Correct Voltage for Gents Pulsynetic Master Clock

Discussion in 'Electric Horology' started by Lincolnhill, Apr 28, 2007.

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  1. Aussie64

    Aussie64 Registered User
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    Dec 25, 2012
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    Hi John,
    I just found this thread whilst researching my latest find. I too have an early Gents Pulsynetic and was reading this thread for info on wiring, power consumption etc. Your serial number is also very close to my clock, mine is No 1410 and dated 18th May 1914 on a small paper label RH top of wooden case, case is also numbered 1410.

    Mick
     
  2. Aussie64

    Aussie64 Registered User
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    Dec 25, 2012
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    Hi,
    Does anyone know where to get replacement dials for these clocks (6 inch diameter to chapter rings, Roman Numerals) or should I just use generic paper dial over original?
     
  3. dw2007uk

    dw2007uk Registered User

    Dec 2, 2007
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    I recently acquired a C7 master clock, which is in near-perfect condition, complete with instructions and pendulum.

    The movement seems to be in good working order when I operate it manually, but it's not working properly when power is applied.

    I've tried various power sources (mains adapter, 12V sealed battery, and 'D' size batteries connected in series), but it seems there's not enough current flowing through the circuit. Indeed, when measuring the current using an ammeter, it seems only a couple of dozen milliamps are 'going through'.

    Does anyone know what the problem may be? Could it be that the coils are no longer any good?

    Also, I notice most C7s have a 'rheostat' resistor fixed below the movement. Mine hasn't got one (and there's no evidence that one was ever fitted), and it seems the one referenced earlier in this thread doesn't have one either. Is there any reason why one wouldn't be fitted?

    Thanks for any help. I can provide photos of the movement if required. :D
     
  4. eskmill

    eskmill Registered User
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    #54 eskmill, Apr 27, 2013
    Last edited: Apr 27, 2013
    Indeed, photos of your Gent C-7 Master Clock would help.

    You ask in part: "it seems there's not enough current flowing through the circuit. Indeed, when measuring the current using an ammeter, it seems only a couple of dozen milliamps are 'going through'."

    Without a diagram of your "circuit." I don't know exactly what circuit or part of the circuit is being observed.

    I would suggest that you measure the current at the most basic part or element of the time transmitter, the reset electromagnets. When the circuit closes, the current should be 220 milliamperes. The simplest scheme involves removing one of the connections to the reset electromagnets and inserting your ammeter in the circuit. Then, manually close the circuit to observe the measurement. Close the circuit with a wire jumper, or in some way short circuit the contacts.

    The Gent and like time-slave systems operate in a current loop. The master and all slaves are "daisy-chained" in series with the entire "loop" being supplied with an intermittent 220 Milliamper current each time the master circuit closes.

    If there are no slaves in the circuit, no current will flow. If only the pilot dial is present in the loop with the master time transmitter, then enough voltage is needed to provide between a minimum of 170 mA.

    Nearly every Gent C-7 has at one time been used with a system of secondary or slave dials and including its pilot dial. In a phone central office, 48 volts is readily available and is generally used for the clock system. A variable adjustable resistor or "rheostat" is generally supplied and mounted in the master case so as to adjust the current to through the loop. As a rule of thumb, each additional secondary or slave dial requires an additional 2 volts approximately. Thus a C-7 with no slave dials and only it's pilot dial in the series loop, should operate with three or four volts supplied to obtain the required 220 milliamperes.

    Analysis of the Gent or Synchronome system is best done by reducing the circuit to it's most elementary configuration; that is with only the master and a couple of dry cells in series; no slaves and no pilot dial.


     
  5. Edwardo

    Edwardo Registered User

    Jun 18, 2006
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    Also, I notice most C7s have a 'rheostat' resistor fixed below the movement. Mine hasn't got one (and there's no evidence that one was ever fitted), and it seems the one referenced earlier in this thread doesn't have one either. Is there any reason why one wouldn't be fitted?


    Chances are your clock is wired for 24vdc parallel not series connection

    This would have been done at the factory to suit the purchaser’s requirements


    What is the resistance of the circuit
     
  6. eskmill

    eskmill Registered User
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    Edwardo replied, "Chances are your clock is wired for 24vdc parallel not series connection."

    I don;t think so....although the order may have specified 24 volts, the Gent and Synchronome system both are "current loop" systems unlike American made Internatiional and Standard Electric Time company systems.

    Many of the English designed master-slave systems were/are "current mode" series loop systems. Voltage is not specified for the system operation although many were installed in Telco central offices where the talking voltage batteries were often either 24 or 48 volts DC. A variable resistance was often provided so that the current could be adjusted for proper operation.

