# syncronome tower clock

#### Lewis Luffman

##### Registered User
CML Snyder public school tower clock , 1910 , 1920?
minute hand is 24 inches long
dial marked Synchronome London
I took it apart 35 years ago to replace the spindles that had rusted out . life got in the way and I never put it back together, hmmm ,
now I cant remember, because its so different from an ordinary clock
i am curious if a regulated 9 volt source would power it

#### Ralph

NAWCC Member
I think you have a slave clock. There would have ben a master clock to power and regulate it.

This might do better in theElectric Clock category.

Ralph

#### shutterbug

##### Moderator
Staff member
NAWCC Member
I think the same thing. I'll move this over to electric clocks for more input.

Jmeechie

#### Toughtool

##### Newbie
This is an impulse secondary (slave unit) and requires a pulsing unit to advance the time. The pulsing unit can be the master clock or you can purchase one just for this movement. Something like this: Model 1900W-UNV Modular Clock Winder - Ken's Clock Clinic (no affiliation) Call them first before ordering.

Please do not start putting voltage on the terminals without thinking about the correct voltage. I think this is a low voltage movement, so I would first try a C cell 1.5 volt battery to see of the armature attracts. Move up from there. A variable power supply would be helpful at determining the correct voltage. Then measuring the coil's resistance you can compute the current from the Ohm's law formula I=E/R .

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#### Ralph

NAWCC Member
A variable power supply would be helpful at determining the correct voltage.
Synchronome's actually measure and control the current to their slave(s)... a current loop, in the case of multiples. I don't have the target current value handy right now...

" Synchronome systems, whether masters or with slave circuits are designed to run at constant current of 300-330mA, not at particular voltages. The constant current for a seconds slave circuit is 75mA for both the early and later type of seconds switch.Feb 21, 2019 "

Ralph

#### Lewis Luffman

##### Registered User
This is an impulse secondary (slave unit) and requires a pulsing unit to advance the time. The pulsing unit can be the master clock or you can purchase one just for this movement. Something like this: Model 1900W-UNV Modular Clock Winder - Ken's Clock Clinic (no affiliation) Call them first before ordering.

Please do not start putting voltage on the terminals without thinking about the correct voltage. I think this is a low voltage movement, so I would first try a C cell 1.5 volt battery to see of the armature attracts. Move up from there. A variable power supply would be helpful at determining the correct voltage. Then measuring the coil's resistance you can compute the current from the Ohm's law formula I=E/R .

as you suggest, I will proceed cautiously

#### Lewis Luffman

##### Registered User
Synchronome's actually measure and control the current to their slave(s)... a current loop, in the case of multiples. I don't have the target current value handy right now...

" Synchronome systems, whether masters or with slave circuits are designed to run at constant current of 300-330mA, not at particular voltages. The constant current for a seconds slave circuit is 75mA for both the early and later type of seconds switch.Feb 21, 2019 "

Ralph
I appreciate it
I think you have a slave clock. There would have ben a master clock to power and regulate it.

This might do better in theElectric Clock category.

Ralph
I should have mentioned in my description , that the master clock is on display t the wellington museum.
perhaps i can get picture of it to add to my post
its a beautiful grandfather size and in pristine condition
thanks

#### Toughtool

##### Newbie
Synchronome's actually measure and control the current to their slave(s)... a current loop, in the case of multiples. I don't have the target current value handy right now...

" Synchronome systems, whether masters or with slave circuits are designed to run at constant current of 300-330mA, not at particular voltages. The constant current for a seconds slave circuit is 75mA for both the early and later type of seconds switch.Feb 21, 2019 "

Ralph
I can not disagree with your 300mA current, especially if Google says it is true. I was thinking the current of a unit is more like 200 mA. I don't have one to look at, or measure. However I doubt that the old Synchronome masters actually measured and controlled the current itself. The current was most likely adjusted by a technician by varying the supply voltage so that the current was at the needed 300 mA, as they added or subtracted units from the system.

