Figuring out the electronics on a wire feed unit

[penfold]

Are there any markings on the big blue thing with the wire wrapped around it or the 8 legged black thing that's been glued in with a glue gun?

 

[mike 109444]

The use of a center taped transformer won't have much to do with the rectifying as a non center taped transformer will also allow for rectifying. Your description of the toroidal is that it only has 3 wires, is that all are there no other wires as in a secondary winding if not then if I recall it will be used as an auto transformer. I would say that the small pcb's job is to provide a logic voltage supply to the display/controller pcb (12v) and also to take the output from the display/controller pcb via the ribbon cable to send control signals to the main power/welder unit via the bunch of blue wires going to the multi pin plug on rear panel as this has to tell the main unit to up or down the power. Therefore main unit may not have had the usual rotary type power selection switches. As the display pcb has the DC supply out to the motor (plus gas valve) I can't see where the DC into the display is?

 

[mike 109444]

Are there any markings on the big blue thing with the wire wrapped around it or the 8 legged black thing that's been glued in with a glue gun?

Think you will find that the blue thing is an inductor (iron ring/loop) to soak up any interference. The black device on it's back! looks to be a relay, and judging by the addition of the wires underneath it's the wrong one hence being up side down and jumpers being used. (bodge repair )

 

[Bill Edwards]

The big blue thing with wire wrapped round has 'LA 55-P/SP1' and '12085'. What is it?
The black thing has '0.5A 125VAC', '0.2A 110VDC', '1A 24VDC'. Also '21 Z9 N4' and the pins which aren't covered in glue are 4, 6, 11 and 13. It has a diode across two terminals where two wires are connected, and it appears to be a relay.

 

[Bill Edwards]

I think the supply to the PCB with the display has to be via the ribbon wire as this is the only place remaining when you remove the gas solenoid, wire inch and torch trigger.

 

[Bill Edwards]

If the output from the small (40 to 13v) transformer goes through a rectifier would an easy test be to simply connect 12v to it (via the blue wires)? Surely the polarity couldn't be wrong as it'd be before the rectifier and it would power up the 12v side of things? Mind, I can't see a rectifier myself unless I'm missing something.

Ah, having just followed the blue wires onto the board it connects to the little roundish black device next to the plug which has 'W04G' and '140C' plus a couple of squiggles that indicate AC. It also has 4 contacts, leaving me thinking it is a bridge rectifier?

 

[mike 109444]

If the output from the small (40 to 13v) transformer goes through a rectifier would an easy test be to simply connect 12v to it (via the blue wires)? Surely the polarity couldn't be wrong as it'd be before the rectifier and it would power up the 12v side of things? Mind, I can't see a rectifier myself unless I'm missing something.

Ah, having just followed the blue wires onto the board it connects to the little roundish black device next to the plug which has 'W04G' and '140C' plus a couple of squiggles that indicate AC. It also has 4 contacts, leaving me thinking it is a bridge rectifier?

Yep

 

[Bill Edwards]

So, connecting 12VDC to the AC side of the rectifier would be a safe and easy way to see if anything lights up.

 

[Bill Edwards]

Well I put 12VDC power to the AC input for the rectifier and...
The unit lit up! I had both displays on and could adjust the amperage using the knob (up to 300 ), though nothing else - no wire feed control and some kind of error on that display, presumably because it hasn't any connection to a welder.

 

[Robotstar5]

Well at least it looks impressive even if it does nothing else

 

[Bill Edwards]

Yes, I think that is a good assessment. Without understanding exactly how it connects to the welder I don't know if it will be of any use. I suppose I could continue with the idea of just getting a 40ish V supply and a PWM controller for the motor but connect the low voltage side too so it looks all fancy!

 

[penfold]

Try shorting the torch trigger feed; perhaps the wire feed might come to life?

 

[Bill Edwards]

OK, I've been able to return to this.
I can't get the wire feed motor to operate. The inch button doesn't operate it, nor does shorting the two connections for the torch. It operates the gas solenoid though, just not the wire...

Having had a fiddle I can use the interface. It seems you can program it for different jobs which it presumably saves so you can keep your favorite settings. It can be set to keep the gas on for 1 or 2 seconds after you release the trigger for a little post flow, which I quite like the sound of.
The wire feed control is from 0 to 20 in increments of 0.1. I must admit that, although I was on the verge of just using the motor mechanism connected to a PWM controller (I was ready to order the bits), having the very fine control offered by the onboard circuitry would be great.
Any thought on what I need to do to get it to work? What element is missing for it to send a signal to the wire feed?
Does it want to see there is voltage available for welding, it has sensor(s) on the welding lead? Surely the inch button should make it work regardless of anything else though?

 

[penfold]

Some better pics of the PCB behind the control panel are needed; I need a look at that, there must be something on there that controls the feed motor.

 

[mike 109444]

I would still find it surprising that the power for the wire feed goes up the ribbon cable then down those thicker cables. i know they could be using several of the cables in the ribbon but would find that poor practice.There is a connector that is not connected on the psu pcb and also one on the display that looks like it has the same number of connections.

 

[Bill Edwards]

I too would find it strange - but there aren't any other wires it can be.
The unused connector on the psu pcb is actually the power to and from the small transformer, it was simply disconnected to allow for better less bad photographs. The one on the display board is an 8 pin, I'll try to take it all apart enough for some more photos.

 

[Bill Edwards]

This is one side of it:


To have any hope of reaching the other side I need a very small socket so it'll probably have to wait, I should be able to come back to it tomorrow.


The 5 pin connector on the bottom right, just above the green connection is unused. The smaller one at the top is the 8 pin one that is also unused, as seen in the other photos. When I can get the board out to reach the other side I'll try to get some non blurry photos.

 

[penfold]

What an absurd design. Have you tried the wire feed motor to see what the current draw is?

 

[Bill Edwards]

No, not yet. I don't have a 40VDC supply to test it at its full speed, plus without having wire and a torch I'd have to then take a guess as to how much extra it would draw when under load.

 

[the snooper]

if both machines have the same transformer you can wire them is series to connect to 240 volts