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IBM IBM Master clock help

timelyrestorations

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Jan 26, 2001
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I have a 1940 IBM master clock that came out of one of the local schools. The mechanical portion of the clock works fine, as in when I manually wind the spring, it will continue to run until the reserve spring power is depleted. Unfortunately the coil will not energize to wind the spring as it is supposed to. I have had the clock at a so called "electronics" guru for the past 6 months. He assures me that the coil is good, but cannot figure out why it will not energize. I had heard of a conversion kit to by pass the coil, but he can see no way of doing this. Any suggestions of what I should check?
Doug

ibm1.JPG ibm2.JPG
 

sundy58

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Aug 23, 2014
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I have no knowledge of your clock, I do have general electronics knowledge. The coil can be checked with an ohm meter. If it is not an open then a DC voltage applied should cause the coil to energize. If there is a diode on the coil then only one polarity of DC voltage will flow through the diode/coil.
 

ibm clock

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Sep 5, 2005
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If you push in the relay by hand, does the winding armature pull in? On the front of the movent are two contacts. The upper one will close once a minute to wind the clock and advance slaves.
 

ibm clock

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Sep 5, 2005
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i attached a diagram of a typical master clock schematic. this was for an external power supply, but yours is internal, but does the same thing. When I find it, Ill post the circuit description.

from the front of the movement, the upper contact is the Minute Impulse contact. the lower one with the two contact blades is the Stop and Advance contacts

on the rear of the movment is the 2 second contact. this is the one activated by the arm when the pendulum swing. the next one down is a duration contact used if a programing device is present.

the minute impulse contact is closed once a minute to send 24v ac to the master relay. when the master relay closes, its sends DC current ( nominal 24v dc) from the rectifer (the gray object with the stacked plates) out to wind the clock and advance the slaves.


the stop contact is what selects the A or B wire. this is used in sending the correction pulses plus the advance pulses to the slaves.

the 2 second contact is uses to either advance the clocks when the Advance/Run switch is in the advance position.. it also send the correction pulses on the 59th minute.

The A B C connection go to the slave clocks. i need to refresh myself with operatin of the slave clocks on the ABC wires. for now focus on getting the master clock to wind

Hope this helps

IBM 601-9 master relay.jpg
 
Last edited:

timelyrestorations

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Jan 26, 2001
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Thank you! The modular clock winder is exactly what I'm looking for. The clock did come with 2 slaves, but I did not have any intention of having those hooked up.

Doug
 

ibm clock

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Sep 5, 2005
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The clock has been rewired. thats modern wire. only conclusion is it is miswired, if the tranformer is good. Are the fuses good? does it even work if you push the relay in by hand? does the relay operate if you close the minute impule contacts by hand?
 

ibm clock

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Sep 5, 2005
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What you really need is a wiring diagram. all i have are schematics. i have a wiring a diagram for a model 15 clock with program unit. it from an older clock so i dont know how accurate it would be. for now, ill see if these circuit descriptions will post.

ibm 1 jpeg.jpg ibm 2 jpeg.jpg ibm 3 jpeg.jpg
 

ibm clock

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Sep 5, 2005
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Next ill have to find the pages dealing with how to set it up to time all the cams with the clock hands to everyrhing is in sync.
 

ibm clock

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Sep 5, 2005
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I think I Figured out why it wont wind. Move the winding coil wires from terminal 4 and 5 and move then to terminal A and C just below terminals 4 and 5.
 

ibm clock

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Sep 5, 2005
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Ive found other threads you posted. i found one where you said the program unit advances. so,unless there is a miswire around where the clock coil is connected, im going to think the clock winding coil is open. have you ohmed out the coil yourself?
 

timelyrestorations

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Jan 26, 2001
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IBM Clock:

Thank you for the help thus far. I'm afraid to say that my knowledge of electrics/electronics is limited to turning a light switch on and hoping something happens! As far as the coil goes, the electronics shop I took it to swears that the coil is fine. I am presently putting a new cord and plug on the clock. when that is complete, I will run some of the tests you have suggested.

Doug
 

smfielding

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Nov 22, 2010
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Did you manage to solve this? I have a 25-7 running from a new power supply and relay box so I have some information on how to get it simply run, but couldn't help you with the correction part of the mechanism as mine doesn't have this fitted.
 
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