Re: DC Power sources for a 1920's Synchronome master & Current Regulation?

Ian Richardson

I may be preaching to the converted, but clock systems such as the Synchronome are current controlled, and the recommended current through the system is 330mA.  The voltage applied will be dependent upon the number (and type) of slave dials in the series circuit. There is something to be said for using a voltage higher than the minimum required, and controlling the current with an appropriate series resistor.  In my house circuit, which includes a Synchronome (with 4 slaves) and a Gent (with 4 slaves and a programme unit) everything runs from a 50 v.d.c. supply.  I use physics lab type rheostats to control the current in each circuit to the relevant required values.

The current is not that critical and can be lower than the specified value, but ideally should not be too high otherwise the reset becomes a bit violent (and noisy!).  As Andrew pointed out, the adjustment of the air gaps in the master clock (and the slave dial mechanisms) should all be correct for reliable operation.  Should the current be too low, there is a "warning" given by the master clock in that the gravity arm will not reset promptly, but be helped by being nudged by the returning impulse pallet.  This is clearly audible both at the master clock and at any slaves in the circuit as, instead of a prompt "click" each half minute, there will be a prolonged click as the reset current starts and then ends about 1/2 second later.  Synchronome and Gent both produced a device called a "battery warning indicator" which sounded a bell or gong if the reset duration was too long.

Don't know if any of that helps, but I hope so.

Ian R
Somewhere in France

-----Original Message-----
From: Andrew Nahum <andrew.nahum@...>
Sent: Tue, 2 Mar 2021 18:00
Subject: Re: [synchronomeelectricclock] DC Power sources for a 1920's Synchronome master & Current Regulation?

I use 2 Duracells in series and the clock works well but it has to be in good adjustment on all the contact arm gaps etc. They last about a year. My impression is that more volts give more noise.

On Tue, Mar 2, 2021 at 3:54 PM John Hubert <jfphubert@...> wrote:
The master draws 300 - 350 mA …….. but the duty cycle is low; approximately 100 - 150 mS every 30 seconds, so the average is low.


On 2 Mar 2021, at 15:31, Thomas D. Erb <tde@...> wrote:

I'm not familiar with this type of master - but if it is really voltage-sensitive you can also use a diode - each diode will subtract .7 volts from the power supply.

alkaline batteries nominal voltage is 1.5VDC so 3 in series would give you 4.5VDC. 

If the master really draws 350ma - you would'nt get a lot of life - 
A D cell battery will give you 12000-18000 mAh
12000/350=34.2857 to 18000/350=51.4286

so between 34 and 50 hours of run time.  

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