fazerruss
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| posted on 22/3/11 at 09:23 AM |
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capacitor value
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]
"if assholes could fly this place would be an airport"
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Liam
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| posted on 22/3/11 at 09:44 AM |
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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.
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matt_gsxr
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| posted on 22/3/11 at 11:01 AM |
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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.
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Daddylonglegs
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| posted on 22/3/11 at 01:12 PM |
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I'm guessing 100nF
It looks like the Midget is winning at the moment......
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MikeRJ
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| posted on 22/3/11 at 02:09 PM |
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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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fazerruss
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| posted on 22/3/11 at 04:24 PM |
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quote:
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.
No its a non polarised cap, sort of a metallised polyester. The PCB has a date on it August 1985  so its getting on a bit. I bought the machine
second hand 14 years ago and has served me well. The normal weld function works fine but I wanted to use the timed weld setting last week and noticed
the fault.
Ive got the circuit digram from a fellow student at college many moons ago and never needed it til now. Problem is the diagram isnt exactly right ahd
has extra components drawn on by hand.
"if assholes could fly this place would be an airport"
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fazerruss
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| posted on 22/3/11 at 04:27 PM |
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Its a migatronic automig 180mx just in case anybody has an accurate circuit diagram for the pcb
"if assholes could fly this place would be an airport"
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