Spectrum 187 Plasma Cutter

[jjohn76]

That gold bar is a resistor and together they sound like the RC snubber across your output rectifier. Did your original output rectifier test ok?

[mmurray39]

Yes think so numbers a little low think it was .oo9 . but hay we may have a breackthrough under lem unit there's a blue oblong. Thick film thing it does ent show current flow all others do. Might this be the prob ??? Got some coming but to actually find it ??

[jjohn76]

.009 is pretty low, that's a good indicator it was shorting out. Usually film caps tend to swell or show they've gone. When you measure them for resistance, you'll typically watch the go from low resistance to very high resistance.

[jjohn76]

That capacitor looks like it's ok to me. What happens when you measure it out of circuit? The biggest challenge with measuring them in circuit is you're usually measuring capacitors in parallel with something else. So the current could be flowing through the other circuit in parallel.
Which way are you working on the board? It sounds like you're tracing the power flow from the transformer output through the torch and work clamp.

[mmurray39]

Yup I'm doing it backwards ain't I ground it pos. K. The poly capasitor had no readings either way there are 3 more acted kinda like diode an capasitor started high down to zero this one nothing 3 bucks Are they umm polarized a plus side the lem units in nawalk packaging 2 for 20 there a pain to get out tried the horse shoe heat up modified the Weller. Worked well

[jjohn76]

The one up above showed a 250VAC rating, so it works in AC circuits - not polarized. Depending on your multimeter and what's in parallel the circuit, the resistance across a capacitor can say a lot of things. They eventually read whatever is in parallel with them, so if the resistance goes to zero, there may be a shorted component (snubber diode?) in parallel.

What's going on with the Hall sensor (LEM)?

[mmurray39]

The lem was just i was there rember the ole Chrysler hall effect ignition $20for2. Been everywhere else not a fan of the board construction. Lol. Having thoughts. 2 mo ago plug it in now sorta sorta prob wrong might know nothing there's newer diffrent stuff doing same thing and we get a new chip production plant just around corner the patent owned by millerweld are very interesting as to workings and goings on some smart boy there

[mmurray39]

Hey get today off gonna put new bits in now as most everything electronic(liking 43 max. Simplicity)if it had a stroke the brain chips i expect are programmed just for this or where they that far along back in 07. Thinking 256 computers where big umm o7so ill give it a go we will see checked the diode fees they check the 1 2 pole took it out the other 2 the s to d to g an back over seemed to be pretty close octicoupler seems to be alright. Not lookin forward to playing with the big electric lol

[jjohn76]

I can't remember if there are one or two micro-controllers on that board, but they're programmed on chip and very likely only for that machine.

[mmurray39]

Great

[mmurray39]

Doing um. All there are 1 big log 3 mimi loge look more like analog prob not nowhere near today's superchips still slugging away death in.famaly thurs blew that day up owe well just sluggin

[jjohn76]

Are all of those components bad? Did you pull for LA8040 off the heatsink? Was the 7805 on a heatsink? If the 7805 is bad, chances are the micro-controller (looks like U1). Is that upper right component Q5? It's hard to believe the unit would still do anything at all with that many components bad.

[mmurray39]

No pulled to check hey is this a zero ohm or 10 ohm resistor. There except for the diode one of two legs missing anyway

[jjohn76]

That's a zero ohm resistor. It's worth downloading the datasheet and seeing if those components are still available before pulling them. Many are no longer available.

[mmurray39]

Kinda thought so seen 1 for $ 1200 thought they where crazy waiting on parts hanging in there