Plasma Cutter Giant Tools LGK-60 not working

[petehall347]

Re: Plasma Cutter Giant Tools LGK-60 not working

sorry no idea .. i have a neighbour that fixes them but cant use them so he pays me to to do the work with the machines . . thinking about it there must be high voltages needed and be driven by certain frequencies ,

[sam_sam_sam]

Re: Plasma Cutter Giant Tools LGK-60 not working

What is the part number of IC 1 in the photo that you have posted

Do it have any optic sensor on any of the boards and have you checked them


Have you checked if the IGBT module is getting the command power signal to turn on

[CapLeaker]

Re: Plasma Cutter Giant Tools LGK-60 not working

sorry no idea .. i have a neighbour that fixes them but cant use them so he pays me to to do the work with the machines . . thinking about it there must be high voltages needed and be driven by certain frequencies ,

Umm, no... the other way around. AC is converted to DC, then the DC is converted back to low voltage, high current AC. PWM is good to 500khz so I am guessing they run around 250khz.

What is the part number of IC 1 in the photo that you have posted

Do it have any optic sensor on any of the boards and have you checked them


Have you checked if the IGBT module is getting the command power signal to turn on

That is the control module or where everything is starting to happen. There is a small PSU, IC1 is a UC3843 PWM, then there is this massive gate driving circuit. I am thinking in order for the arc board to turn on, the inverter has to be running as well. I've checked what I could on this controller board, but didn't find anything that sticks out.
On top of the inverter board to the far right are 2 connectors. The smaller one with the 2 red cables coming out go to the arc board and gets switched by the black relay. From there it goes through the transformer and through bunch of arc circuitry, that spark gap and the 2 output lugs XS1 and 2.

I still haven't figured out how this controller board gets enabled or turned on.

[sam_sam_sam]

Re: Plasma Cutter Giant Tools LGK-60 not working

Umm, no... the other way around. AC is converted to DC, then the DC is converted back to low voltage, high current AC. PWM is good to 500khz so I am guessing they run around 250khz.

[LIST]
That is the control module or where everything is starting to happen. There is a small PSU, IC1 is a UC3843 PWM,

Do you think IC1 is working I seen this type of chip go bad in servo controller before if this chip does not cost much I would recommend replacing it

then there is this massive gate driving circuit. I am thinking in order for the arc board to turn on, the inverter has to be running as well. I've checked what I could on this controller board, but didn't find anything that sticks out.
On top of the inverter board to the far right are 2 connectors. The smaller one with the 2 red cables coming out go to the arc board and gets switched by the black relay. From there it goes through the transformer and through bunch of arc circuitry, that spark gap and the 2 output lugs XS1 and 2.

I still haven't figured out how this controller board gets enabled or turned on.

What is the part number for the IC chip that has a ( #6 ) on it
I thinking that this chip might be controlling the power on command if it is some type of micro controller

Can you show this part of the circuit ( arc circuitry ) board if you can

Also some do you get any type of arc at all when you push the button to weld

[CapLeaker]

Re: Plasma Cutter Giant Tools LGK-60 not working

On the last pic that 16pin IC (I think it is a KA3525A For some reason it also could be 9535 or a 8535, hard to tell) is the PWM that drives a couple of predrivers (them 4 TO-220 packages). While there aren't any shorts, them two gate drivers measure a bit different on the 16pin IC (compared from one to the other).

There is absolutely no arc at all, if I press the button, all that happens is I get air.

[petehall347]

Re: Plasma Cutter Giant Tools LGK-60 not working

is there a sensor that checks air pressure before arc can happen ? just a thought like .

[CapLeaker]

Re: Plasma Cutter Giant Tools LGK-60 not working

is there a sensor that checks air pressure before arc can happen ? just a thought like .

This one doesn't have that feature. It only has the air valve. There are also no extra little gimmicks in the wand that disables the machine, if the head is off or something like that.

[sam_sam_sam]

Re: Plasma Cutter Giant Tools LGK-60 not working

On the last pic that 16pin IC (I think it is a KA3525A For some reason it also could be 9535 or a 8535, hard to tell) is the PWM that drives a couple of predrivers (them 4 TO-220 packages). While there aren't any shorts, them two gate drivers measure a bit different on the 16pin IC (compared from one to the other).

There is absolutely no arc at all, if I press the button, all that happens is I get air.