This is a series circuit and the same current will flow through each unit. You should review Kirchhoff's voltage law. Basically the sum of the individual voltage drops will equal the source voltage. A secondary has a coil with a DC resistance and can be measured. From the resistance and known current we can compute the voltage drop across each unit from Ohm's Law, E (voltage) = I (current )* R (resistance in ohms). You can measure the voltage across each coil with a voltmeter and add them up. You will find this sum will equal the source voltage.

I believe the quoted Google reference "not at a particular voltages." refers to the supply voltage, not to the individual coils in the circuit. They will have a voltage drop based on the coil resistance at the 300 mA current. E=I*R

In an IBM master clock system the secondaries are in parallel. That means the supply voltage will be either be 12V, 24V, 48V,120V direct current. 24 volts is the most common. Here the power supply only needs to have the current capacity for the added additional currents when units are added (or subtracted). No voltage adjustments necessary at the master.

#### Lewis Luffman

##### Registered User
thanks
I may have overestimated my capabilities. but I have time to figure it out

#### Toughtool

##### Newbie
Lewis,
Don't be discouraged about the electronics. That's actually the easy part. After you fix and reassemble the movement, I think you will find that a single 1.5 volt alkaline battery will operate it. Positive to one terminal, negative to the other terminal, for your first electrical test.

You have a very nice looking secondary and while it is going to take a lot of work to restore it to it former beauty, it will be worth the effort.

Joe

#### Ralph

NAWCC Member
Google is only repeating what others have documented. Robert Miles , who has wrote the book on Synchronomes says they put an ammeter in series with the loop and use a sliding resistor to adjust the current. He goes on to say that the master clock , which typically has a slave dial will usually run on about 4.5 volts and each added slave in series might need about .8vdc additional at the source supply.

Based on the image you posted, it looks like a #3 larger dial movement, suitable for a 2 to 3 ft dial. If my estimate is correct, the main wheel is about 3” in diameter on a 4” x 4” base. The Miles book mentions the #4, the next largest movement movement has a resistance of 23 ohms and requires about 7.5 vdc for operation. The 330ma requirement was used on all size movements.

Ralph

#### Toughtool

##### Newbie
Ralph,
Great information that Lewis will no doubt need. Thanks for posting it. We now know the voltage required to provide the 330 mA of current for a #4 movement. A larger diameter clock will need more power because of the longer and heavier hands. To zero in on this movement only a resistance measurement is needed to find the voltage needed to provide the 330 mA. Second option is to monitor the current and adjust the voltage (sliding resistor) until you get to 330 mA. Just like the technician would do on a maintenance call.

My 1.5 volt reference was based on a different post where a 1.5 volt battery did operate the movement at 200 mA. So obviously not relevant here.

#### John UK

##### Registered User
The date given in the first post seems to tie in with the clock movement. The wooden former resistor (wired in parallel with the coils for spark suppression) was used up to around the mid 1920s. but the font and case used for the patented stamp was changed, probably around 1915, from the upper case letters with a font with quite pronounced serifs to a lower case 'sans serif' type font. At about the same time, an "English Made' was added - but this may be hidden under the connector block. The spring clips were adopted around 1910 (ish).

My best guess is that your clock movements would date to between 1910 and 1915 - but I would qualify this in that the comments are based on the 'standard' sized movements. I would expect the larger movements (like these) to have changed at similar dates, but again a guess.

It will be very satisfying to get such an early movement running again. As has been said above, 330 mA would be the correct current for a Synchronome - and I suspect will need around 7.5 Volts.

#### Lewis Luffman

##### Registered User
your date estimate coincides with the construction date of the school . have not found the exact date yet. there is very little info on line
i believe the masterclock is on display at the Quaker museum . its quite large and in perfect condition .
maybe the will help me with a picture of the labels. i seem to recall a 9 volt battery

#### John UK

##### Registered User
If you could get a picture of the master clock - that would be great - if it is the original, the serial number on the bottom of the NRA plate (see attached) can give a good idea of the date for you. As a guide, serial number 100 was issued circa 1910 and by 1915 up to about 500. Early master clocks were sometimes replaced in service as at the time they were very much 'working equipment' and reliability was key for a public building clock.
A list of known Synchronome serial numbers (against dates where known) is kept by the Antiquarian Horological Society in the UK and this enables reasonably certain dating. Sadly, no original register of serial numbers and customers has survived as far as is known.

