NCR EM-D2 card reader

[MattisLind]

A while ago I got this NCR EM-D2 card reader.



It is from around 1967 and is OEM card reader that NCR sold to various other computer vendors. DEC apparently called it CR01 in this document and CDC used it in their 200 series user terminal as well. This particular reader had been used in a bespoke system that counted cowhides used by a company called Kontrollhudar. I got the reader from the man who designed the system in the late 1960-ies when studying his second year at tekniskt gymnasium.





I have been going through the machine and cleaned it up and removed old grease so now all parts move freely. The problem that remains is to understand how to interface the thing. There are some transistors and relays inside creating some kind of logic that controls the operation of a solenoid. Since there is no transformer in there it is very likely that voltages for the control is supplied by the customer equipment. But I have no description on any type of interface to this card reader. Since I have the cut off cable and the connector that used to interface it I am quite sure where 220 VAC is entering the machine. But that mostly runs the 1/40 HP GE motor and not much else.

Around February 2021 there was a manual for sale on Ebay. Not sure if it ever sold. If anyone that happens to see this post have this manual I would be very interested in a scan of it. This seems to be the maintenance manual which would be extremely useful to have...

 

[Al Kossow]

I tried to find a copy of the OEM manual when you first got this, but all I could find were a few interface manuals for computers that interfaced to it, and a
unrelated OEM paper tape punch manual.

 

[MattisLind]

I know. Thanks for trying to find docs! I am publishing here mostly to see if someone in the future search for it and finds it. I have tried to track down more info on the CR01B and CR01C PDP-7 and PDP-8 interfaces respectively. It appears that the 34D option backplane also contains the CR01C interface option.

 

[MattisLind]

I pinged the old man that gave me this reader once more a couple of days ago and he searched through his old papers and today he found something. The most important piece of paper that I surely needed if I ever going to be able to get it working again: The electrical diagram for the control logic and what the connector pins are. Hooray!





What are diodes with round ring and a lambda? Zener? No, when I think of it they are probably photodiodes. There are a slot wheel in the design. Interesting set of supply voltages. -4V, -10V, -21V and +10V...

Now I can get a bit further on this project creating a power supply and start interfacing to something. For example my PDP-8/L.

He also sent a few beautiful hand drawn diagrams of his interface design with the old transistor symbol that was used in Sweden (and Europe) before adoption of the EIA standard symbol.

 

[MattisLind]

Here is the inside view of the cleaned up NCR EM-D2 reader. A lot of grease and gunk in there. And also an old Danish 25-öring (coin).



Basically there are two solenoids and a 1/40 HP GE motor that drives this unit. L201 pulls a lever that make it possible for the card to enter the unit that senses the cards. The same movement also pulls card (white plastic piece that is close to the C201 capacitor. L202 unlocks the feed wheel to feed the card into the sensing unit. I think that the idea of having two encoder wheels is that one is for clock pulse generation and the other one can be pulled loose and marked somehow to mark the columns that need some kind of special action in the host-equipment, so that a counter won't be needed. SR201 senses that a card is pulled into the sensing unit. SR205 (or is it SC205) is senses the position of the lever that pulls in card and raises the feed-wheels in the sensing unit. SC203 is the out of card sensor effectively turning off the motor. I am not really sure what purpose of the cam wheel switches SC201 and SC202 are, but they are probably synchronising various events in the reader.

The arm in the middle sitting on the cast iron gear housing is used to move a sliding mechanism on the sop-cover that picks the hard from the hopper and feed them on the area where they are pulled into the reader unit.




The star-shaped wheels are feeling the punched holes and actuates 12 switch fingers to make or break contact as the card is feed through.



The electronics of the reader. The big transistor is for driving the L202 solenoid. Then there are amplifiers for the opto-diodes. There is also a big 4500uF capacitor in the in the L202 drive circuit. Haven't really understood the purpose of that one. Some kind of timing circuit?

The belts in the units is a 2L140 V-belt and a 130XL025 timing belt. The AC capacitor is a GE 1.5uF 370VAC cap. Very likely a PCB containing cap since the machine was built before the PCB ban.

The V-belt has proven to be impossible to find in Europe while the timing belt is readily available. Unfortunately the US companies want to charge 100USD for shipping a 5USD belt to Sweden. Highly annoying. Getting a 1.5uF oval capacitor is also impossible in Europe while there are available in the US.

Speaking of rubber item. The condition of the rollers is not perfect: They are all rather hard. We'll see if they need to be replaced to get it to work properly.

A good thing was that I got the 50 pin Winchester connector that ones belonged to the now scrapped cow hide counting system system.