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Welder Repairs, Yeah I Do That Too...

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Ulma Doctor

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I have a Powcon 300SS welder that stopped working last winter under mysterious circumstances.
the welder was sounding normal and during the middle of a pass, it quit working all together.
rather than fix it right on the spot, i took my other Powcon, a 200SM, off the shelf and use it in place of the 300SS for DC stick welding
i use my PowCon 200SM as the dedicated power supply for my FCAW (Flux Core) Rig, but it swaps out in less than 5 minutes.

I finally got a chance on Friday to repair the 300SS welder...
it got ugly inside....:confusion:

IMG_3157.jpgIMG_3158.jpg

IMG_3156.jpg
as you can see the Capacitor PCB Board blew up.

i had sourced a new old stock PCB from a nice fellow on Ebay, it was shipped fast and packed very well, i may add.

Then the fun began,
the board is held in place with screws and more than a dozen electrical connections that need to be put back exactly where they came from,
or you could fry the new board you are trying to replace! :confused 3:

the PowCon part number on the Capacitor PCB Board is 100220-001, for those looking to do the same job.

here is a picture of the 90% installed board assembly, it is wired up for 230V operation

IMG_3155.jpg

i reassembled the unit and reinstalled the covers for the test run.
i ran some 3/32 E6011 just for giggles.
the welder performs flawlessly.
if there is interest, i'll make a video of the welder and it's capabilities.

as always thanks for looking!
 

hman

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Durn! That board looked profoundly fried! Was the greenish discoloration on the upper left component (rectifier?) due to capacitor juice, or did something get wet 'way back when?

Anyway, congratulations on what looks like a difficult and persnickerty replacement.
 

Ulma Doctor

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Durn! That board looked profoundly fried! Was the greenish discoloration on the upper left component (rectifier?) due to capacitor juice, or did something get wet 'way back when?

Anyway, congratulations on what looks like a difficult and persnickerty replacement.
thank you hman!,
i think the greenish color was copper that has rusted since the blast.
the capacitors appear to be intact.
i don't ever remember the welder getting wet.
it may have been a loose connection that caused the problem, for all i know :fat:
 

Latinrascalrg1

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thank you hman!,
i think the greenish color was copper that has rusted since the blast.
the capacitors appear to be intact.
i don't ever remember the welder getting wet.
it may have been a loose connection that caused the problem, for all i know :fat:
Makes me wonder what the cause of failure actually was?
 

markba633csi

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Odd looking assembly; actually looks like those 4 components could be fast recovery rectifiers but who knows?
Good fix Mike
Mark
 

Ulma Doctor

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Makes me wonder what the cause of failure actually was?
i can only speculate, but here it goes.....
the nuts used to attach the 460v/230v bus bars to the PCB board are galvanized.

what i think happened, is that the nuts rusted over time.
the rust added to the circuit resistance on 2 separate poles on the PCB board. ( the other hardware on the board is all brass, except for these screws)
the resistance increased slowly over time and as a result the increased resistance generated more heat than the Board, and fan could dissipate.
but this is only speculation....
 
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Ulma Doctor

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Odd looking assembly; actually looks like those 4 components could be fast recovery rectifiers but who knows?
Good fix Mike
Mark
Thanks Mark,
you can't tell it by the pictures, but the big white packs are Capacitors.
all 4 capacitors have 8uF @400v rating stamped on them
 

FOMOGO

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Nice save. I've never had any of mine fail (knock wood), but if one did I sure would take a look. I have pulled the covers over the years and blown them out and checked connections. Mike
 

markba633csi

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Yep, I think your corrosion theory is correct Mike
Strange looking caps though, they must be special high current types, with the multiple lead wires and all
mark
 

Ulma Doctor

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Yep, I think your corrosion theory is correct Mike
Strange looking caps though, they must be special high current types, with the multiple lead wires and all
mark
thanks Mark :)
you are correct sir, strange they be, caps indeed.

Nice save. I've never had any of mine fail (knock wood), but if one did I sure would take a look. I have pulled the covers over the years and blown them out and checked connections. Mike
Hi Mike,
these PowCons are workhorses.
i was an Ironworker for a couple years when i was younger, i learned to love these little (65lb) bundles of sparks and joy.
you can kick the crap out of these things all day long and they keep welding.
for a short period of time i repaired the welders (in the company shop) because i opened my mouth and said that i was pretty good at fixing things.
well, they tested the statement and i'm still not sure who got the short end of the stick :cry:

what i experienced most was major blow ups due to morons plugging 230V machines into 460v,
even though it was clearly labeled on the welder in 4" letters 230v only :mad:
you can plug a 460v machine into 230v, it doesn't run but it doesn't cause the damage of the reverse.
 

Latinrascalrg1

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i can only speculate, but here it goes.....
the nuts used to attach the 460v/230v bus bars to the PCB board are galvanized.

what i think happened, is that the nuts rusted over time.
the rust added to the circuit resistance on 2 separate poles on the PCB board. ( the other hardware on the board is all brass, except for these screws)
the resistance increased slowly over time and as a result the increased resistance generated more heat than the Board, and fan could dissipate.
but this is only speculation....
I think you hit the nail squarely on the head with your theory of how things went bad.....It makes perfect sense, thanks for sharing.
 
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