#### Toughtool

##### Newbie
Here is a simple variable voltage test setup. Most people have a few 12 Volts DC wallworts or old computer power adapters laying around. Anything from 12 volts to 24 volts DC should work fine.

If not, buying everything new is not too expensive. The DC to DC converter connects to the 12-35 volt voltage adapter and outputs a variable voltage based on the voltage adjusting screw on the "Blue" component on the circuit board shown in the photo. This converter even has a built-in voltmeter for measuring the input voltage and the adjusted output voltage. Just connect the 10 amp ammeter in series with the secondary's coil and adjust until you see 330 mA. (Do not use the 200mA scale here) (Do not measure voltage with the meter in the ammeter configuration, it will kill the ammeter section) Set meter to the 10 amp range.

Digital multi-meter, \$9.99
DC to DC converter, \$9.99/2
2 amp 12V power adapter, \$7.98

As of Feb,13, 2022.

Digital multi-meter: Amazon.com

Adjustable DC to DC converter: Amazon.com: HiLetgo 2pcs LM2596 Adjustable DC-DC Step Down Buck Power Convert Module 4.0-40V Input to 1.25-37V Output with LED Voltmeter Display : Electronics

#### Lewis Luffman

##### Registered User
I tested the clock using a universal ac/dc adaptor with a variable range of 3 to 12 volts. using 3 volt setting .
the adapter is 500ma, so I cant use it extensively, until I do more research to make sure it wont harm the coils
it worked perfectly , each time I touched the contact, the minute hand advanced by 1 tooth on the center gear. The minute hand advanced by 1 minute? or part of?
as dr. Frankenstein would say ****ITS ALIVE*****
But this leads to more questions . the adapter has a polarity switch, which way is correct?
and, since the unit with the hands works independent of the other one that's in pieces , what function does that one serve?
most importantly , when I get it working , how do i convince my wife , that it rightfully deserves a prominent spot on the living room wall.
I hope to get pics of the master clock and its label from the wellington museum , long ago I was president of their board, so I hope they will help me.
wish me luck
and thanks for your interest in my project

#### John UK

##### Registered User
120 teeth on the wheel so half minute per pulse. Half minute impulses were standard (at that period) for most of the British master/slave clock systems (Synchronome, Lowne, Silent Electric) and the later Gillett & Johnston and English Clock Systems (ECS/Smiths). 1 minute impulse systems were used in Europe and later Synchronome, Gents and ECS all did 1 minute systems - though they remained less common in the UK.

As factory delivered, polarity is unimportant (there is a coil and a resistor, neither of which are polarity sensitive). Occasionally, diodes have been fitted for better spark suppression, which does make them polarity sensitive, but you would see that - and it is unlikely in an old clock that has not been in use in recent times.
Two units? Were there at some stage two dials? Maybe another dial somewhere in or on the building? Maybe one was a spare, though I'm not aware that spares were usually held, but perhaps being an unusual clock (big movements are quite rare) and a long sea journey (in those days) from the factory in London, a spare may have been held?

Since a single master clock can drive numerous dials, do you know if the building had originally internal dials located around the various parts of the building?

#### Toughtool

##### Newbie
You are saying that the adapter has a rating of 500 mA, not that the movement is drawing 500 mA. You need an ammeter to see if the 3 volt across the coil produces the required 330 mA of current that Ralph mentioned in post #11. A \$10.00 multi-meter is a good investment, and will produce good information wired as shown in the my schematic in post #16. Mainly that the voltage is or is not the 7.5 volts across this coil that produces the 330 mA of current. You can also measure the coils resistance with the same meter, to verify the 23 ohms of resistance mentioned. Remember, if the resistance does not change then a lower voltage will result in a lower current. Ohms Law, I=E/R, If E goes down then I goes down. If E goes up then I goes up. (also E=I*R, same thing) You could of course compute the resistance from the third iteration of Ohms law, R=E/I, once you know the voltage and current. .

