SPA POWER9, Power supply repair - Successfull repair

[David97]

Not a question. Thought I should post a successful repair, in case someone else has this issue, hopefully it will help them out if they stumble on this post online. Just leaving a document of my repair online. I found several documents of people trying to repair this unit. But they could not due to part numbers being scrubbed off, or components destroyed to a point where they could not read the numbers.

Disclaimer - Messing about with power supply is dangerous. Capacitors can hold charges hours. Even with the device unplugged, there is the potential for a nasty, or fatal shock if you don't take precautions. If you don't feel comfortable with this disclaimer, then just spend the $ to buy a new unit.
After any test, leave it disconnected for several hours, and make sure you short out the caps to discharge them before working on the unit. If you don't know what you are doing with electronics, then this is not a thing you should be messing with. There is a lot that can go wrong.
A easier and safer option would be to just install a equivalent rated PSU in the box.

During the testing, I was sure to never touch the board. I had a light wired in series, as a ballast. So if the unit went dead short, it would not trip the breaker or blow a fuse.

This PSU was dropped into my hands after one of my mates spa pool stopped working.



The first thing I noticed was the SMPSU IC was blown. The IC had a crack in it, and a obvious skid mark. The part numbers were scrubbed off. I reverse engineered it, and replaced with a TOP247YN
https://www.digikey.co.nz/product-detail/en/power-integrations/TOP247YN/596-1078-5-ND/865354

The output rectifier diodes were shorted. Part number MBR25100CT. I replaced with a higher rating, using MBR30100CT. Since these diodes blew, there is the potential that the capacitors on the output have seen some AC, and should be replaced too.
https://nz.element14.com/taiwan-semiconductor/mbr30100ct-c0g/schottky-rectifier-100v-30a-to/dp/3519354?st=schottky%20rect%20100v%2030a

At this point, the PSU powered up, but the voltage was way too high. I adjusted the pot, but it fell apart when adjusting. So I replaced with another 1K trim pot.
The voltage was still not being regulated properly, so I tested the voltage reference TL431 and it tested fine. I tested the optocoupler EL 817, and it was faulty. I replaced with a equivalent opto, and the PSU was now regulating, and operating properly.

As a final thing, I ultrasonically cleaned the board, calibrated the voltage. And then applied conformal coating. Since there was some minor signs of water ingress on the bottom of the board,  wanted to seal and protect against future failures. I sealed up the unit. And hopefully it will be good for the future.