Hi wonder if anyone can help me my sealey mighty mig 150 now welds with very poor penetration regardless of what setting its on,ive checked all electrical connections
The problem could be due to a poor connection ( i.e. a high resistance ) on the low voltage, high-current welding circuit.
Start by checking the tip on the MIG torch, and the clamp and cable on the work return lead ( known as the "earth cable" ).
Then unplug the machine and check inside, looking for loose, burnt, or corroded connections on the thick wires and joints. Check all the bolted joints at the rectifier and the inductor ( choke ). Even if joints look good externally, they may be corroded or crumbling inside. A frequent source of trouble is the spliced and sleeved joint at the internal end of the work return cable.
You could check the voltage between the torch tip and the work clamp. Expect about 15 volts DC, rising to maybe 30v as you step up the welding power settings.
Sometimes the power switches themselves fail. They can arc and burn inside, or the push-on cable tags may be loose.
They carry AC mains, so power-off and unplug before checking them.
When the torch trigger is pressed, a relay on the control board may close to power-up the welding transformer. The relay contacts have a tough life, so, if they are visible, check for signs of pitting or burning.
I use a sealey 180 and was prone to burning the contact on the earth lead just inside the welder ,, you will soon see it when the lids lifted off though