Reinstalled the power box inside the 2501 card reader

INSTALLED BACK IN BASE OF THE READER

The power box fits on top and bottom rails inside the card reader enclosure, on the right side. I installed it and replaced the cover. 

The power box is connected to several other parts of the card reader. I describe a bit about the type of connection and how it is made in the sections below. 

AC CONNECTED TO UTILITY OUTLET AND POWER BOX

The 2501 card reader is connected via two thick cables to the IBM 1130 system. One of the cables carries data signals while the other brings power to the 2501. The power cable is split out inside the 2501 enclosure into an AC and a DC connector. The DC connector brings the SLT logic power rails from the main system - +6, +3 and -3V. The AC connector brings 230VAC, 115VAC, and 7.5VAC for the lamps on the control panel. 

The AC connections for the lamps are routed separately, but the other AC voltages are connected through a bundle of wires clamped at the bottom of the power box. The 115VAC is connected only to the utility outlet - that outlet has power even when the 1130 system is powered down, typically used for oscilloscopes or other repair related equipment. The 230V is used to drive the motor and to produce some additional AC and DC voltages used in the card reader. 

USAGE METER CONNECTED

A usage meter records the time that the 2501 is active; IBM in the past had rental plans where users were charged based on usage of the computing systems. A power supply on the outside of the main power box produces the 41VAC that turns the usage meter and contains the control circuitry to start and stop the meter. A pair of wires run from the usage meter on the top of the card reader down into the usage meter power box. Another pair of wires runs from the usage meter power box over to the SLT card cage, to detect when the reader is active or idle.

LAMP POWER FOR READING AND CARD DETECTION

A pair of lamps are used inside the 2501. One of them shines onto a photocell that detects when a card has entered the pre-read station and is available for a read or feed operation. The other shines through fiber optic cables to the 12 card row positions to illuminate 12 photocells underneath the card if there is a hold punched in the card at the current column. 

Two pairs of wires are connected to terminal strips on the outside of the power box, one each for the two lamps. 

MOTOR POWER

The main motor that drives cards through the machine is connected via a cable that runs from the top of the reader where the motor is attached down to the power box. The power box will turn on the motor when a read, feed or non-process run out (clearing cards from the machine) is requested and keep it running for 15 seconds. If a series of reads take place the motor thus stays running continuously but is shut down when idle for 15 seconds or more. 

SIGNALS AND CONTROLS BETWEEN LOGIC GATE AND POWER BOX

The power box produces 24V to activate various solenoids that feed cards inside the reader; the power is connected from the power box to the logic gate which in turn sends the power to the solenoids. A number of control signals are connected between the logic gate and the power box. For instance, the signal to turn on the motor is sent to the power box and the timer indicating that 15 seconds has not elapsed is sent back to the logic gate. 

NEXT STEPS - TEST THE LAMPS, PUSHBUTTONS, MOTOR AND SOLENOIDS

Before I connect the 2501 to the 1130 I will check out the indicator lamp circuits. These run on 7.5VAC and will illuminate when +3V is present on the control wire or be dark when the control wire is at ground. I can isolate these and test them. The circuits use an SCR to drive incandescent bulbs. Generally the bulbs are the most likely to have failed.

I will also verify that the various pushbuttons have good connectivity and operate properly. They may need to have oxidation cleaned out. 

Once all of the above is complete, I am ready to apply power to the 2501 from the IBM 1130 and begin some testing. The NPRO button triggers a non-process run-out, meaning it feeds cards that may be inside the reader to flush them out to the stacker but does not feed cards in from the hopper. The START button will trigger a feed cycle, moving a card from the hopper into the reader. Both of those allow me to verify that the motor starts, stays on for 15 seconds without further activity, and that the two feeding solenoids are activating.