# ITR slave clock power

#### Ed O'Brien

NAWCC Member
I have a self-winding International Time Recorder clock and want to obtain and add one or more slave clocks. The master plugs into 120VAC, and I know the coils for the self-winding system are 12-volt. How do I determine the electrical requirements for slave clocks?

#### Toughtool

##### Newbie
This is a table of measured dc coil resistance and IBM published current requirements for 12 and 24 volt secondary movements listed. Sorry for the format errors but this site reformats my table automatically which makes them hard to read. The correctly formatted tables are in my PDF article at KD4MS/A-Computer-Based-Master-Clock-for-ITR-and-IBM-Impulse-Secondary-clocks
See also: Development:“A Computer Based Master for ITR & IBM Minute Impulse Secondary Clock Movements”

The article has other information about these movements that may be helpful. The posted schematic is how to wire the secondaries. Where you see 24 volts, substitute 12 volts. The schematic is the same for 12 volt or 24 volts. Your mainspring wind magnet is attached to A and C and will draw 0.273 amps. The power supply shown would be your 12 volt master clock power supply, not an external power supply like my schematic shows. Your clocks C line will be +12 volts DC. Joe

Type Description 12 Volt 24 volt 12V to 24 V Conversion Resistor
25 Master's Winding Magnet .273 amps .132 amps 43 ohm 5 watt (actual 3.36 watts)
25 Impulse Accumulator .280 amps .140 amps 43 ohm 5 watt (actual 3.36 watts)
805-2 Program Magnet .545 amps .279 amps 22 ohm 10 watt (actual 6.54 watts)
561 Indicating Clock Movement (20V) *.028 amps. Use R1, 150 ohm 1 watt resistor to (*20 volt coil measured with 20V applied: I=28 mA) convert coil from 20 to 24 volts.
561-2 Indicating Clock Movement .050 amps .024 amps 240 ohm 1 watt (actual .6 watts)
563-2 Indicating Clock Movement .333 amps .171 amps 36 ohm 5 watt (actual 3.9 watts)
565-2 Indicating Clock Movement .170 amps .085 amps 68 ohm 2 watt (actual 2.1 watts)
569-2 Tower Clock Movement .050 amps .024 amps 240 ohm 1 watt (actual .6 watts)
_______________________________________________________________________________________________

Table 2: Table of resistors (R1) required to convert from 12 volt (and 20 volt) coils to 24 volt operation.

Type Year Resistance Coil Voltage Measured current @ 12V Measured current @ 24V
561-2, 1948 245 ohms 12 Volt 0.049 amps 0.097 amps (Over current!)
561-2, 1930 964 ohms 24 Volt 0.012 amps (Under current) 0.024 amps*
565-2, 12 Volt (I do not have one to measure.)
565-2, 1955 244 ohms 24 Volt 0.049 amps (Under current) 0.097 amps**
________________________________________________________________________________

Table 1: My 24 volt coils connected with 12 volts did not rotate the armature fully. Some may only move a little, if at all.
* Correct reading per table 2 for this model at 24 volts.
** This measured 24 volt reading is 0.012 amps higher than the current listed in IBM's Published Table 2, P9.
Also this table may be useful.

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#### Ed O'Brien

NAWCC Member
Thanks Joe. What a remarkable resource you are.

Ed

#### Toughtool

##### Newbie
Ed,
Thanks. I'm not sure of what you have on your test bench so I though I would try and explain what I am thinking. From your question I think you are still a little confused about your 12 volt power supply.

When IBM sold time equipment to their customers, they sold them a customized system tailored to their specific needs and requirements. Unlike a visit to Best Buy or Micro-center (no affiliation) where a system fits all and they are all the same. The result is there maybe hundreds of different schematics from years of manufacturing and sales, and the chances of finding a match to your specific system are nearly non-existent. That being said, the available schematics can be very helpful. You just have to figure out what you can use and what you can not use.

