Bimax 132 welder broken wirefeeder

[metiz]

Not a great week. Yesterday I blew up two anglegrinders in a row and today I fried my welder. The wirefeeder is dead. The torch is fine, it reads 20.8 volts but when I measure the motor that controlls the wire feeder there's no voltage at all. I made a couple of pictures with some clarification here and there. Is there anyone that knows a thing or 2 about electrics or welders? It's a Bimax 123

This is the front of the welder


Rear of the welder


Better look of the pcb at the front of the welder

[Jonny]

That relay (pic 3) looks pretty well used and if I'm not mistaken, rusty on the inside? Definite starting point.

[Joule Thief]

Check for movement of the relay contacts when you pull the trigger on the gun. If the relay is rusted or has difficulty engaging the contacts, you will not see voltage applied to the wire feed motor and no wire will move into the gun.

Relays can usually be unplugged from the PCB, others may need to be unsoldered. Once off the PCB remove the plastic cover and check the relay contacts for pitting and freedom of movement of the contact arms.

[Joule Thief]

This is a representative schematic of a variable speed feeder power circuit.

http://www.mig-welding.co.uk/forum/threads/anyone-got-mig-pcb-schematics.17601/

[G7PSK]

I am not sure that this welder has a contactor for the weld current, it could be a live feed unit and only the motor is switched on and off by the trigger on the torch, the first test I would make is to short the switch contacts on the torch connection and see if the motor starts all to often the switch leads break just behind the torch handle, with large welders you can hear the main contactor working or not as the switch is pulled but many of these small welders the transformer is switched on all the time with only the feed drive operating from the torch switch

[metiz]

Hey guys thanks for all the replies.

I've posted this problem on several forums. After some testing, I'm about 90% sure that the relay is at fault. The metal tab is indeed rusted and the relay does not engage in any way when I push the trigger. The trigger itself is fine. The 2 metal leads that lead into the trigger read 20.8 volts and when I hit the switch, the metal leads make contact with each-other and the voltage drops to zero, ruling out a broken cable.

I unsolderd the relay from the board and tested the coil resistance for good measure. It reads something like 1.15 Megaohm, way too much. I already orderd a new relay, but that'll take a while to arive.

[metiz]

In the meantime I have a different problem. I disconnected a 4 prong rocker switch from a pressure washer pump to get the pump out of its housing. I made a picture of the wiring before doing so but the picture got deleted before I had a chance to upload it. Does anyone kow how to wire this thing back up?
The blue, white, light-green and green wire with the tabs attached need to go on the switch. Back and front of the switch are on the left.

[metiz]

Alright the relay FINALLY came in. I promptly solderd it to the board and turned on the welder, only to be greated by sparking right at the edge where the relay meets the pcb and partly inside the relay, between the most right pin and its opposing twin on the other side of this image. (image not the actual relay, but same pinout) I double-checked the solderjob and it's immaculate, indistinguishable from the other solders. What's going on here...