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#### Lewis Luffman

##### Registered User
You are saying that the adapter has a rating of 500 mA, not that the movement is drawing 500 mA. You need an ammeter to see if the 3 volt across the coil produces the required 330 mA of current that Ralph mentioned in post #11. A \$10.00 multi-meter is a good investment, and will produce good information wired as shown in the my schematic in post #16. Mainly that the voltage is or is not the 7.5 volts across this coil that produces the 330 mA of current. You can also measure the coils resistance with the same meter, to verify the 23 ohms of resistance mentioned. Remember, if the resistance does not change then a lower voltage will result in a lower current. Ohms Law, I=E/R, If E goes down then I goes down. If E goes up then I goes up. (also E=I*R, same thing) You could of course compute the resistance from the third iteration of Ohms law, R=E/I, once you know the voltage and current. .
thanks
i will buy a multimeter and try your advice .the second mechanism is almost reassembled . I cleaned it and I must say, its a beauty to behold. the quality of the brass is amazing.

#### Lewis Luffman

##### Registered User
120 teeth on the wheel so half minute per pulse. Half minute impulses were standard (at that period) for most of the British master/slave clock systems (Synchronome, Lowne, Silent Electric) and the later Gillett & Johnston and English Clock Systems (ECS/Smiths). 1 minute impulse systems were used in Europe and later Synchronome, Gents and ECS all did 1 minute systems - though they remained less common in the UK.

As factory delivered, polarity is unimportant (there is a coil and a resistor, neither of which are polarity sensitive). Occasionally, diodes have been fitted for better spark suppression, which does make them polarity sensitive, but you would see that - and it is unlikely in an old clock that has not been in use in recent times.
Two units? Were there at some stage two dials? Maybe another dial somewhere in or on the building? Maybe one was a spare, though I'm not aware that spares were usually held, but perhaps being an unusual clock (big movements are quite rare) and a long sea journey (in those days) from the factory in London, a spare may have been held?

Since a single master clock can drive numerous dials, do you know if the building had originally internal dials located around the various parts of the building?
thanks .the info about the tooth count / time relationship, it will be extremely valuable . I will refer back to your comments as I go along.
the Wellington museum is closed for the season, so their input is on hold . Wellington is village of 1500 people .the public school is the only public clock there , so the system cant be too sophisticated. long ago I knew all the old timers who could have told me all about it , but now i live a hundred miles away
its surprising how little people know about an artifact so prominent in their community. (the school's existing clock)
regards Lewis

#### Toughtool

##### Newbie
Since you have two movements, I have updated the schematic for running both units from a 24 volt power source. The unit that Ken's clock clinic should work for your movements but you should call them to make sure. Here is a quote from their description of the pulsar they sell. It says the unit can output 30 second pulses, two per minute as mentioned in John's post #18.

"Remember, the Model 1900W-UNV Modular Winder is the BEST choice for driving master and secondary clocks by Standard Electric, ITR, IBM, or Stromberg! Timekeeping accuracy is typically better than 3 seconds per month. Can also be configured to drive 30 second impulse Self Winding Clock Co. secondary clocks." ( Model 1900W-UNV Modular Clock Winder - Ken's Clock Clinic )
a 50 ohm, 5 watt variable resistor can be sourced from Digikey, at:

#### Lewis Luffman

##### Registered User
I have cleaned and reassembled the the lower movement , fortunately, i had not lost any of the parts after many years and several moves .i can now see how it operates , but there are several small springs that i don't yet have in place, but the levers advance the gears as intended. i have quite a few power sources, still have to figure that out . the clock winder you suggest seems appropriate, although their description doesn't mention Syncronome
the movement seems to be the strike counter mechanism with a rack and snail drive .

