Author Topic: coil ratings question  (Read 178 times)

dudlydoo

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coil ratings question
« on: October 10, 2018, 09:51:56 AM »
Picked up a 12 inch dial wooden case Telechron.
Coil had a 12-D number printed on it.
I plugged it in before I noticed that, and it started to smoke.
I need to know if this is a different voltage coil than the usual. If I ruined it, I have extra coils and I would need to use a different coil anyway to run this clock if I either ruined it or need to switch to 120 volts.
   Anybody know here??
 Its a full size B rotor with the usual gear on the shaft end.
The rotor works on my test stand at 120 volts, and goes around once in sixty seconds, so ???

cable ulysses

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Re: coil ratings question
« Reply #1 on: October 10, 2018, 10:05:37 AM »
Somewhere on the forum there are data on the coil markings.  If memory serves, the number on the coil relates to the number of turns or possibly the dc resistance, diminished by a factor of ten.  Most or all of the "normal" 120 volt clocks have number from, say, 60 to 75.  correlates to a dc resistance of 700 ohms more or less.  You can measure this with an ohmmeter as a check.  That will be a coil for 120 volt power. 

I haven't seen a coil marked 12-D, but I'd guess it's set up for 24 volt operation.  Check with an ohmmeter.  Either it will be open if you fried it or I'd guess it would show dc resistance of 100 to 200 ohms:  too low for 120 volt operation.  If it's a lot less, the insulation is likely burned internally and there is an internal short.

In any event, it's time to replace it with a known good 120 volt coil.

Good luck.


henny

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Re: coil ratings question
« Reply #2 on: October 10, 2018, 02:49:48 PM »
A #12 coil is rated for 20 VAC.  (Probably was originally from a Nutone or Rittenhouse door bell clock).

I hope you didn't burn out the coil.  They are extremely scarce.  If it measures around 23 ohms it's probably a survivor.

henny

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Re: coil ratings question
« Reply #3 on: October 11, 2018, 09:42:42 AM »
Check your PM

 

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