    I've examined several Gent slaves, they all specify 220 milliampers and singly they draw the 220 mA at 2.0 volts.

    Again, DW2007uk, please be specific as to exactly where in the circuit your measurements were taken and if the pilot dial as well as the reset electromagnet is in the circuit.
     
  7. Edwardo

    Edwardo Registered User

    Jun 18, 2006
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    With all due respect Les

    Europe had many types of clock systems

    They even had some from your side of the pond (IBM, Simplex, International, Standard Electric etc)

    Sometimes a client would change their master clock and require it to operate their existing system



    A 24vdc parallel master was a common request.


    I used to service Gents installations in the UK during the 80’s and I came across many parallel and even reverse polarity C7 master clocks dating from as early as the 1930’s


    The earlier clocks seemed to be conversions but the later ones had no evidence of ever having a variable resistor


    Edd
     
  8. dw2007uk

    dw2007uk Registered User

    Dec 2, 2007
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    Thanks to those who have replied, and sorry for my delay in replying.

    I've looked up quite a few C-7s on the web and couldn't find any other examples of a resistor being missing (aside from the one referenced in this thread), so it's interesting what Edwardo says about the lack of variable resistor possibly meaning it's a 24v DC parallel 'model'.

    I'm not an expert on master clocks but I have a fairly good understanding of how they work, but apologies if any terms I use are a bit crude! When I initially tried the clock on the various power sources, I measured the amps flowing across the whole circuit (i.e. I positioned the ammeter in-line between the + of the power supply and the + of the clock's power entry). I attempted to measure the current at the reset electromagnets, but I couldn't find where to remove the connections for them.

    Based on the feedback I've received from you all, I've tried it on 24v DC. Whilst the electromagnets were more powerful, they still weren't powerful enough to function properly. Could it be that the required voltage may be even higher, say 36 or 48? I was using two (fully-charged) 12V 7Ah sealed batteries to generate 24V, and I'll be able to produce 36V when I've charged my third battery. I don't have a fourth one at the moment to try 48V though!

    I tried measuring the resistance in the circuit just now, but I think my multimeter's playing up so can't give accurate readings at the moment! :(

    Photos of the clock movement are available here: (large files which show lots of detail!)

    http://www.henryandjoey.co.uk/images/SAM_0515.JPG
    http://www.henryandjoey.co.uk/images/SAM_0516.JPG
    http://www.henryandjoey.co.uk/images/SAM_0517.JPG
    http://www.henryandjoey.co.uk/images/SAM_0518.JPG

    Thanks again for your help.

    David
     
  9. dw2007uk

    dw2007uk Registered User

    Dec 2, 2007
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    Just an update - I managed to get a new multimeter and also get better access to the electrics within the clock. The resistance measurement across each of the 'reset' coils is approx. 650 ohms. I'm guessing that's about right? I've checked all the other connections in the circuit and they seem to be fine, but the coils still seem to lack power when I try 24V. Hopefully I'll be able to try 36 and 48V soon, but I'm not sure I need to, and that the problem may lie elsewhere.

    Incidentally, looking at the clock movement (see the first photo I posted above), does anyone know what the components screwed to the inside of the case are for?

    Thanks
    David
     
  10. Edwardo

    Edwardo Registered User

    Jun 18, 2006
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    The components are resistors and capacitors
    Looks like your movement is set up for 1 min pulses judging by the extra contacts and connectors

    Can you load a pic of the slave movement to confirm this?

    One min pulses were often used to run time recorders (clocking in machines) which often ran on or around 60VDC (this does not mean your clock runs on this voltage)

    Attached is a drawing for illustrating how to set up a parallel Gents installation

    As you can see there is no variable resistor.
    Connections are + to + or 3 and – to 1
     

    Attached Files:

  11. dw2007uk

    dw2007uk Registered User

    Dec 2, 2007
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    Thanks for your reply.

    I ordered a 48V DC power supply off eBay and the clock runs a lot more happily from that, including the slave clock on the front (see photo of the movement of that here - http://www.henryandjoey.co.uk/images/SAM_0517.JPG ). It's definitely a 30-second impulse model though.

    Unfortunately, whilst the pendulum swings happily for a while and everything works as it should, it stops after a few minutes. There only seems to be about 50mA of current in the circuit when the contacts are closed, so I suspect the problem is a lack of current (even though the power supply claims to offer up to 300mA at 48V DC).

    Is it solely the weight from the gravity lever falling that provides the 'nudge' for the pendulum via the roller? I'm guessing there's something electrical involved too?
     