There are basically two types of systems. One is a large master clock system with it's master clock and case and a separate cabinet (or cabinets) that hold transformers, relays, rectifiers, switches, programming unit, and wires. The other is the smaller systems that were more generic, a master clock with the transformer, relays, rectifier, switches, programming unit, and wires, all inside the clock case. These systems were sold to customers that needed only a minimum simple system. A good example is school systems. They all needed a bell ringing programming device and a secondary in all the class rooms and offices but no accounting or time recording devices that add to the complexity.

So, a photo of your setup would be very helpful. I have posted three schematics with a ellipse drawn around a somewhat standard terminal identification. Usually there is a terminal strip on top of the master clock case with labels that I have indicated in the schematics. The schematic of Jim's clock for example, is a master of the first type, only the contacts on the master movement and the terminals on the top of the case. The rest of his schematic (to the right of the terminals) is my design, to create a master control system to run his secondaries. This was needed in his case because he did not have any equipment cabinet, just the master.

The third schematic I found on a post here on NAWCC. It most likely is of the second type system, a self contained system with the controls inside the master clock's case. So in your case, Do you have just the movement running on your test bench? If not can you get the case and marry the two? Joe

Oops, I missed a couple of terminals on the last schematic.

View attachment 604434 View attachment 604436

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#### Ed O'Brien

NAWCC Member
I'll be back at customer's location in the next day or so and will take some photos.

Ed

#### Toughtool

##### Newbie
OK Ed,
Just to let you know, I have verified my newest project and in a timely manner for you. You can now look for any 12 volt or 24 volt three wire impulse secondary and use it on the system you are working on. Here is a preview.

ITR / IBM Slave Clocks: Using either a 12 volt or a 24 volt, or a mix of each
It really doesn't matter if you buy a 12 volt or 24 volt secondary for your International Time Recording (ITR) or International Business Machine (IBM) master clock system. This article will show you how to wire and use any combination of master or secondary clocks.

You can have a 12 volt master clock system or a 24 volt master clock system and mix and match secondaries any way you want. I have already discussed a way to convert a 12 volt secondary to work on a 24 volt system; I now offer a way you can use that 24 volt ITR or IBM secondary on a 12 volt master clock system. So if you just happened to make an affordable and an adorable Impulse secondary find, it does not matter that it has the wrong voltage for your master clock system.

Wiring an ITR or IBM, 12 volt secondary to a 24 volt master clock system:

Wiring a 12 volt DC secondary to work on a 24 volt DC master clock system is as easy as adding a single resistor in series with the C connection and the coil's C terminal. The current limiting resistor consumes the extra 12 volts, leaving the remaining 12 volts for the Impulse Secondary's coil. The system sees a total load of 24 volts and will be happy. (12 + 12 = 24 volts) See the resistor conversion table below.

Type Description__________ _________ 12 Volt____________ 24 volt___________ 12V to 24 V Conversion Resistor
25 Master's Winding Magnet________.273 amps_______.132 amps_______ 43 ohm 5 watt (actual 3.36 watts)
25 Impulse Accumulator___________ .280 amps_______.140 amps_______ 43 ohm 5 watt (actual 3.36 watts)
805-2 Program Magnet____________.545 amps_______.279 amps_______ 22 ohm 10 watt (actual 6.54 watts)
561 Indicating Clock Movement (20V)*.028 amps. Use R1, 150 ohm 1 watt resistor to (*20 volt coil measured with 20V applied: I=28 mA) convert coil from 20 to 24 volts.
561-2 Indicating Clock Movement____.050 amps_______.024 amps______ 240 ohm 1 watt (actual .6 watts)
563-2 Indicating Clock Movement____.333 amps_______.171 amps______ 36 ohm 5 watt (actual 3.9 watts)
565-2 Indicating Clock Movement____.170 amps_______.085 amps______ 68 ohm 2 watt (actual 2.1 watts)
569-2 Tower Clock Movement_______.050 amps_______.024 amps______ 240 ohm 1 watt (actual .6 watts)
_______________________________________________________________________________________________
Table 2: Table of resistors (R1) required to convert from 12 volt (and 20 volt) coils to 24 volt operation.

