Hello all, quick question for the electronics experts. I'm trying to repair the control board on my migatronic mig welder, the stitch function has stopped working. Now I dont play with electronics much anymore but I think one of the caps has died.

The value on it has the micro farrad symbol before the value ie

u1
250v

does this mean its 1micro farrad or less than ie 1 pico farrad ?
I wonder because on the cicuit diagram the caps are shown as 0.1 but then the diagram has quite a few discrepencies and alterations


Thanks in advance

[Edited on 22/3/11 by fazerruss]

Hi there,

It's common to use the prefix (i.e. k for kilo, u for micro etc etc) as the decimal point in labelling resistors and capacitors. E.g. 2k7 would indicate a 2.7 kOhm resistor. I would suggest therefore that your u1 capacitor (0u1 but missing the 0) could be 0.1 microF. Havent seen labeling quite like that (but then I'm no electronics expert), but that would at least fit with your circuit diagram.

If you get the capacitance wrong by a factor of 10 then the stitch time will be out by a factor of 10 (too much capacitance = too slow).

1picoF is much smaller than you would normally expect to use, so try 0.1microF and see what you get.

I am no expert though.

I'm guessing 100nF

Yes, 'u1' will be 0.1uF (AKA 100nF). It's a relatively unusual way of marking caps, but I have seen it before a couple of times.

Is it an electrolytic capacaitor? These are the the most likely to die with age and heat.

quote:

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Originally posted by MikeRJ
Yes, 'u1' will be 0.1uF (AKA 100nF). It's a relatively unusual way of marking caps, but I have seen it before a couple of times.

Is it an electrolytic capacaitor? These are the the most likely to die with age and heat.

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Its a migatronic automig 180mx just in case anybody has an accurate circuit diagram for the pcb