Decastar 180

[tjolle62]

Hi guys,
for many years ago i bought a Deca 180 Mig/Mag which i had a great use of
in many different car projects.
lately i experienced problem with wire feed curcuit and the pot felt sloppy and
last weekend my wire feed went south !
after checking the pot i found out that the carbon trace was totally broken
and i have electronics as a hobby for many many years i have about 50 pcs
of potentiometers in my bins from 50 ohm - 1 Mohm Lin / Log types so a
replacement should be a jiffy BUT !
on this pot is NO markings whatsoever and measure the old one is out of
question so i contacted my local rep and Deca itself with no success,
my local rep sad i have to replace the whole controll card for £50.
For me thats is no go to spend £50 for a £0.50 part so now i wonder if anyone
here knows what resistance i need to replace my broken pot ?
I tried I-net without any luck for info or even a schematic for this unit.

 

[mike 109444]

You should be able to measure the good bits of the carbon track to get a rough value of the pot. This will allow you to select one of you spare pots close to the value. The using three fly/jumper leads, connect to the board and try feeding some wire from your mig to see if it feeds at about the same speed as before. If not go up or down a value. By using the jumper leads it saves soldering in and out pots and risking lifting the pcb tracks.

 

[tjolle62]

Decastar 180 Fixed.

Well it wasn't easy but after some tricks and bending i founded out that pot should be around 1K and the only 1K pot i got was a simular that was from
factory ( cheap and open style )little better quality but still open,
which for me is insane to have a open pot in all that smoke and stuff that
surround us i a garage especially while welding so i tried my endless source
of supplies named e-bay.
Jackpot ! found a sealed 1Kohm linear pot in UK for around £4 incl shipping
it was old but brand new *NOS* and of super quality and today i got'it and
mounted it on my little machine and only thing that had to be modifed was
a adapter for the shaft that is only 4mm and all my knobs and original is 6mm
so i took a 6mm brass screw in the lathe and drilled a 4mm hole and cut off
at 12mm length and then my dremel with a cutoff disc and sliced'it and there
a 4/6mm adapter so after solder'it to control board i also replaced 3 e-caps
to super quality ones and back on with covering and time for testing.
Damn !! it was smooth,,,, and what a difference it was.....
is like a totally new welding machine.
the wire feed is so exactly in linearity so it's almost hard to belive so
job well done i'll say so if anyone else have problem with wire feed pot on a
Decastar 180 so replace'it with a good quality 1 Kohm lin pot and it's done.

 

[mike 109444]

Makes you wounder how many wire feed problems may be due to the pot breaking down (before going completly) If the pot was a volume control on audio equipment you would notice the crackel when adjusting but on a mig it should crackel!