Need some help with a power master 256

[Tallguy64]

Hey all,

I got a oldie but goodie pm256 this is more for technical help then anything. It has been working great up till a couple days ago when I was cleaning off the plasma table scraps and it decided to die out. I thought it might be arc gap so I opened her up and they were a little dirty cleaned her up fired it up with the case of and no pilot arc. I can see it arcing across the points but after a few seconds it thought the red light on the front. I have tested the stick and tie and they are both working but no plasma. I found what looks like a burnt out resistor. It is labeled 15 2r7. Any idea what the resistance is supposed to be and or is it possible to get a replacement bored for this unit still?

[Blaster]

Yea,,, you know that's Not the way it works ~ right

That resistor is very unlikely to be the Problem, but rather the the Result. Change it and, chances are, the new one just overheats again...

"Visual Electronic Repair" is pretty nonexistent!

[christian]

Yeah,

But why not try treating the so-called symptom first?

I mean, soldering in a 25 cent resistor is a quick and easy process that would be worth a shot, to me.

Sure, it probably does equate to "visual electronic repair", but maybe he'll get lucky.

[Blaster]

Naaa...

So let's hope that the resistor is now OPEN and unable to pass current. Typically, there is something downstream that's shorted-to-ground and forcing that resistor to carry many times it's rating. It acted, although unintentionally, as a Fuse.

So, you want to reapply that short in hopes of "getting lucky"

Not a good plan...

Getting lucky would to be able to visually trace the circuit involved with that resistor, see what it's purpose it and recognize another component as the likely culprit (otherwise you're going to need to dig-up a schematic). Either way, just like with welding, you really have to have the experience to proceed.

[christian]

Yeah,

I'm no electronics tech, so I'm no whiz with a multimeter.

But if a newly fitted resistor blew again, it probably would do any new harm and you'd just be back to the same so-called spot. But that's just my logic, which may not necessarily follow with circuit boards.

Otherwise, I get the impression that the unit is older and out-of-warrantee. However, Everlast may still be able to provide a board like that at a reasonable cost, even out-of warrantee.

His Stick and TIG both still work, which is something. But he says he was cleaning the Plasma table before the Plasma cutter portion failed, so maybe he just blew some metal particles into the unit, which could have shorted-out a daughterboard, i.e., no inherent problem up or downstream, necessarily.

Been there, done that, with a cheapo CTS 416 that was first, and pretty cool TIG/Plasma/Stick little combo unit that looked like the one below. I got a CAT520 right after that and was more cautious about using an air compressor to clean areas off near welding units. That CAT520 served me well for years, until I traded it away to a friend for some tree trimming service.



Anyway, hopefully the OP will have some luck and will let us all know what happens.

[Tallguy64]

So i use this unit to cut up the scraps from plasma cutting off the table. This machine has been used and abused.... A LOT. This unit was one that originally had an improper spark gap set. Fixed that. Then used it for a bit on said plasma table.... then upgraded the plasma stable with a heavy duty dedicated unit. Now it is used as to clean up the scraps of 4x8 sheets so it can be recycled easier. That being said when i opened it up this time i found the pilot arc wire loose on the inside not sure if this can have a bad reaction on the resistor or not but i fixed that and like i said found that resistor like that. Is is on a little break out board off the main unit that looks like it has to do with the plasma side. The pilot arc wire runs to a small board then from that board there is two wires that run to this board with the blown resistor. If i had to guess the first board is for sensing arc creation and this board controls that. Not sure. Didn't have time to call into technical today to see if they could help out.

I realize that there is probably a reason it melted down not sure if it was the loose wire but why not replace the obviously broken part and go from there. I will be removing it to ohm it out just didn't have a chance yet as my buddy has my nice soldering iron.