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[tonyH]

Hello All,

This should possibly be under engineering but here goes.

I recently bought a Unimat 3 at a very good price. All the mechanical bits are fine and the only problem is the motor, or rather the translation of the part number for the starter capacitor. The motor runs perfectly on the lower of the twin speeds but shorts on the high speed. This seems to be a fairly common occurrence with my version of the EMCO motor. The general advice seems to be to do away with the capacitor but I'm wary of doing just that.

If I google F1740-327-5511 as the capacitor reference the only supplier is Swiss. Is there a way of translating the number to an equivalent UK type or is it best to go for the original source?

Any help would be appreciated.

Tony

[Jon]

Does your transparent wire go to earth?
I had one of these in a multi-master tool.
I ended up replacing the package with three discrete capacitors, in your case 0.027uF, 2x 2700pF
But (unless they are doing something strange) this is not a motor capacitor, just a suppression capacitor, so it may not be your problem.
unless the capacitors are jusr breaking down with the higher voltages of full speed.
If it is just suppression capacitor, you should be able to remove it (temporarily) to see if your problem persists.
Or permanently of you don't see any ill effects on radios/TVs around you.

So you need (assuming I read your part number right):
a 0.027uF 275V (or higher) X1 rated capacitor between blue and black,
and a 2700pF 250V (or higher) Y2 rated capacitor between Blue and transparent,
and a 2700pF 250V (or higher) Y2 rated capacitor between Black and transparent.

That should replace the unit.
I'll try to find links to suitable components when I get into the office if you need me to.
Rgds
Jon

[tonyH]

Thanks for that Jon,

The failure of the capacitor is, it seems, a common problem with the Emco motor on the Unimat 3, so I reckon the 250V bits can't cope with the agricultural mains supply we have round here!
I'll check the interference. I didn't notice any on the lower speed but it might be worth just putting new ones in place anyway while I've got the motor apart.
I freely admit that I know nowt about electronics, so if there's a simple 'solder x to y' guide and recommended bits I'd much appreciate it.

Thanks again,

Tony

[Jon]

OK, Thanks for the drawing, Ill draw something up for you shortly.
Rgds
Jon

[tonyH]

Thanks Jon, 

There's no urgency.

Tony

[malcolmfrary]

Did I see right on the drawing a reference to a "120 volt AC" supply?.  Unless the mains is reduced via a transformer, this could pop the capacitors.  Never having had a Unimat, just asking.

[tonyH]

Thanks Malcolm, I didn't spot that.

The drawing was from an American site, but the motor was built in Austria so the 250/275 volts for the capacitors are still valid.

Tony