#### bruce linde

NAWCC Member
Donor
Half minute impulses were standard (at that period) for most of the British master/slave clock systems (Synchronome, Lowne, Silent Electric) and the later Gillett & Johnston and English Clock Systems (ECS/Smiths). 1 minute impulse systems were used in Europe and later Synchronome, Gents and ECS all did 1 minute systems
my gents c7 master is every 30 seconds

#### Toughtool

##### Newbie
i have quite a few power sources, still have to figure that out .
The winder unit is supposed to provide the 24 volts needed to power the units. Quote from description:" This efficient module provides the proper voltage and pulse signal to wind or impulse any master and secondary (slave) clock of USA manufacture such as Stromberg, International Time Recorder, IBM, Standard Electric, and others requiring between 1.5 volts and 25 volts. Powered by four alkaline D cells ".

Personally, I would use an adapter, not batteries, but that's me. It is possible they are using a DC to DC boost converter internally to get from 6 volts (4 D cells) to 24 volts. I don't have one of these winders and I've never seen one so if someone here that does use one can offer some insight.

The unit may have an adjustable voltage which would eliminate my resistor and 24 volt requirement, (my schematic, post # 22) and output only the 7.5 or 15 volts (for two units) at the 330mA current needed. Current adjustment would be the same. Adjust the voltage to get 330mA, remove the ammeter and watch time fly.

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#### John UK

##### Registered User
my gents c7 master is every 30 seconds
You are quite right! It was my mistake to omit Gents (probably the most popular and well known of them all in the UK) from the group of "Synchronome, Lowne, Silent Electric, Gents". The Thornbridge, C6, C7 were all 30 second. Some of the later Gents (Chronopher) were 1 minute.

Gents did some beautifully engineered turret clock movements called 'waiting train' which were synchronised by a master such as a C6, C7. There were several models of different sizes - the largest could manage enormous dials.

#### Lewis Luffman

##### Registered User
its quite a large clock. the minute hand is 24 inches from the center . finding a dial at a reasonable price could prove challenging.
have a problem with the secondary movement advancing . it may be an incorrect reassembly, since i have no schematics, or the weathering of the mechanism, which seems to have survived harsh conditions . i just cant get the pusher to advance the main gear correctly
don't worry, i never give up

#### RODALCO

##### Registered User
Looking at the coil wiring that is more a 220 to 300 mA series circuit movement coil.
Interesting that there are two coils next to each other.
Maybe because of the heavier long dials, although often a counterweight was fitted as well.
The normal clock movements have one coil.
Most Gents and Synchronome clocks were 30 seconds movements.

#### John UK

##### Registered User
The larger Synchronome slave movements used two coils - running at a nominal 330 mA impulsed every 30 seconds (hence 120 teeth on the minute hand wheel). The two coil movements are most often seen on the Synchronome 'programme controllers' used to ring bells in schools, factories etc. but were also supplied for large conventional dials such as used on turret and building external dials.

The larger movements were also 'double locked' meaning that the arm from the solenoid which carries the driving pawl is locked forward (by an additional peg on the backstop arm) in the absence of the electrical impulse. This was also used on the normal sized movement on some early movements (between about 1909 and 1914), but dropped from the normal size versions. It is said to have been retained on the larger movements in order to provide better protection from the hands being accidentally moved from wind action on the hands of external dials.

The attached photo shows a 'normal' sized movement with double locking provided by the circular slotted peg directly below the 'heel' of the driving pawl which operates in a semi circular notch in the arm carrying the driving pawl. This movement dates to around 1910-14.

#### Lewis Luffman

##### Registered User
hi John
your information is extremely helpful . I am having a lot of trouble with that double locking mechanism on the strike movement , it always seems to want to be in the wrong position, preventing the pallet from advancing the gear ,, knowing the correct terms for the parts, will help me find solution. weather is bad here right now so I spend lot of time experimenting to find the solution.

fortunately the slave clock with the hands is much less complex , and it works perfectly. it will be on the wall of the rec room in few weeks, or a little longer, depending ,how obstinate my wife is
I am trying to find the correct winder and figure out how to get a proper dial without going broke
thanks

