Arc-Tec 200A Single-phase MIG

Hi all,

I raised a thread in the 'Learning' section a while ago about using my little Clarke MIG for some 5mm plate welding on a narrowboat.

Having pushed it a little far against its duty cycle, leaving it smoking, decided it was time for an upgrade.

Picked a second-hand Arc-Tec 200A single-phase MIG up off the 'bay, for a small price. It came missing its Euro-torch and earth lead but I've got those on order, although having looked, the earth connection is marked 50/70, so that'd be a big one then?



















It seems in okay condition, and came attached to a 3P plug, running off 2P and E. I've wired it onto a domestic plug just to see if it powers up, which it does - and triggering the Euro connection starts the wire feed et al.

Any idea what indicators should be on, on the front? I'm assuming the remote motor is for an external wire feeder?

I can't find much info on the manufacturer, from Farnborough, so any ideas on whether it looks like a good find?

Cheers!

PC

Right, I've had time this eve to give this a go, to see if it actually works.

I'd ordered a Parweld MB25 Eurotorch, and an earth lead with the small dinse connector on it. Turned out the welder has a 50/70 connection, so I swapped that over onto the earth first:







Then I plugged it in, and gave it a go.

Firstly, I'd noticed when I tried it the other day, that the wire feed speed didn't seem to do much under 3/10 on the dial, and wasn't that fast at full speed, which may be a clue to the current problems!

The main symptoms are:

* Main contactor vibrates and won't fully engage unless held down with a screwdriver
* If the contactor is held down, then the actual welding current, at full power, is very low - like 'low' power on my old Clarke
* A big green Neon on the front panel doesn't light up - but it may not be supposed to - who knows?

I think, and I'd appreciate the advice, that this appears to be related to the odd info I was supplied with regarding the mains hookup.

The machine has a sticky label near the mains inlet saying "240v", then the main data plate in the first post above has figures for 240v and 415v.

I was told the 'electrician' for the person I'd bought it off, had wired it to work off two-phase, and it came with a three-phase plug with P1, P2 and E connected.

I've currently connected one phase wire to L, one to N and the E, to a three-pin plug for initial testing.

My suspicion is that I'm getting 1/2 or similar, of welding power and wire-speed power to the relevant components, because of the difference between P to P, against P to N.

Does that seem right?

It would seem to explain the contactor [24v coil] not pulling in fully, the slow wire-speed and the low welding output.

And the killer question - how do I change it to run on genuine single phase?

Is it a case of swapping a centre-tap on both 24v and main transformers back to the outer taps, or vice-versa?

I'll admit that my knowledge of 3P is pretty poor, limited to what I can remember from A-level physics a good few years ago!

So any thoughts would be appreciated.

One thing I have done is to check all the panel mounted fuses and they're all okay.

I've also tested the OCV, with the centre of the contact held engaged with a screwdriver (!), and got these results:

Both settings are 1-4, and if I try and weld with the contactor held engaged, it is capable (just) of melting 1mm wire.

Coarse------------Fine-------------OCV

1 1 8.6
2 1 10.2
3 1 12.5
4 1 15.9

1 4 8.2
2 4 9.7
3 4 11.8
4 4 15.0

Anyhow, some more pics to try and help:











Cheers!

PC

Hi all,

Feeling a bit like I'm talking myself through this - but I guess the thread might be helpful for anyone else with a similar welder...

I had the afternoon today to try and get this sorted.

Having had a think about the lack of both welding current, and the contactor not pulling in, I'd been relentlessly searching the forum for wiring diagrams to get a feel for how it was likely to be wired up.

Cleaning some of the dust off things inside, revealed these two slow-blow fuses on top of the 24v control transformer.



I swapped from the l/h (in picture) output to the r/h one, and low and behold, 24v at all things that should have had it! That fixed the contactor issue, and the wire feed speed, but not the main welding current.

I started tracing the contactor to power selectors to main transformer connections, but eventually got bored - although not without discovering something.

The contactor is a three-pole type, with connections for NC and NO.



There's only one thing using the NC one, which is the bleed resistor for the capacitor bank.