  12. eskmill

    eskmill Registered User
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    dw2007uk asks: "Is it solely the weight from the gravity lever falling that provides the 'nudge' for the pendulum via the roller? I'm guessing there's something electrical involved too?"

    There's absolutely no electro-magnetic force involved in maintaining the pendulum. The electro magnets only reset the gravity arm once every fifteen cycles or 30 seconds. Thus the pendulum is free from other than gravitational forces for twenty-nine seconds.

    If there's a large wire-wound adjustable resistor in the 48 volt circuit, you should adjust the resistance so that there is a 220 milliampere current in the clocks loop. Measure the current with the pendulum stopped by shorting the contacts that cause the reset.

    Much of the circuitry and wiring in the later Gent's time transmitter clocks is to adapt the basic circuit so as to enable the use of the telephone central office battery voltage. The basic Gent and Synchronome circuits operate from two or three cells; just enough voltage to provide 220 mA to reset the gravity arm and the pilot dial plus one or no secondary or slave clocks.
     
  13. Edwardo

    Edwardo Registered User

    Jun 18, 2006
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    Your clock is designed to run time recorders on one minute impulses

    The circuit is split into two parts

    The main clock and pilot dial runs on a 30 second impulse but the output to the external slaves / recorders is on a one minute impulse (as per the diagram that I attached)

    The red wheel on the pilot dial opens and closes the switch above it every other impulse

    This switch is connected in series with the extra switch on the reset arm to give one impulse every other reset, (one minute) through the “recorders” circuit

    You stated that your clock is drawing 50 ma @24volts dc

    If that is the case the resistance of the circuit should be around 480ohms

    To achieve 220ma @480 ohms you would need 106 volts (which sounds incorrect)

    Also you mentioned that the resistance of your circuit is 650 ohms (sound to much to me) so something is wrong


    I think at this stage you need to start eliminating wiring problems by taking the reset coils out of circuit and measuring their resistance

    If you need guidance to do this let me know

    The reset coils together should be less then 300 ohms

    Then check the pilot dial

    You would have a heaver duty pilot coil to drive the extra contact.
    This should be around 8 ohms

    Let me know what the results are and I can give you a definite power supply specification

    You will probably need to re work the wiring to convert this clock for “domestic” use

    This is quite easy and I can talk you through it

    E
     
  14. Mal 1200

    Mal 1200 New Member

    Sep 13, 2014
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    Hi guys,
    I am a newbie to this site and also a new owner of a Gents master clock, first of all I would like to identify it, I can't find a serial number. can anyone tell me where to look?
    Any help would be greatly appreciated
     
  15. Tinker Dwight

    Tinker Dwight Registered User

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    I don't have one but from the pictures, it would be on a piece of paper
    glued to the inside left of the top of the case.
    Tinker Dwight
     
  16. itspcb

    itspcb Registered User
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    In addition (to Tinker's input) there are (at least) two numbers stamped on the case. One on the vertical portion of the top rail and one on the horizontal portion of the bottom rail. True on my 1930's model. The stampings are small and light, about 3/32"
    There's nothing obvious on my movement when in its case.
    Peter
     
  17. Mal 1200

    Mal 1200 New Member

    Sep 13, 2014
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    Thanks for your help Tinker and Peter, there is no paper label and I'm not sure which rails you are referring to Peter, I am going to attempt to load some photos of it. Scratch that, photo files are too large to upload.
     
  18. Hans Vrolijk

    Hans Vrolijk Registered User
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  19. dw2007uk

    dw2007uk Registered User

    Dec 2, 2007
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    Hi Edwardo

    My master clock ended up getting put away for a few years but I've unearthed it again!

    Do your offers of helping me measure the resistance of the reset coils and rewiring the clock for domestic use still stand? If so, I'd gladly accept!

    Thanks
     
  20. rogerj

    rogerj Registered User

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    Hi Michael..Your original question was posted over 10 years ago and attracted plenty of advice and guidance. I'm sure if you summarised what you have done since and where you are now with the clock and re-posted the pictures which seem to have gone..someone would help. Also read the other current Gents clock post which may contain relevant info.
    Perhaps even start a new thread and ask the moderator to delete your last addition to this thread (and mine !)
     
  21. dw2007uk

    dw2007uk Registered User

    Dec 2, 2007
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    I'm pleased to say that after its stint in storage, I finally managed to get the clock working after a bit of oiling and replacing some of the old wiring!

    When I connect a multimeter in series with the positive side of the 48V DC supply, it records 52mA (15mA of this is the pilot dial). Does this sound right? I thought it'd be more than this and yet the clock seems to be functioning well (albeit just the transmitter and its pilot dial at the moment).
     
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