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IBM IBM 25-7 Help needed

matthiasi

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Dec 3, 2010
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Kelowna
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OK, so I'm working on my first IBM Master / Slave setup. It's in an old Post Office in the area and they want to keep the ol' gal going.

The case tag shows Model 25-7 Ser.No - HM1466 . International Business Machine Co. Limited, Toronto Canada.

Unfortunately, they can't locate the key to access the slave. I know the Master was not working correctly, but after winding it some and "helping to move the movement", I know it wanted to run and that the slave appears to be working.

The movement's front plate is stamped E13274 on the upper, visible portion, with "International Made in England" just above where the coils are positioned.

A number of the contacts appear to be misaligned, dirty, corroded etc.

So, after cleaning and doing an overhaul (no bushing work required!!!), just some reworking of the wires & terminal ends due to cut strands / missing terminal.

I now have the clock running for over a day in manual mode (I just wind the spring). Seems to be keeping good time.

So, now for my questions:

1. Is there supposed to be grease between the magnetic solenoid "ends" and the brass plate that is bolted to the winding arm? Me thinks there should be to reduce wear & tear and cut down on the noise somewhat.

2. Attached to the anchor arbour, there is a large arm with the barrelled end weight, which contacts the upper left contact assembly. This arm is keeping the contact closed 100% of the time. Is this correct or does it require adjustment so that the contact is only closed when the pendulum swings to the one side?

3. The two roller contacts are actuated by the cams - one set of two between the plates, the other is on the outside of the front plate. Should these be synchronized to actuate at the same time? If not, which one actuated first and how far apart should they be?

4. The 4-pronged contact assembly arm on the lower left. As set up, the bottom contact is closed between 53 minutes (i.e.- 7 mins to the full hour), all the way through to 41 minutes (i.e.- 19 mins to the full hour). These are aprox., as the dial is not presently installed. The top contact closes between 52 to 53 mins (i.e.- from 8 to 7 mins to the full hour). Is this correct?

5. I posted on an other thread about using 2 car batteries to get around 24VDC to run the automatic winding. I may just end up using a couple of LiPo's that I have kicking around instead. How critical is this 24V value? Just don't want to fry the solenoids...

That's it for now, though there may be more...

P1110748s.jpg P1200385s.jpg P1200387s.jpg P1220391s.jpg P1220390s.jpg View attachment 541890
 
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matthiasi

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Dec 3, 2010
344
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Kelowna
www.inhoffclocks.com
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So the movement I have on the bench at present is pretty much identical to the one that JAB60 has in this thread: IBM - IBM Master Clock Power Supply . The one I have does not have the jumper on the top of the case. However, this unit is driven through the electrical box that is permanently installed in the building where it is normally “at home”.

There are a few reasons the clock is running slowly
It could need a service / oil or there is not enough power in the spring to run it
You will need to manually wind the spring by hand to start with
The wind coil / magnet only maintains the spring tension it doesn't wind the clock up enough for what you are doing

Put the clock back as you found it and follow the diagram I have attached
You will need to use a more suitable power supply to run this clock however if the one you have energizes the coil
you could use it for the interim for testing proposes

View attachment 490374
I have this one running on a manually powered spring, outside of its’ case. It has been cleaned etc. and so far, mechanically, it’s running great. I got around 14 hrs overnight and it hadn’t stopped. So, happy on this point.

When I follow Edwardo’s advice from the other thread, I only get a partial success.

I can apply 22.5 volts (6 cell LiPo, 6000mah è so, it has enough juice) across the coil / solenoid and it does actuate and wind the clock. I can't leave the wires there though, for obvious reasons. So I know the coil is good.

When I mount the positive on post 3 (pics above), the negative on the Post for the minute contact, where cables 4 & 5 meet, I do get the trigger every minute, but it dies at the second contact from the top of the “four pronged” points. Is there a wire missing on this unit? Am I missing something – I get the feeling I’m going in a circle… L

I thought that this 4 pronged contact set, being driven by the cam on the hour pipe, was for the duration contact & advance switch.

I would like to be able to test it in my shop to ensure that the contact points etc are properly aligned, before driving the 80 miles to install it… ;)

Kinda hoping that someone would chime in here...
 

matthiasi

Registered User
Dec 3, 2010
344
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18
Kelowna
www.inhoffclocks.com
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OK, so this clock has been working great since the beginning of August.

Now that we had the fall time change (the last one, perhaps, here in BC?), how do we change it here?

