Chinese Giant WSE200 help

[EEEK]

Anyone have any idea what the problem might be?

Had the welder a while but its not had a hard life. Went to use it today and it worked for a minute or 2 then died.

When turned on all seems ok. If you do nothing like the vid there's a click then a few seconds wait and it dies, you can see the green led on the board gradually go out. Power off and on, still dead. Wait a few minutes and it will do the same again.

When it comes on before the 'click' it works, arcs up and welds. 'click and it dies. Not an instant off more of a slow power down.

Its stone cold so unlikely to be overheat. All switches/knobs/settings make no difference. Its plugged in to the same place it always has been and nothing has change from when it worked fine.

 

[eddie49]

The "slow fade-out" implies that it might be a high-resistance joint caused by a loose connection, which then heats up and becomes worse.
The push-on ( 1/4 inch ) spade tags on the main On/Off switch and the four tags that connect AC in and DC out at the bridge rectifier are often loose or not pushed fully home. I sometimes solder them on permanently.
Then all the bolted connections to copper or aluminium busbars, thick tracks on the circuit boards, finned heatsinks, and the rear of the front-panel Dinse connectors should be checked. These are sometimes just finger-tight. Check all the multi-conductor harnesses between the PCBs and their plugs and sockets.

To check these connections, or any others, you will need to remove the casing from the machine. To do this safely, it should be switched off, unplugged, and left for an hour or two to allow the potentially dangerous charge ( 325v DC ) stored internally in capacitors to dissipate.

 

[EEEK]

I've found a few connections that need a bit of tightening. Had a wiggle about at most connections.

So far I think its something to do with the bottom board, that's where the relay clicks. If I disconnect everything off the board other than the power wires it still clicks and turns off.

I've found some instructions/info on the net that mentions a temperature resistor. Not the main ones on the side, they are ok. Its not in the skip yet I'll have a better poke around at it yet.

 

[eddie49]

There is normally a soft-start circuit that sends rectified mains power to the large smoothing capacitors via a resistor or a thermistor, to reduce the initial power-on surge when the empty capacitors are first charged. After a brief delay, that component is bypassed by a relay and the welder is ready to work. It may be that relay which you can hear.

 

[EEEK]

Hmm it works today!!!

When it stopped I had the cover off and a poke around obvious stuff. Had a volt meter on the main bottom board and had a reading of 245v. Didn't think anything of it, on the high side but within limits.
Pulled of various connectors and poked around, nothing to loose or burned, didnt see anything obvious. Kicked it in to the corner for another day....

Today is another day. Armed with my internet diagrams and info I'll have a proper look. Plugged it in and its working pefect!!!

Stuck the volt meter on various places 235v today.

Could it maybe just have been a voltage thing? To much voltage so it cuts out?

If it happens again I'll check the voltage first.

 

[eddie49]

Assuming that 245 volts is AC, then yes, it is a bit high, but it should not be causing any problems.
On most inverter welders, the AC mains does not get beyond the main on/off switch, maybe an input filter, then it is straight into the bridge rectifier. On higher-rated units there may be two of them, in parallel. The DC output then goes via the soft-start surge limiter into the large electrolytic capacitors. Their smoothing effect raises the "DC Bus" voltage to the peak value, which is 1.414 x the rms, i.e. 325v DC, and this runs the entire machine. When you have 245v AC coming in, the DC Bus would be 346v.
**Please note that this is a very dangerous, potentially lethal voltage, and it may remain after the welder has been switched off and unplugged. Only check this voltage if you have the correct testgear and protective equipment, and are confident working on live high voltage circuits!

 

[EEEK]

Yes ac - mains voltage. Through the main switch on on to the bottom board.

I'll not get fried, I have insulated stuff and ppe, work with mains power everday so I know not to touch stuff

Its back together and welded what I was needing it for.