I would replace the PWM IC chip and see what happens did you check the ( 4 TO-220 devices to see they all the same exact reading

[CapLeaker]

Re: Plasma Cutter Giant Tools LGK-60 not working

Well, I did put that thing back together and did more measurements. I have 345V DC going to the inverter board, so the PSU is O.K, but nothing coming out from the inverter when keyed up.
However there is just one plug that goes from the control board to the inverter board and the wires are red, black, green and green. If I unplug the control board from the inverter board, I measure a short of 8 ohms between the red and black wire at the inverter side.
The control board side measures 680 Ohms between red and black.
On the picture them red and black wires go to that little transformer underneath those 4 wires. O.k. maybe there should be AC on it and I got nothing.
Left of that little transformer there are 4 black and 4 red wires. Those come from the PSU and provide the 345VDC. That red side is going to BOTH lugs of that little transformer on the left side If I measure between that, I get 2 ohms resistance.
The black and red wire from the 4 pin port go to the right side of the transformer. That is where the 8 Ohms short comes from.
If I measure DC between either black and red to either of the green wires, I get 25.8VDC untriggered and 25.3VDC when I trigger that wand. I am pretty sure the inverter isn't getting keyed up. No output of the inverter, there wont be any sparks.
I've tried every AC / DC measurement combination available on the red, black, green, green wire to see if there is a some clear signal that triggers the inverter on and didn't find any. Bummer.

[CapLeaker]

Re: Plasma Cutter Giant Tools LGK-60 not working

I am going to order replacements for all 3 IC's, on the control board and see whats happening...
The two green wires go to the PWM pre drivers, the black is GND and the red one goes also to that little vertical pcb on the control board.

[CapLeaker]

Re: Plasma Cutter Giant Tools LGK-60 not working

Well guys and gals... The plasma cutter is FIXED! The last problem was that the control board didn't get the signal to turn on.

Besides the bad main filter capacitors, the trouble was actually on the arc board. The turn on signal was there for the air valve, but not for the controller board to turn on the inverter. I chased things around on the arc board and found 2 bad 22k resistors R6 and R15. R6 was way out and R15 was out of spec. Changed them out (look at the brown resistors) put it back together and I got 465V AC from the inverter, but no arc. Adjusted the spark gap FDQ to roughly 1.25 to 1.50mm and low and behold I've got the arc going in between them plates. Finally that case is closed and that stupid thing isn't smarter me.

This fix is for those that have the air valve go, but no AC voltage coming out of the inverter board when keyed. So there will be absolutely no spark from the wand, acts like dead.

On the arc board the trigger goes to CN5 (blue and green wire). The turn on signal for the controller board is on CN4 (the one on the right to CN5) and has a red, blue, green wire.
Between that blue and green wire should be 5V DC going to the controller board when triggered.

[sam_sam_sam]

Re: Plasma Cutter Giant Tools LGK-60 not working

Good work

I am glad you finally figured out why it was not working

Save it from the land fill

[CapLeaker]

Re: Plasma Cutter Giant Tools LGK-60 not working

yeah... had to wait for things to warm up around here. I didn't like working in the cold garage. Actually, once one figures a plasma cutter out how things work inside, it isn't that bad. Of course a schematic would have been helpful, but that's waaay to easy, hi.

[sam_sam_sam]

Re: Plasma Cutter Giant Tools LGK-60 not working

Actually, once one figures a plasma cutter out how things work inside, it isn't that bad.

This is half the battle is understanding how it works and how the controls work

Of course a schematic would have been helpful, but that's waaay to easy, hi.

It would be easier

but most of the time there are no schematic
or
they are not complete only certain part
or
they are function block diagrams

[CapLeaker]

Re: Plasma Cutter Giant Tools LGK-60 not working

BTW, I've heard back from that guy today. He was saying that this plasma cutter never worked so good like it does now. Made my evening!

[sam_sam_sam]

Re: Plasma Cutter Giant Tools LGK-60 not working

Yes sir

that is what is important

I like that kind of feedback

[RickYuke]

Re: Plasma Cutter Giant Tools LGK-60 not working

Read with great interest your posts on this. I too have the same unit same problem, though the caps don't looked cooked like yours. My question you mentioned that the cutter was hooked up wrong, wondering what was meant by than, my unite is a 220V set-up. Thanks

[CapLeaker]

Re: Plasma Cutter Giant Tools LGK-60 not working

Someone had put a different plug on the cable and was wired up wrong.

[sam_sam_sam]

Re: Plasma Cutter Giant Tools LGK-60 not working

Someone had put a different plug on the cable and was wired up wrong.

What the power in cable if so why was it marked to the way it suppose to be hook up

If not the main power in

What cable was hooked up wrong

[CapLeaker]

Re: Plasma Cutter Giant Tools LGK-60 not working

The story I've got told was that someone had cut the plug of the power cord and put a different plug on it, randomly hooking up the 3 wires. However, this was corrected but the unit didn't work anymore and came to me. Surely there was a different plug on the cord.