I believe the Master clock can be readily turned back an hour. But, how do we change the slave?
Does one have to forward it 11 hours using the fast forward switch in the control box? The control box is the original IBM one...

Me thinks that the exact minute is not that important, as long as the slave is "fashionably late", so that the internal regulation can take place just before the next hour.

Am I missing something?
 

fdew

Registered User
Jul 12, 2007
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Only two ways to set the slave back. Stop the master for one hr, or set the slave ahead about 11 hours.
 

Toughtool

Newbie
Aug 12, 2016
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Panama City, FL
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If you are still working on the clock and needing the question answered, here are my two cents.

1. Is there supposed to be grease between the magnetic solenoid "ends" and the brass plate that is bolted to the winding arm? “

You should not put grease on the armature. The pivot points should be cleaned and lubricated. IBM used a synthetic oil called “IBM #2”. Don't know the equivalent but it looks as fluid as water.
There should be a brass residual between the winding core and the armature. The parts book shows part ref:32, P/N 37653, named Liner-Armature. This is a non-ferrous metal that prevents the core steel and armature steel from touching each other when magnetized, called a magnet seal. If the magnetism is sealed the armature will take longer to release. There is little you can do about the noise.

2. Attached to the anchor arbour, there is a large arm with the barrelled end weight, which contacts the upper left contact assembly. This arm is keeping the contact closed 100% of the time. Is this correct or does it require adjustment so that the contact is only closed when the pendulum swings to the one side?”

This is the two second contact and should be open when the pendulum is at rest (centered). This provides an impulse every other second to: 1. provide the 21 extra rapid “A” pulses during the Master's 59th minute to bring slow secondaries to their 59th minute [so the secondaries can switch their contacts to the N/O “B” contact].
2. To provide the rapid pulses (both “A” and “B”) to all secondaries during an “Advance mode” , when resetting the system for maintenance or time changes.

3. The two roller contacts are actuated by the cams - one set of two between the plates, the other is on the outside of the front plate. Should these be synchronized to actuate at the same time? If not, which one actuated first and how far apart should they be?”

Not sure which contacts you are referring to here. One may be the duration contacts used to hold voltage on a bell or buzzer.

4. The 4-pronged contact assembly arm on the lower left. As set up, the bottom contact is closed between 53 minutes (i.e.- 7 mins to the full hour), all the way through to 41 minutes (i.e.- 19 mins to the full hour). These are aprox., as the dial is not presently installed. The top contact closes between 52 to 53 mins (i.e.- from 8 to 7 mins to the full hour). Is this correct?”

See Photo 2. I believe the lower set is the Stop contact. It is used to pick a relay to stop the “B” pulse from being presented. The top set is the advance contact and it is used if the Run/Advance switch is in the Advanced mode position. This allows the 2 second contact to pulse both A and B lines for advancing all secondaries while the switch is in the Advance position. See the timing notes in the 1938 I.T.R. (IBM) Schematic 1 in my article PDF I posted in the clock article section of this forum.
Development:“A Computer Based Master for ITR & IBM Minute Impulse Secondary Clock Movements”

5. I posted on an other thread about using 2 car batteries to get around 24VDC to run the automatic winding. I may just end up using a couple of LiPo's that I have kicking around instead. How critical is this 24V value? Just don't want to fry the solenoids...”

I recommend you use a 24 volt DC power adapter to run the clock, similar to a computer notebook power supply. They run about $10 to 15 dollars on Amazon for 3 amps. The winding magnet on a model 25 Master clock movement uses 0.132 amperes @ 24 volts (or 0.273 amperes @ 12 volts). The power from an IBM unfiltered rectified output of their transformer should be 24 volts (RMS @ 60 Hertz), but will be as high as 36 volts peak voltage. The service manual says the magnets are designed to operate on ¾ rated voltage.
Normally the master movement is wound with each “A” pulse and there are 80 of these per hour. 60 pulses per hour should be enough to run the clock but if there as a power outage, for say, four hours, the master may not get fully rewound and therefore will change it's speed.

Joe Fox KD4MS

Reference the IBM schematic.
Schematic 1: Page 16, from ITR Service Instructions Number 230, April 1, 1938. Reprinted by
permission from Reference Desk, IBM Corporate Archives, Route 100/CSB, Somers, NY, 10589
Article PDF found here:
KD4MS/A-Computer-Based-Master-Clock-for-ITR-and-IBM-Impulse-Secondary-clocks

Photo2.jpg Schematic1.jpg
 
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