Miller Maxstar 150 HF problem

[James1433]

Hi i have an old Miller Maxstar 150 with the separate Soft start 1 unit underneath. I had just finished using it the other day and had the earth lead on a bit of plate i was using to rest the job on. I put the torch down on the plate and after a few seconds the torch started arcing out and the HF was buzzing. I switched it off and lifed the torch away from the plate and then switched it on again but now it constantly buzzes. I took the casing off this afternoon and traced the problem to one of two things. The resistor (at least i think it is) is getting very hot! Or the circuit board for the HF. There is a contact with a small gap that was arcing all over the place (can be seen in the pic bellow) so i cleaned that up and got a better spark and hoped that had fixed it but no. So do i need to try and find the HF curcuit board or the resistor or could it be something else? Thanks.

Resistor?



HF Circuit board

 

[500e]

The brown bit is a 500ohm wire wound resistor it is designed to cope with heat they normally fail open circuit, note there are 2 relays on board + what appears to be a voltage regulator lurking near the 2 white connectors, & a fuse under red plastic ? doubt if that is problem the relays are the first things to check, the lh orange cap also looks as if it has started to blow the case, but it may be just the photo.

 

[AdrianH]

May be worth while blowing and cleaning all the iron filling out of the box and giving the boards a brush down. No mains connected of course!

Make sure the trigger is not shorted or the wire to it.

Adrian

 

[James1433]

Ok thanks going to give ita good clean up while it's apart. Can parts still be got for these machines? Would rather spend money and fix this one than go out and buy a cheap Chinese machine.

 

[James1433]

I removed the board yesterday and took it into work as i have a colegue who knows a bit about electronics. He thinks the transistor has failed. Its not clear in the picture but is just infront of the coil. I can get a replacement for 99p on ebay so think it's worth a try. Will keep you updated