance from +supply voltages to GND at the TV side (with PS unplugged)?

You also tried PSU only (without load)?
Some SMPS need a minimum load to start...