Retrofitting pedal

[MrFluffy]

Hi, Im happy with my lovely old BOC tig mostly, but I could see a pedal making life a lot easier on thin stuff when the weld pool gets a bit hot to be able to just lift off would be a definite advantage.
Now, I have no socket on the front of this tig for a foot pedal and no setting on the mode selector for one either, but the lead trailing away from the socket below has a thinner gauge grey wire joined by a connector that looks like someone had something inline in a previous application, and its miles longer than the other wires too, suggesting it went off somewhere.
Is it likely this is where someone had cut in a pedal? or does anyone know what the pedal for this model of welder should look like/connect?
Theres no power controls on the torch either, just a on off switch.
Socket :-

Welder, theres so many leads as it has a watercooling unit inside too.

 

[shenion]

If you have a schematic of the welder it would help on wiring a pedal.

 

[MrFluffy]

I dont I'm afraid, it was a struggle to get the right consumables its been NLA for so long...

I should add that there was a second welder the same model but with a pedal bought by someone else before me, but the seller did not have any information how that was connected up...

 

[shenion]

The problem with older units is the foot controls are machine-specific. My Airco needs a 25-ohm, 150 watt rheostat. Dialarcs use 1000 ohm, 25 watt rheostats. You need to match the resistance and power handling to the unit.

Modern units are easy as they are electronic and the power control is low power.

If you open up the unit and look at the current setting control, you could get an idea of what it needs. Then you would need to ohm out the connections.

Best option is to keep an eye on ebay. I finally got a Miller RFCS-23A pedal. Old, beat up, but it works fine and has that huge power rheostat in it.

 

[Wozzaaah]

I can't find a schematic for your 375 but I'd assume the connections would be the same on similar models? If so you can download manuals for some of the older models from http://www.murexwelding.co.uk/

here's a murex foot pedal if it's any help

 

[MrFluffy]

Hmm woz thanks, thats very interesting...

It has the same plug style, and appears to replace completely the torch connection so I guess its possible the foot pedal replaces the torch on/off switch completely.

Which in this picture I just found of a pedal equipped unit, appears to be exactly how it is done...

Ill have a deeper look at it in a bit...

 

[Wozzaaah]

If you could get a plug from somewhere you'd be ok. You can buy a bare pedal with no plugs for around £195 or you could make one, shenion did a while ago

 

[MrFluffy]

Ah bonus, B&D are wired to the switch on the torch, and i can reuse the plug I have already!
Now I wonder what wattage the pot has to be...

 

[shenion]

If it is 10k, the probably any pot will do.

 

[lovelectricity]

sorry mrfluffy i just gotta come in. is the jerry can in front of it, incase it doesnt work? i like it a case of you will work, or you know what im going to do to you. my car recently got promised, if it passed mot, it could have some new spark plugs. sorry again i seem to have a leaky think tank.

 

[tigmann]

Looking at the pic of the machine connector it seems it is fitted with
an Amphenol type socket so you will need the corresponding plug
to connect in to it.
You wil also need the "pinout" connections to be able to wire it up
properly which should be available from the Murex website in the
"contact us" section. they have a number of different technicians
who specialise in the different types of their welding machines.
I have no doubt they can supply the correct plug for the job at a
price which won't be cheap!
Other footpedals may do the job ok depending on whether the wiring
is a 2 or 3 wire system.

 

[MrFluffy]

I have the plug already as per earlier post, since thats how my torch connects, it appears to use the posted wiring diagram too handily

Ive bought on a tig foot pedal with a 47K pot inside that should do the jobbie but was LOTS cheaper than 200 notes...

Thanks all, just got to wait for the foot now

 

[graffian]

Not sure if your sorted.
The foot pedal is really simple.

First thing it does is hit a microswitch. An old jag inhibitor switch works, I have one wired with speaker cable to a jack on my foot pedel for when I am tangled up in work and can't get to a pedal. This is connected to the two pin socket thats down in the right hand corner on the later square wave.

Then it needs two pots for current control, if you want current control. The machine puts out something like 15 volts and the current control divides it and puts the voltage onto PCB 1[later square wave] to control the current. One pot has a knob on the outside to set max current. The other is a slider pot and is connected to the pedal so it's like a throttle.

I can give you the values of the pots if you want, they are not critical, I think they are around 50K. The main thing is durability. I have replaced the bloody slider one about five times.

The wiring of the pedal is on circuit diagrams usually.