On the NO contacts, the two phase-lines come in, and there are three connections going out to the power selector switches. So one of these outputs wasn't doing anything.

I took a wild stab in the dark, and moved the phase-in connection from where it was, to the middle position. Hey presto - it worked and we appear to have full welding power.

I gave it a go on some 3mm box section:



First go above suggests there's power aplenty at least, given this is only running on a 13A plug.

A slightly more careful go managed this:



How does that look? Any good?

(Edited to add: That was with 1mm wire, and CO2, power on 3-1 so 75%ish, moving fast!)

It feels much, much better to use than the little Clarke - smooth with a lovely soft buzz to the arc. The wire speed is independent of power setting though, so it's a bit different to tune, and I've not played with the burnback control!

The only oddity I'm worrying about now, is to do with the OCV.

I've remeasured the OCV, and I'm getting the following readings - I've included figures recorded using AC and DC ranges on a very cheap multimeter.

Coarse - Fine - DC - AC

1 4 17.0 37.6
2 4 20.0 44.1
3 4 24.4 53.7
4 4 30.6 67.2

1 1 17.8
2 1 20.8
3 1 25.7
4 1 32.8

I'm a bit concerned that I'm seeing a large AC component on the output - isn't this supposed to be DC? I'd also be happy to suspect the meter, as this is a really 'orrible little one - must find the proper one!

Notice that the fine voltage control does little, and seemingly backward!
I've also tried the diode range on the two rectifier diodes, which appear to show they're a short in both directions. I didn't take them out of circuit to do that though - is that normal?

Anyhow, I'd appreciate your opinions on the above!

In the mean time, the little Clark looks a bit dwarfed by the new monster:





PC

Some of the really cheap little digital meters if on the AC scale, and fed DC, will give a reading, even when there is no AC.
Robert

Hi Robert,

Aye, I'm suspicious of the meter!

On the other hand, what do you make of the diode-range on the meter (and 0-200 ohm range) showing the rectifier diodes to be short circuit - is it typical to measure them in-circuit and expect a sensible result?

Cheers!

PC

The diodes will have capacitors and resistors across them, I would be surprised to get a decent reading while they are in circuit.
Robert

Ahha, thanks for that - that's my ignorance of how it's actually set-up showing...

I'll disconnect them and verify, just to keep me sane at least!

What would be the symptoms of either or both being S/C?

PC

If open, half or no voltage on the output leads with any sort of load.
If shorted, the transformer hums like it is under a large load and the line fuse will probably blow.
Your DC voltages look close to what would be expected.
You might try measuring the AC voltage with the meter leads red to pos and then red to neg, it might make the meter give a normal AC reading.
Robert

ive got the TIG version of this welder and never found any information on it although i did find a few of the migs for sale even that one although i forgot to bid on it
when i was down midland welding supplies the guy there knew a few things about these machines and i saw ARC-TEC written on a cabinet that they apear to keep manuals in.

where is the data plate on yours? mine has not got one.i always thought that mine was 32amp

gaz_moose said:

ive got the TIG version of this welder and never found any information on it although i did find a few of the migs for sale even that one although i forgot to bid on it
when i was down midland welding supplies the guy there knew a few things about these machines and i saw ARC-TEC written on a cabinet that they apear to keep manuals in.

where is the data plate on yours? mine has not got one.i always thought that mine was 32amp

Click to expand...

The data plate is just a sticker, on the rear of the machine - r/h side on mine...

Interesting about Midland Welding, I'll see if i can glean any more info from them.

The data plate shows 25A input at 200A output, at 24.5v OCV, but also shows an OCV max of 32v, which matches what I measured. I *think* that suggests more like a 300A maximum output, with the optimal arc length and wire speed. At that current, the input current will be up to 32A, yes.

At the boatyard, its running on a 16A type-C MCB, followed with 18M of 2.5mm arctic, then two 1.5mm 13A extension leads, and two 13A plugs on the welder - a (very) temporary solution whilst I rustle up some more 16A plugs/sockets. Yes, I know once one plug is plugged, the other is live...

Still impressed with the power and arc stability.

PC