Re: Total Resistance In The Synchronome?

Ian Richardson


I've no doubt that others will chip in on this one.  I wouldn't take too literally what Arthur wrote as there would be quite a variation in values due to manufacturing tolerances.  The nominal resistance values help establishing roughly what voltage will be required, but in the final analysis, it's the current flowing through the whole system (which includes the system wiring) which matters.  With remote slave dials, the inter-clock wiring could easily amount to several Ohms, making a mockery of your calculations!

Also note that there is hidden wire-wound resistor behind the movement plate which is shunted across the coils to act as a rudimentary spark quench.  Have you taken that into account?

Ian R
Macclesfield, UK

-----Original Message-----
From: Brian Cracknell <brcracknell@...>
Sent: Mon, 29 Jun 2020 12:31
Subject: [synchronomeelectricclock] Total Resistance In The Synchronome?

According to Mitchell's "Setting to Work" instructions the total resistance in the Synchronome is made up of of 8.7 ohms (main solenoid) and 2.45 ohms (pilot slave) giving around 11.15 ohms total. My Synchronome however (an early 1920s, apparently unfiddled-with one with the original green cotton still on the coils) seems to have a resistance of 7.00 ohms showing on the ohmmeter when the circuit is closed. This reading is also supported by the fact that my power supply shows 3.3 volts on the voltmeter and when I add a 3 ohm resistor (providing 10 ohms total resistance) I get the required 0.33 amp current showing on my ammeter.

So my question is, does anyone have a not-in-use Synchronome that can be checked to see what the resistance is on that?

And my other, key question: if it turns out that others do have the 11 ohms as Mitchell mentions, what can have happened to mine to make it be different? Looking at the wiring, one wire goes into the bottom coil and another wire comes out the top coil so they do both seem to be wired up.


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