Standard Clock DC Voltage rating?


New User
Mar 19, 2023
Good evening all, thank you for allowing me to join your site. I recently picked up six Standard clocks dated 1947, It appears they were removed right off the wall by snipping in incoming wires. I did an ohm check on them all and they all read around 10.7 ohms.. At this point I'm thinking I'm rocking and they're all gonna work, easy peasy. So I wired one of them to 120 VAC... mistake, took care of that motor.... So I took another clock and hooked up a small 12 VDC battery for an alarm system and I got a positive response... almost. One of the coils engergized, the pawl catch moved, but that was it, the motor did not activate. I'm thinking I need a higher VDC perhaps 24 volt? Attached is a photo of the front of one of the clock batches. Any help appreciated. thank you in advance. Don


NAWCC Member
Jan 27, 2022
You should study the movement carefully to understand how it operates before randomly applying different voltages and blowing them up.
Ohms law: I = V/R That should have informed you not to nuke it with 120V


Registered User
Dec 24, 2014
I suspect from your description of what happened with 12v that what you have are slave clocks designed to be used with a Standard Electric Master clock. The master clock will have sent out a pulse every minute, and the slave clocks advance 1 minute per pulse.

You will need to do some proper research on master slave clock mechanisms, then get hold of something to generate the one minute pulses if you want to use them to tell time. A proper master clock would be nice, but you can get electronic pulse drivers that work.

Tim Orr

NAWCC Star Fellow
NAWCC Member
Sep 27, 2008
Boulder CO
Good evening,, Hiyudon!

Frankly, I'm surprised that 120vac blew one of them up. I watched an antique dealer connect a Standard secondary clock to 120vac, and although it barked and buzzed and the minute hand moved jerkily around, when he was done, I bought the clock, and found it had sustained no significant damage. (At least I knew the coils weren't open!)

The secondary clocks I've worked on all ran on 24vdc. If you can't get one to advance on 12vdc, that would not surprise me. I've used three 9v batteries clipped together in series, at 27vdc, and they run fine.

First thing, as Mr. Wisty pointed out, you should probably determine whether these are masters or secondaries. If you remove the cans covering the movements, chances are you'll find simple secondary units. You can try activating them with your finger to see if they're mechanically sound. I'm betting they're all three secondaries, and probably at 24vdc.

Good luck!

Best regards!

Tim Orr


New User
Sep 29, 2021
There's a few variations of SET impulse clocks from that time frame.

1. AR or AR-3: two magnetic coils, both 24VDC. Coil on the right (when looking at the back) advances the hands once a minute when energized and released. Coil on the left releases the minute hand, causing it to swing to the 59th minute. Look for a weight on the gear.
2. AR-2: one magnetic coil, 24 and 48 VDC. 24 VDC does the minute impulse, 48 VDC does the hourly correction as described above
3. Series: one magnetic coil, no correction. Designed to be wired in series with other slave clocks, usually can be tripped with as low as 2 VDC

Generally the clocks will be marked with "AR" or "SERIES" on the back.

The AR clocks had their correction impulse during the 59th minute, usually between the 10th and 20th second. One variation did it during the 00th minute, but 59 was more common. Newer electronic master clocks handle correction incorrectly (Lathem, ATS), relying only on the correction impulse to advance from :58 to :59, which isn't how these are designed to work but it works fairly reliably. Some actuate both the minute and hour impulse at the same time (Lathem mini master), which overrides the correction impulse. Simplex 6350 and 6400 master clocks are especially awful at the correction as they skip the 59th minute all together and then do the correction sometime during the 59th minute.

I've built a few homemade electronic master clocks for schools trying to maintain their existing systems and I tend to put the correction impulse between the 25th and 35th second when writing the software. (I use a Raspberry Pi and a relay board). When the correction impulse occurs and the slave clocks are already at :59, nothing happens. The minute hand just clicks but doesn't move erroneously.

120 VAC to these clocks is unsafe to people and can damage the clock. There's a lot of bare wiring and metal, I don't know how anyone could surmise 120 VAC would be appropriate.
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