#### Lewis Luffman

##### Registered User
I found the circular plastic disk on the side walk ,while walking my grandkids ,on Dundas street in Toronto , it's scrap material from a renovation nearby . while its only 3 feet instead of the required 4 , its suitable for a trial run . I took your advice, and purchased a clock winder from "Kens Clocks" .
it works perfectly , easily adjusts to 30 second interval, and keeps accurate time . I am using Ken's 4 d battery holder to power it , until I can buy a proper power supply.
as you can see in the video, the hand lurches backward at each movement. I expect , over time, this would cause excessive wear. I just have to figure out what to adjust to correct it. I really appreciate the advice i received on the forum . I would never have figured it out.
regards to all

#### Attachments

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#### demoman3955

##### Registered User
hi John
your information is extremely helpful . I am having a lot of trouble with that double locking mechanism on the strike movement , it always seems to want to be in the wrong position, preventing the pallet from advancing the gear ,, knowing the correct terms for the parts, will help me find solution. weather is bad here right now so I spend lot of time experimenting to find the solution.

fortunately the slave clock with the hands is much less complex , and it works perfectly. it will be on the wall of the rec room in few weeks, or a little longer, depending ,how obstinate my wife is
I am trying to find the correct winder and figure out how to get a proper dial without going broke
thanks
I have a master and 5 slaves, none of which ive ever had running due to not having a power supply. If you need any photos, i can shoot a couple to send to you. Actually now that i think about it, ill have to try to remember where i stored the slaves. Ive had the clock for close to 30 years and never had it running, and clock repair shops where im at cant seem to figure out much about them.

#### Lewis Luffman

##### Registered User
I have a master and 5 slaves, none of which I've ever had running due to not having a power supply. If you need any photos, i can shoot a couple to send to you. Actually now that i think about it, ill have to try to remember where i stored the slaves. Ive had the clock for close to 30 years and never had it running, and clock repair shops where im at cant seem to figure out much about them.
I would love to see the pictures .( lewis.luffman@gmail.com) I would guess, that having such a complete set is rare .
they are actually very simple in the way they work, when the solenoid coil is electrified it pulls the arm back , when the current stops a spring pushes the arm forward , moving the gear forward by 1 tooth, either , every 30 seconds like mine , but usually 60 seconds.
the master clock regulates the power interval.
the power supply is not difficult once you know what you need .everybody has a box of power ac adapters from various discarded electronics , maybe you already have it.
the people on this forum were so generous with their advice .. take a look at their suggestions regarding my clock. You must be tempted to post it .

#### demoman3955

##### Registered User
I would love to see the pictures .( lewis.luffman@gmail.com) I would guess, that having such a complete set is rare .
they are actually very simple in the way they work, when the solenoid coil is electrified it pulls the arm back , when the current stops a spring pushes the arm forward , moving the gear forward by 1 tooth, either , every 30 seconds like mine , but usually 60 seconds.
the master clock regulates the power interval.
the power supply is not difficult once you know what you need .everybody has a box of power ac adapters from various discarded electronics , maybe you already have it.
the people on this forum were so generous with their advice .. take a look at their suggestions regarding my clock. You must be tempted to post it .
what really sucks is ive moved and have the slaves in a box somewhere, and the pendulum is somewhere else and stacks of stuff in between. I even used to have the original book and paperwork, but im thinking it is either packed away or the clock repair guy lifted it. I have one brass case, one copper and 3 wood cased slaves. The funny thing is my dad bought it when he was on a trip to oregon, and i now live in the same town the clock came from.

#### Lewis Luffman

##### Registered User
how big are these clocks? how old are they? makers name? since they come from the town you live in , you have just got to find them. interest. .
mine came from the bell tower of the public school my kids' attended. the dial is 4 feet across , made in 1910-14
we have moved many times , and I have stuff packed away, that I haven't seen in decades . months ago, I found the seal of his majesty's ships. it was used to put a wax seal on the bill of laden etc. when the ship was away from home port. since they could virtually create currency , they are never private collections

I solved my power supply problem. a charger that belonged to an old Motorola flip phone , perfect voltage and amps..

