SIP Ideal 120 Blowing panel fuse

[Licker]

Good afternoon,

I have the good (?) fortune to own a MIG welder that is nearly as old as me, and with the exception of renewing the torch every couple of years it has given me faultless service for years, until a couple of days ago.

Mid-weld it just stopped and paying a bit of attention shows that it has blown the little 5A glass fuse mounted on the control panel. Replacing the fuse restores the light, but as soon as the trigger is pulled the fuse pops again instantly (before any clunky clunky relay sounds or wire/gas being fed). Spent a while searching for similar issues with no real success (other than it may be the rectifier/PCB/feed roller) so it's time to beg for advice.

I've pulled the torch apart to check the contacts and tried it with no wire in and the feed roller undone, both with the same result. Pulled the control box out and looked for any signs of burnt out pcb (long shot I know) and dropped the side of the MIG to check inside for any loose wires, so now I'm at the point of staring at it and sucking my teeth like a builder who's about to give you his estimate

Can anyone point me in some kind of 'do this,test that' way forward please?

Luv n hugs

 

[rtbcomp]

Welcome to the forum.

If the fuse blows before the contactor pulls in it could be a faulty contactor.

I'd try disconnecting one of the wires going to the contactor coil and see if that makes a difference.

Usual safety precautions apply!

 

[mike 109444]

In a similar thought to rtbcomp Try unpluging both the wire feed motor connectors and the gas valve connectors (use tape to stop the wires shorting out on any thing) If now the fuse still blows when trigger is pressed then again could be contactor or the pcb that feeds power to feed motor and gas valve. If fuse does not blow then try reconnecting the gas valve first (least likely to be at fault) Now again try trigger again. if fuse still ok then reconnect feed motor, if now fuse blows could be duff motor or the pcb that drives it. Please report back on findings.

 

[the snooper]

also if you have a multimeter test the relays and so on for a dead short its cheaper then going through fuses

 

[Licker]

Wow, thanks for the replies people :-)

Here's a pic with numbered bits, in case I get owt wrong name-wise, so you can tell me I'm being a plank! So armed with a bag of fuses, I've been pulling wires with the following results:

[/IMG]
Pulled: Wire from contactor [1] to welding power level switch.
Pulled: Wire from contactor [1] to to big thing that looks like a transformer [3]
Pulled: 2 wires that go to wire feed motor [7]
Pulled: 2 wires that go to gas pump [6]

The fuse blew with the above disconnected (one bit at a time though). If I removed the live and neutral from the top of the contactor (one goes to control box and one goes to the main on/off switch) the 'on' light didn't illuminate anyway.

So, does this point to something bust in the control box on the PCB? Is it at all possible that a faulty torch could cause this (I've tested for continuity at the machine end and the trigger appears to be making/braking the circuit).

Any help, pointers etc muchly appreciated.
Cheers

 

[rtbcomp]

Can you locate the wires that go to the contactor coil and pull one of those?

 

[Licker]

I can if you could give me an idea of what a contactor coil looks like

 

[rtbcomp]

You've identified the contactor as #1 OK, the coil feed will be a pair of thinner wires, away from the rest, most likely those (black?) wires hidden behind the mains cable.

The coil is inside the contactor and provides the magnetic field to close the contacts.

 

[Licker]

OK...

On the contactor there are two sets of two wires mounted separately to the rest. 1 pair of white wires that end up at the gas pump and transformer? [2]. The other pair of black wires end up at the control box and the gas pump.

Unfortunately, disconnecting either pair, or indeed all 4 wires has no effect on the fuse blowing

 

[rtbcomp]

That rules out a shorted contactor coil then.

The "gas pump" is just a solenoid operated valve, not a pump.

 

[the snooper]

is it me or does the right lower terminal & wire look as though it has had heat damage

 

[Licker]

I see what you mean, however the insulation on that wire is the braided cotton type, rather than the usual plastic, and has dropped down the wire a bit.

There is however, continuity between the two lower red wire terminals - I'm guessing if that was meant to be the case they would have shared the same connector?

 

[the snooper]

its not the insulation that i noticed its the colour of the screw, there will be continuity between those red wires as its the primary winding for the welding transformer, disconnect the 2 brown wires at the top and connect them together with an insulated connector and try it again this way you are eliminating the mains switching side of the relay / contactor and the welding transformer

 

[the snooper]

a quick search produced this from another thread if yours is the same it doesnt look like the fuse it at mains voltage

 

[the snooper]

looks like you may have a part on the board gone and should be simple enough to repair

 

[Licker]

disconnect the 2 brown wires at the top and connect them together with an insulated connector and try it again this way you are eliminating the mains switching side of the relay / contactor and the welding transformer

OK, pulled the 2 brown wires off the contactor and joined them - fuse still blows.

Also tried moving the dubious looking wire (and its counterpart at the top) to an empty pair of connectors on the contactor - fuse still blows.

As for the wiring diagram (and being fairly clueless with such things) I'm not sure that it is the same as - if I am interpreting it correctly - there are 6 wires going into the pcb (if thats the box thing on the top right of the diagram) whereas on my unit there are 11.

 

[the snooper]

so that wiring diagram in of no use to you machine then

can you post a picture of your pcb

 

[mike 109444]

Licker the inside of your welder looks a lot like one of mine (a bora welder not sip!!)
The pic of yours I have added 8 and 9.
8 is the diode pack
9 is the cooling fan
and for ref
2 is the inductor (looks like a transformer) but is connected to the output of the diode pack then through the inductor and out to the earth clamp lead.

3 is the main transformer and takes the 240 (220 if it has a jumper strip) and dropes it to the lower voltages (selected by the power selector switch) to the power going into the diode pack then onto 2 ect..

4 is the low voltage transformer (probably about 24 to 30 v) takes the 240 and drops it to 24 to 30 for the various components via the pcb.

5 box containing pcb!

6 gas valve fed from the pcb item 5

7 feed motor feed from the pcb item 5.
Some of this you already know.
If your welder operates like mine then the fan item 9 only operates when the trigger is pressed so could be suspect as youor fuse blows when trigger is pressed. Try unplugging and testing.
Can't recall if the low voltage transformer is powered befor or after trigger pressing? I would guess that as it powers the pcb it is always powered?
Any way try fan 1st

 

[Licker]

Hi,

Not being electronics-minded (read: mostly clueless) that PCB diagram means nothing to me, but then again it's all a learning curve

Pic of PCB as requested - if it's rubbish or the wrong side etc. just let me know and I'll post up a better/more specific one.

Cheers

 

[Licker]

If your welder operates like mine then the fan item 9 only operates when the trigger is pressed so could be suspect as your fuse blows when trigger is pressed. Try unplugging and testing.

Hi Mike and thanks for the component info, great help and saves me referring to things as "that thing on the right near the doo-dah"

The fan on this one runs permanently as soon as the main power switch is turned on.

Cheers,
Lee