Not another migmate problem??

Hi all I've been a lurker for to long time so its time to come out .
Now before I get started on the "PROBLEM" with my very very old migmate 100,
I purchased the welder before SIP became printed over everything "migmate",
and until recently has given many happy hours of spotty left forearm syndrome trouble free welding.
I dont have issues with wire feed as many have even with the 5kg reel on,my welder has the adjustment pot (1k) through the front lefthand side of the machine which passes through a piece of aluminium heatsink and out the casing.
The quite large heatsink also attaches to and cools the 3 pin rectifier.
On a couple of occasions recently while working on my very rusty 1978 vw bay window I have had the welder inside the van to keep it dry or out of the sun. As one of its little plastic feet is missing it has grounded the machine and caused a short on the pcb,which without any problem I have repaired and had running again within ten minutes (and a cup of tea ).

Now for the comedy moment just needs a bit of imagination,

Now my dillema is I dropped the torch on the welder which landed exactly on the trigger, as I dropped it knee jerk reaction made me grab for it in doing so I knocked the earth clamp of the piece I was working on and landed on the welder torch tip touched earth clamp and FLASH and POOF is all I can describe it as.The combination as you would expect caused my welder to try and weld itself (not that it needed welding).After blowing the wisps of smoke from the vent holes in the machine I went indoors and flicked the main trip switch back on in the leccy cupboard. I pulled the side off the welder expecting to see complete meltdown, but no all it has done is burn out 2 lines on the pcb and taken out the TIP 35C rectifier,oh and broken the wire feed adjustment rod off on the outside.
When I replaced it some time ago I did'nt cut the 2 and a quarter inch or 56mm plastic bit off cos it made it easier to turn .
Now I've put in a couple of temp wires in to sort out the base of the pcb and got a new 1k feed adjustment pot from maplins, although the welder works again I cant fine control the wire feed and it was suggested the 35c rectifier is fried. But do you think I can find the rectifier not on your nelly.
Looks like I will have to order online, does anyone reccomend anyone that I could phone and order this £2.00 part from.
I know what your all saying why did'nt wotwot just ask where to get the rectifier from, that would be too easy for you peeps to say GOOGLE it and would have been a boring first post.

So hello all keep up the great forum I hope someone can advise me where to get the rectifier from.

Hope I put this in the right place if not could someone gude me on where to post it please.

The TIP35C is a Darlington transistor (not a rectifier).

Farnell would probably have it.

There are very few places these days where you can walk in and they have a reasonable range of transistors you can buy over the counter. I wouldn't count Maplins.


You're pretty much stuck with mail order and watch out for the minimum order charge and P&P.

I find Farnell is more pleasant to deal with than RS, but there are others such as NR Bardwell and Cricklewood. None of then are going to be rubbing their hands together at the prospect of selling a single transistor for a quid.

Here's the datasheet.

http://www.st.com/stonline/books/pdf/docs/5071.pdf

Thanks for the replies so far.
shenion I knew I would get this answer or similar,I can put in transistor, diode, barrier rectifier,(three pin fuse) and get loads of the same result come up on google,
I realise nobody is going to retire on the proceeds of my little sale but someone has to buy the small things LOL.
PTvor thanks for the data sheet already had a look at that one.
do any of you have phone numbers for these suppliers suggested or links many thanks for your help so far.

Farnell: http://www.farnell.com/

Here's another

http://www.cricklewoodelectronics.com


There are a fair few others. The smaller ones such as Cricklewood tend to be better for obsolete stuff which RS etc no longer stock.

Hi again the TIP 35C is well fried.
Maybe a DUMB question but what is the difference between a TIP35C and a TIP36C,I have seen the data on them and they are on the same data sheet side by side.
Is one NPN and one PNP if so WHATS the difference,or put in my terms can I use a TIP36C in place of the TIP35C,or does this throw up more messing with the speed control board.
If you can reply put it in laymens terms for this heavy handed numbskull please.

One is NPN the other is PNP. They are opposite polarity devices.

They are a complementary devices normally used where an output needs to be driven positive and negative. An audio amp is one example where you need to drive power both directions.

The wire feeder just drives the output positive, so onlty the 35 is used.

You can't use a TIP36C for the reasons Scott has given.

There are also TIP35, TIP35A and TIP35B. these all have lower voltage ratings than the TIP35C fitted originally and shouldn't be used.

Probably the least troublesome way to get one or two TIP35C is to look on ebay, which can be quite good for components.


BD249C is a substitute, but unless you happen to have one to hand use a TIP35C, which is what was fitted originally and is probably easier to get and cheaper.

Thanks for the reply folks.
DAMN AND BLAST IT .
Been on ebay and found a few that do components messaged 4 of them and DAMN AND BLAST not 1 has replied to me.So thinking I was been clever ordered a 36c,what a numb nutz i am .
So if anyone knows someone that requires a TIP 36C darlington transistor I got one . A bargan at £3.49 which includes postage.

Anyway why cant I just mount it the other way round,I am so desperate to get the damn welder going again.

NPN and PNP are functionally like a right hand threaded bolt and a left hand threaded bolt.
Not something that will really interchange.

wotwot said:

Anyway why cant I just mount it the other way round,I am so desperate to get the damn welder going again.

Click to expand...

Because a transistor (or radio valve, or thyristor etc) of a particular type needs to be set up with a specific set of electrical conditions to work, and if different conditions are applied it will either sit there doing nothing or be destroyed. The conditions for an NPN transistor are completely different from those for a PNP transistor.

Thats what i thought when I read shenions reply.
Wish I had the funds to buy a new one as mine is approx 15 or so years old.
Even though it owes me nothing and has been super reliable I would like to get it working just to finish the job on my vw camper.
The wire feed mechanism on my migmate is all metal construction with a windscreen wiper motor for drive.
I would hate to buy a newer model with flimsy plastic wire feed system.

Well if you buy the correct transistor, you have a fighting chance of getting the SIP to work, although there just might be more to it than a dead transistor, such as another fault which has caused the transistor to die.

If you get it to work you can finish the camper van and if you want a new MIG set, you have a working set you can sell to put towards the price. Much better than trying to sell the SIP for spares or repairs. Well worth a few quid and a few hours of effort.

PTvor the only other fault with the migmate is ME I'm the numb nutz that dropped the torch onto it in the first place,I'm 99% sure thats the only fault with it now as the only thing that does not work is speed control on the wire feed.
It welds but much to quick for me to keep up .

JOY and RELIEF the welder is up and running like a dream ,thanks for the replies and links.
And a big thanks to the tech team at RAPID in colchester for helping me out with parts.
Only required the tip35c darlington resistor a zenor diode a resistor and a little soldering.
I replaced the potentiometer (wire feed dial) just to make it easier to turn the dial as it had been broken a couple of times and was difficult to turn at times.
So a total cost of £15 which includes diesel money to go to colchester and back.
This is a big relief to me not to have to pay out £250 (approx) for a new machine.
Hope you dont mind the link mods but may come in useful to others, they have a sales counter you can actually go to and buy bits .
http://www.rapidonline.com

Good to hear. Those old machines are worth keeping going.

Should keep you going for another decade

BTW, I was wrong, it is a regular transistor, not a darlington. Most of the TIPxx parts I have used were darlington so made a wrong assumption.

Hmm, I think a darlington would work better.

I think your right on the old machines, even sip used to make them much stronger back then,will take a photo and post it up as it seems quite a rare well built sip .
Managed to get the tip35c for £3.40,not cheap but alot cheaper than a new machine,
still trying to sell the tip36c.
Think I might treat it to its first new liner,are there any preffered brands or is any ok.