#### demoman3955

##### Registered User
how big are these clocks? how old are they? makers name? since they come from the town you live in , you have just got to find them. interest. .
mine came from the bell tower of the public school my kids' attended. the dial is 4 feet across , made in 1910-14
we have moved many times , and I have stuff packed away, that I haven't seen in decades . months ago, I found the seal of his majesty's ships. it was used to put a wax seal on the bill of laden etc. when the ship was away from home port. since they could virtually create currency , they are never private collections

I solved my power supply problem. a charger that belonged to an old Motorola flip phone , perfect voltage and amps..
I posted pics and measurements on the elestric clock section

#### John UK

##### Registered User
I have a master and 5 slaves, none of which ive ever had running due to not having a power supply. If you need any photos, i can shoot a couple to send to you. Actually now that i think about it, ill have to try to remember where i stored the slaves. Ive had the clock for close to 30 years and never had it running, and clock repair shops where im at cant seem to figure out much about them.
A master and 5 slaves needs about 4.5 Volts (DC) for the master including it's inbuilt dial, and 1.5 Volts per external slave, so a 12 Volt supply should be absolutely fine. Current is 330 mA and the duty cycle is very low (roughly 100 milliseconds impulse every 30 seconds). This can be supplied from a 'wall wart' plug in available very cheaply.
I would love to see pictures and also know the serial number of the master, which is stamped on the bottom of the "NRA" plate on the main movement, and probably 3 or 4 numerals, possibly preceded by a letter. See example below. Knowing the serial number, I could probably give you an approximate date for the clock. There is a lot of information on the ClockDoc website with setting up instructions etc. available. Go to the Synchronome section of the website. Good luck.
EDIT - I have found your pictures in another post! I would still love to see the serial number of the master - which looks to date to pre 1953 based on the coils being insulated with green covered wire. It is a nice set.

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#### demoman3955

##### Registered User
A master and 5 slaves needs about 4.5 Volts (DC) for the master including it's inbuilt dial, and 1.5 Volts per external slave, so a 12 Volt supply should be absolutely fine. Current is 330 mA and the duty cycle is very low (roughly 100 milliseconds impulse every 30 seconds). This can be supplied from a 'wall wart' plug in available very cheaply.
I would love to see pictures and also know the serial number of the master, which is stamped on the bottom of the "NRA" plate on the main movement, and probably 3 or 4 numerals, possibly preceded by a letter. See example below. Knowing the serial number, I could probably give you an approximate date for the clock. There is a lot of information on the ClockDoc website with setting up instructions etc. available. Go to the Synchronome section of the website. Good luck.
EDIT - I have found your pictures in another post! I would still love to see the serial number of the master - which looks to date to pre 1953 based on the coils being insulated with green covered wire. It is a nice set.
View attachment 705135
here ya go. its the first time i was able to see it thanks to my camera. lol

#### John UK

##### Registered User
C421 dates to either late 1931 or early 1932, so about 90 years old. It is one of the "Coventry" series, made for Synchronome under contract in Coventry (UK) - designated by the C prefix. A distinguishing feature is a smooth inside radius to the bend of the gravity arm. Normal (i.e. non-Coventry) clocks have a small 'step' either side of the radius. Approx 850 C series were made between 1928 and some time in the early 1940s (though the end date is rather uncertain as it was wartime). Coventry clocks are often fitted with the smaller (No 1 size) pilot dial slave movement. Around 100+ are known to be still in existence.

#### demoman3955

##### Registered User
C421 dates to either late 1931 or early 1932, so about 90 years old. It is one of the "Coventry" series, made for Synchronome under contract in Coventry (UK) - designated by the C prefix. A distinguishing feature is a smooth inside radius to the bend of the gravity arm. Normal (i.e. non-Coventry) clocks have a small 'step' either side of the radius. Approx 850 C series were made between 1928 and some time in the early 1940s (though the end date is rather uncertain as it was wartime). Coventry clocks are often fitted with the smaller (No 1 size) pilot dial slave movement. Around 100+ are known to be still in existence.
I started to think about the fact that no one mentioned anything about wire lengths to slaves and how it may effect the power and amperage needed. In my case, it wont matter because i plan on having the slaves next to the master.

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