Iskravar Mig 250/4 - auxiliary transformer

Nix2 · 2026-02-03T09:09:32+0000

Hello
I need a replacement auxiliary transformer for an Iskravar Mig 250/4 semi-automatic welding machine (made in Slovenia).
The original is an ELMA TT 470-050-136( prim. 230/400V, sec. 24/42V).

I want to replace it with an Esab transformer EuTs 013 rated for 27V (with a resistor selected if necessary)/42V.

The problem is that I don't know what current is required for 42V. The board is a VAR 17. Does anyone have a schematic/power supply data for the board?

Regards

eddie49 · 2026-02-03T11:57:50+0000

That board has probably got 3 SCRs and with the two large diodes provides a braked, half-controlled bridge rectifier.
It is also known as RE174B, used in Murex:

Pardon our interruption...

and Butters AMT 271:

https://www.mig-welding.co.uk/forum/media/albums/spare-pcb-a-for-butters-amt-271-mig-welder.155/

S

Thread 'Butters AMT271 a bit of help needed'

Oct 30, 2016

Hi, as per title I have butters welder, bought it couple of weeks ago with suspected pcb problem. When I checked the welder I found out that mode(function) switch is a bit knackered and someone tried to fix it as all wires going to it were cut then soldered back. I bought and fitted new switch ( about £3 from maplin) but don't want to try machine until I find out which way plugs are connected to pcb. It surprised me when I discovered that they haven't got any locating pin or other device, you can literally unplug them turn 180 degrees and plug in back, what's more you can swap them and...

Also a Hobart:

T

Thread 'Hi From the Highlands'

Mar 7, 2020

Hi all
New on here and looking for a bit of help.
I have a Hobart BetaMig 300 K1 mig welder that has worked trouble free for many years but has started playing up. It would not fire up at all ,took the covers off and discovered a small glass fuse (2.1A) had blown. I replaced it but it just keeps blowing,you can see the cooling fans just try to start up but then the fuse goes.Tried completley disconnecting the torch but made no difference.The fuse is not actually on the board itself but on a seperate fuse holder.
Has anybody got any ideas?

Thanks

The board is pictured in Post #14 there, and the auxiliary transformer is discussed in Posts number 15 and 17.
The wirefeed motor, the gas valve, and/or the contactor could use 42 volts, but maybe nothing does, and it is just there to potentially supply a 42v CO2 gas heater...?

Nix2 · 2026-02-03T13:39:22+0000

Yes, the board looks very similar (at a glance) to mine, except mine is a VAR 17, while this one is an RE174 (B).
But is 42V only needed to power the gas heater?
According to the data here (it looks like the board manufacturer) the board is powered by 42V, and again, in my diagram below from a similar machine (Iskravar 300), there are two power supplies per board, 24V and 42V...

https://www.re-elettronica.it/files/acatalog1/download/re174.pdf

eddie49 · 2026-02-03T19:31:05+0000

This type of board when used in Butters welders has been discussed here:

P

Thread 'Butters AMT 311'

Nov 2, 2025

Hi all,is there any one person on this planet that would have, or access to a circuit board diagram or any form of schematics, so I can try and fault find the problem I'm having. Whenever you turn the welder on the gas starts to come through,and continues to keep coming through until you turn the machine off.while you are using the welder the gas solinoid cuts off and comes back on whenever it feels like it,I've tried looking for information on this machine but can not find a single thing(, and have I tried looking) I would have to say this is the best mig I've ever had.Any ideas would be...

and here:

P

Thread 'Butters AMT 311'

Nov 16, 2025

I would like to thank anyone who has tried to help with the problem I'm having with my welder,everything else on the machine works great apart from the gas solinoidseems to be energised most of the time,I have to keep turning the machine on and off all the time,so I don't waste gas,I've already run one gas bottle off without realising it,and at great cost.it a case of tracing the two gas solinoid wires back as far as possible to find out why they are always live? The only time the gas stops is when I turn the machine off,then as soon as I turn it on the gas is coming through the nozzle...

The RE419 version referred to in those two threads seems to be available in two single-supply versions, one for 24v and one for 42v, connected to Pins 1 and 2. However your diagram above shows that the RE174 version appears to need two supplies, with 42v on Pin 2 and 24v on Pin 13.

* It is possible that the 42v may only be used on the board if the Contactor ( K1 in your Iskravar 300 diagram ) has a 42 volt coil.

Those two Butters threads link to an Italian website "www.re-elettronica.it/files/acatalog1/download/......".
I tried replacing the final "re419.pdf" with "re174.pdf" and got this:

https://www.re-elettronica.it/files/acatalog1/download/re174.pdf

Note that it is for "174" not "174B".
That document states that it uses a single supply, which is 42 volts. So now I don't know what is correct ...!