Oxford mig 150 problems can anyone help?

[Chris85432]

Hi folks I'm Chris I'm new on here, I have an old Oxford mig 150 turbo (think it was made around 1995) and am having problems with the PCB, the problem is when the welder is switched on it switches the relay that controls the gas and the power to the wire on ( but not the relay for the wire feed), so I took the pcb out and had all the components checked by a guy who repairs pcbs and he concluded that it must be the transistor ( To-92 type), however the numbers on the transistor were aparently not visible and when he sent it back the package contained no transistor ( apparently was in there when posted) , so I am now stuck with the problem of what transistor to put back in there to get the welder back working? Any help would be much apriciated as I need to fix the mrs,s horse lorry and if I don't they may never find my body! Great forum by the way there is a lot of very helpfull info on here!

 

[Fintray]

Try here:
http://www.ebay.co.uk/itm/WELDER-PCB-REPAIR-SERVICE-Most-circuit-boards-can-repair-/121080848106?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1c30fb1eea

 

[Jim_gsxr1000]

Welcome Chris

 

[mike 109444]

Welcome chris. The tranny is not stuck between the fins of the heatsink on the left side of your pic is it?

 

[Chris85432]

Hi mike thanks for your reply, I'm not sure what you mean by stuck?

 

[the snooper]

he means has they guy clipped the transistor back into the heat sink where it belongs

 

[Chris85432]

Ohhhhh yes it's in there ok, the transistor that is the problem is the one which Is missing from the board, they are a D shape if viewed from above I believe they call it a TO-92 type it is marked it the board as tr1?

 

[shenion]

A picture of the back of the board may help. Looks to be just a general-purpose transistor.

 

[armalites]

The TO-92 only refers to the dimension/type of physical package.

Why did he not just replace the transistor if he had diagnosed it?

It may be a mosfet, be aware some are very sensitive to static and can be easily killed just by removing or bad handling.

I had a problem with my Migatronic and had to replace only due to resoldering the joints.

 

[Rosepuds]

Hi Chris. I have repaired these PCB`s in the past. I would be able to work out what the transistor is if I have the PCB so I can see the circuit and do some tests. Please PM me if you would like me to repair it.

 

[keith19]

Haven't seen this pcb before, so can't say for certain which transistor it would use. But it looks like a TO 92 could fit in as indicated below. Some of the Clarkes use a NPN F930 MPSA42, but the Oxford may be quite different.

 

[Tin Can]

I have a Britool 161 mig from about the same period which was basically an Oxford Welder badged as Britool - within a couple of weeks i had a problem with the rotary control on the pcb (the small blue componant bottom left of your picture) so i rang Oxford welders who sent me out the complete pcb as per your picture - basically the problem i had with the rotary control was that a spacer hadnt been inserted between the welder front panel and the pcb and i noticed that the nut around the rotary control wasnt tight so me being picky decided to tighten it which pulled the blue rotary control from the board. As i still have the orginal pcb i will have a look tonight to see how it compares to yours - Mark

 

[Chris85432]

Thanks mark that would be really handy!

 

[mike 109444]

Thanks Keith19 that was what I was suggesting. Could be between the fins and the relay. Not a lot of help though if there are no markings! Sometimes the semi removed markings can show up under a strong light and magnifying glass when tilted to catch the light right.

 

[Wedg1e]

Thanks Keith19 that was what I was suggesting. Could be between the fins and the relay. Not a lot of help though if there are no markings! Sometimes the semi removed markings can show up under a strong light and magnifying glass when tilted to catch the light right.

Sometimes a bit of saliva helps show up transistor and IC markings too, can't remember how I figured that one out!

 

[Badger1bear]

Hi Chris welcome to the forum, is the horse box quite rusty seems anything to do with horses and what comes out the other end always gets rusty bad LOL

 

[normspanners]

Have you smelt the exhaust fumes from a horse no wonder things disappear !

 

[Badger1bear]

Have you smelt the exhaust fumes from a horse no wonder things disappear !

Sadly the other half has two of the critters but it does allow me to buy nice toys because I get to see the vets bills

 

[Tin Can]

Heres a couple of pictures of the pcb, although different very similar. See what you think - Mark

 

[Chris85432]

Hi mark, that looks pretty similar can you tell me what the numbers are on the side of that transistor?