Wiring an ITR or IBM 24 volt three wire Impulse Secondary to a 12 volt master clock system:
For those who have a 12 volt master clock system and want to install and operate a 24 volt secondary, you only need to purchase a small device called a DC to DC Boost converter. Making a 24 volt coil work with a 12 volt system is a little more involved than the resistor conversion described above, but not by much. We need to convert the 12 volts (the C line) that is available to the 24 volts that the secondary is designed to operate with. Through the marvel of electronics there is now available a very small and economical voltage converter called an MT3608, DC to DC Boost converter that will work just fine. Economical means from around \$1.50 to \$5.00 each, and up, depending on where you buy. I have chosen the MT3608, DC to DC Boost converter for several reasons. The device is available online from many sources. The 1.2 MHz operating frequency of the device allows for a very small footprint and can be hidden inside the secondary's movement cover and will be out of sight. This device does not modify the movement, except for an additional wire, so the original movement's wiring is not altered permanently. The device operates at around 91 percent efficiency so it saves energy. It's 2 amp maximum output current (more like 1 amp in reality) is more than enough to drive any impulse device, such as a secondary, a master's winding coil or program unit's impulse coil.

Referring to my schematic, the positive input of the converter connects to the C line [which is always at 12 volts] and the converter's 24 volt positive output is connected directly to the secondary's C terminal [to the coil]. Since the device's negative Input is internally connected to the negative Output, this connection is made only to the operating strap of the secondary's A/B cam operated contact set, with an additional wire. This connection is not grounded until an A or B line is grounded by the master relay in the master clock's control circuits, so the DC to DC Converter device needs to be isolated. Once every minute (except the 59th minute), when the A or B line is grounded, one of these pulses will ground the converter and make it active, converting the 12 volts to 24 volts and causing the 24 volt coil to energize for the duration of the pulse. Most of the time (59 seconds of every minute) the converter will not be grounded because the A or B lines will not be grounded. So therefore the converter will not be powered ON.

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#### Ed O'Brien

NAWCC Member
Again Joe, thanks. Now, to find three or four of the slaves. Concerned about purchases from Ebay, as some units are not as they should be. In response to a question about one I was told it had been retrofitted with a quartz movement. Others could not answer as to whether the unit was complete or operational. Prices listed seem too high to receive a piece of junk in the mail.

Ed

#### Toughtool

##### Newbie
Here is a link to the secondary operating with the DC to DC converter.

My tips on buying an IBM or ITR minute impulse secondary movement.

Worried about an ebay purchase? Ebay.com is a good source, they are not the only source. A plus of course is the paypal purchase protection from scammers. So look at other sites too. IBM made these movements to last a very long time. I have not seen a bad one. I did get one with a missing (non-standard) screw so I had to make one to replace it (movement made in 1928). My take is to limit the amount I would pay to the amount I can stand to loose if it is a bad deal. So being on a fixed income, for me the limit is under \$100, unless it is an exceptional nice looking secondary. About the worse risk you can expect is some idiot seller wanting to see if it runs by connecting 120 Volts AC to a 24 volt DC coil and burning it up. An Ohm meter reading will verify the coil is good or bad. However these coils are rewindable, but this can be a tedious process. I am not sure of rewinding a 565 type movement.

Study the movements you see listed for sale and learn the differences. There are several model types that will work on an IBM minute impulse three wire master clock system. I have photos of some of these movements in my article. While the mechanical movements may look different, the other side will still give you the time. I am more interested in the non-second hand versions of IBM movements, called minute impulse secondaries. While the AC synchronous movements have a second hand and a method for synchronizing with a master clock system. My electronic master clocks and probably the master clocks manufactured before the 1950's do not support this synchronization method without extra logic in the master control circuits. I have not seen a circuit for this and I'm not very familiar with this correction method. They may be using the master's duration contacts for this pulse.

