Thursday, June 5, 2025

Disconnecting wiring to remove power supply box from 2501 card reader

WOULD BE VERY INCONVENIENT TO TEST PS WHILE INSTALLED UNDER READER

The power supply and power control box sits in the bottom cabinet of the 2501 card reader, which would require me to lay down to reach inside to properly test it. Making this even more challenging, as of yet I do not have the wiring diagrams and schematics for the 2501; I am hoping I can find someone with a copy that can send me a scanned image. If not, I will need to reverse engineer the wiring to complete my restoration and testing, which will be vastly easier if I can put the box up on the workbench. 

MULTITUDE OF WIRES BETWEEN THE PS BOX AND VARIOUS OTHER PARTS OF 2501

Some wires come to the PS box and are connected to terminals. Others are wires that enter/exit the box and are connected inside. There is the possibility of labeling the wires going onto terminal blocks so they can be reattached correctly. Wires running directly inside the box must either be disconnected inside the box or at the other end where they connect to the reader mechanism or logic gate. 


Two terminal blocks on the outside are the simplest aspect of disconnecting the box for removal. There is a usage meter power box on the side of the main PS box which has three sets of wiring running into it - for AC, control signals and drive power for the usage meter itself. A cable runs up to the AC motor for the drive mechanism. The incoming AC power that arrives on cables from the IBM 1130 system is fed through a cable clamp inside the PS box. 

The IBM 1130 delivers 115VAC, 208/230VAC, and 7.5VAC into the PS box. Other wires in the power cable from the 1130 run directly to the logic gate to feed it +3, -3 and +6V. The PS box itself will produce 24VDC and 2.5VDC for use within the 2501. In addition, the usage meter box has its own power supply to produce the 41VAC to spin the usage meter. 

TERMINAL BLOCKS 2 AND 3 LABELED AND DISCONNECTED

Terminal block 3 delivers the 2.5VDC generated by the PS box up to a distribution box on the top of the reader where it powers the main lamp used to read holes in the punched card as it moves past photocells. Terminal block 2 connects many control circuits inside the PS box to the rest of the machine. 


The 24VDC supply is controlled by a relay inside the box before it is passed along to control the various solenoids for picking and feeding cards. The wires from the relay pop out alongside TB2 and run to the logic gate. 
relay controlling 24VDC

IBM laces their cables very carefully so that the wires for each screw on a terminal block are easy to distinguish as they fall naturally right at the point where they should be connected. 


USAGE METER PS CONNECTIONS UNHOOKED

Two thin yellow wires bring the control signals to the usage meter, driving it to accumulate usage hours when the reader and/or the IBM 1130 are busy. They were connected to a terminal block inside the meter compartment on the side of the PS box. Another pair of wires (red and black) attached to the terminal block runs from the meter box up to the top of the 2501 to connect to the usage meter. 


Lastly, some 208/220VAC wires from the PS box run into the meter compartment and hook to a second terminal block feeding the transformer primary. I unhooked and labeled the logic and usage meter wires, but left the AC connections attached. The meter compartment was unattached from the PS box but will be brought to the workbench along with the PS box. 

AC INPUT WIRING BEING DISCONNECTED

The 115VAC wiring - not, neutral and ground - run directly to a convenience outlet but nowhere else in the machine. I removed the convenience outlet from the PS box and labeled the wires that had been attached to it. 
Plastic box housing convenience outlet

The 208/220VAC consists of two hot wires that are connected within the PS box somewhere behind the four large screw-in fuses. They must also run to the contactor, circuit breaker and cable up to the main reader drive motor. I have yet to find and disconnect these. 

rubber sleeves over terminals on fuse holders

MOTOR POWER WIRING MUST BE DISCONNECTED AS LAST STEP

Until I look more closely, I don't know if this wiring must be removed inside the PS box or up at the motor on the top compartment of the 2501, but it will need to be disconnected before the PS box is fully independent allowing it to be removed from the 2501. 

Motor wiring, 2.5VAC wiring and other signals go up

TERMINAL BLOCK 1 INSIDE PS BOX ROUTES AC TO VARIOUS COMPONENTS

There is a terminal block inside the PS which interconnects various relays, power supplies, transformers, fuses etc. This will require reverse engineering if I can't find a copy of the IBM diagrams and schematics. 



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