I posted this on LPF first, but thought I'd put it here too just incase anyone had idea's and not on LPF
OK well, a while ago I "bought" a free argon laser from Dave. He offered them without power supplies or any information. Thats fine, I got one anyway.
I originally intended to build a simple linear PSU, however my mains voltage being 240V, I can't just rectify mains and chuck it into a passbank, I'd require about $200 worth of transformers!
I saw that timelablasers had a complete, but broken argon laser for sale, so I asked him if he'd be willing to sell me the PSU. And he did
First obvious things were a FET that was cracked, and a burnt up resistor. He had already replaced a fuse next to the blown FET.
I bought some new FET's and replaced the cracked one, hid behind my kitchen window, and powered the PSU up. It didn't explode, but it didn't do much either.
There is a 200 ohm resistor on the neutral input line. Beside it is a relay. I have come to the conclusion that this resistor is to limit inrush current, and is bypassed by the relay once the PSU has powered up. However, this relay is clearly not doing anything, and the resistor just gets hotter and hotter. No lights or anything show on the board either, just 1 hot resistor.
So, I unplugged it, and being a switchmode PSU, I left it for a while, and tested the tank caps. They had no charge. This could be because they were already drained by other components, or they didn't get any power at all.
The only components between the mains input and those capacitors is the rectifier, and 2 big inductors. I have removed all the boards from the PSU, but have no idea where to start testing for dead components.
I would check the rectifier first, but can I do that while it is still on the board, and with a regular DMM? If the rectifier was dead, that'd explain nothing getting power, but it wouldn't really explain a dead FET, unless the rectifier was killed after the FET (Tube wires shorted or something maybe?) I don't know.
Here are some pics:
Considering the component count on this beast, I have absolutely no idea where to start. The fact nothing seems to get power points to a PSU issue though, so I guess I can eliminate pretty much all the logic circuitry.
Any help or pointers would be greatIf you need any more information, please do ask, I'd like to give this thing a 2nd life instead of having it sitting out in the garage for the rest of it's days
Cheers,
Dan