There are three types of system controls. A two wire plain impulse, a three wire self correcting, and a two wire self correcting where the polarity of the pulse is reversed and the movement uses a diode to steer the current for corrections. From a schematic of this circuit, it seems to me that the movement will work if it is rewired as a three wire movement and the diode is removed.
1. Look for a movement showing the covers off of the movement, and see if it has missing or damaged parts. Determine if it has converted to a quartz movement. If so, avoid this movement. You should see three wires coming out of the unit and it should have an A/B contact set. Original wiring color code is Green for “C”, White for “A”, and Black for “B”.

2. Having a readable label showing the voltage is a plus but not absolutely required. My article describes how to determine the voltage of an unknown secondary. Also, we can now mix and match voltages.

3. Glass is replaceable, even the domed glass of the type 565-2 , 1950's models. Although there is an expense in replacing it, don't let it kill an otherwise good deal.
I have posted five different movements but I know there are more. Joe

NAWCC Member

#### Toughtool

##### Newbie
Ed,

That's a nice looking master clock! That one is a little more complicated than the small school masters with a simple bell program. Your program unit has a lot of disks and there are two circuits for bells. Probably why you have a duel duration contact set on the movement. Hope you got their end play problem fixed.

Your case has the multi-tap transformer in the upper right and the rectifier mounted below. I also notice the movement's contacts are mounted on what looks like a phenolic board. This clock must be an early one. One transformer tap will be going to the bridge rectifier that is connected to line “C” and terminal 1. They usually “make and break” the primary (AC) side of the rectifier. Arcing of the contacts is less when switching AC.

In your photos, I see a problem with the advance relay. The contacts look burned, which is not surprising, and there are some non-IBM wires attached to it. I don't see the master relay.

Have you remounted the movement in it's case or do you still have the case on the workbench?

#### Ed O'Brien

NAWCC Member
It is mounted but I have access and can remove it. In fact, I probably will next week since, when I went in to take the photos it would not run in manual wind. I had wound it and it ran out the wind, so I am thinking the little we did - move it onto a 4-wheel dolly for access and me adding the missing screw - created some issue. I had to replace bushings front and rear on the center arbor, and suspect I may have an issue with end shake. I did note that I could manually make the winding contacts connect, but they were not operating normally. Felt I may need to close the gap, but it sounds like you have seen something else.

Ed

#### Toughtool

##### Newbie
OK, Ed, next time you are at the clock, wind it and get it running. Listen for the minute impulse relay to click each minute. It should operate every 00 second of every minute (plus 21 more every other second after the 59th minute). If you are not getting the master relay operating, troubleshoot why. If the relay is operating, look for a problem with the master relay's contacts. Clean and burnish them if needed. Note: the wind magnet wires are not connected in my photo. I took the photo before I connected them.

You may want to make a temporary aid by connecting an LED and a 1500 Ohm resistor across the wind magnet coil. Then you can see if you are getting an "A" pulse. The Anode to the plus (+), the resistor to the Negative (Ground) side of the coils terminals as in the photo. If the LED is too dim, reduce the resistor to 1000 Ohms. You can do this with the "B" pulse too. Remember the terminals A and B on the movement go to ground so if you connect a couple of LED detectors to C (your + 12 volts), you can connect the resistors to A and B.

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#### Toughtool

##### Newbie
Well, this is kind of embarrassing! My new idea with the 24 volt secondary has a little problem and I am apparently premature in it's announcement. The DC to DC converter worked great for about 12 hours then failed. I am working on a fix but wanted you and everyone to know there is a problem. I think it is the old enemy, "inductive kickback", so when I get some new parts I will be back I hope with a fix. Joe

#### Toughtool

##### Newbie
I noticed that my last post was left in the air. So an update. I added a protection diode, a 3 amp, 1000 Peak Inverse voltage (at \$7.00 for Qty of 50) to reduce the effects of the induced Back EMF of the coil on the regulated output of the converter. This is mounted across the output of the DC to DC converter, cathode to the + output, anode to the operating strap. (See the attached schematic) I have been running the secondary for the last seven months and it has been working just fine. Problem solved.

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