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A close-up of the IBM 1620's distinctive control console. The lights and rotary knob on the top panels were used to debug programs. The lights and buttons on the lower right were the operation controls. The toggle switches on the lower left were used to modify program execution.

This photo shows the wide carriage version of the console typewriter for the IBM 1620 Model 1. Note that a standard 1620 console typewriter had a narrow carriage and was recessed in the system unit's tabletop. This typewriter is on a separate stand as was done with the IBM 1710 Process Control System.

This is the reader portion of the IBM 1621 Paper Tape unit. It was the only auxiliary input device available on the earliest 1620 systems so each of those systems had one. Later, when a card reader was introduced, paper tape became less common.

This is the punch portion of the IBM 1621 Paper Tape unit. It is housed in the lower bay of the cabinet. You have to open the lower bay door, swing out the tape punch and open it's lid to access the unit.

The next series of pictures show the progression of opening up the IBM 1620 computer system. Here's a look at the 'B' gate seen right after opening the back of the cabinet. Note the two metal panels which cover the card cage to direct the air flow for cooling.

Here's another shot of the 'B' gate covers (taken from a slightly different angle) on an early production 1620. In this machine, separate plastic blue and black panels individually cover each row of cards.

Here one of the two metal covers has been removed showing one card cage with 10 rows of up to 28 SMS cards each.

Here the other metal cover has been removed exposing all of the 'B' gate of SMS cards.

Swinging open the 'B' gate shows the backplane wiring of both the 'A' and 'B' gates. The backplanes were wired by a standard Gardner-Denver wirewrap machine. Notice the back of the core memory unit in the upper-right corner of the 'A' gate.

Swinging open the 'A' gate reveals more SMS cards. The core memory unit is now in the upper-left corner. The right-most card cage is still covered with its metal panel for cooling.

Looking into what's left in the main cabinet. In the top of the picture is the back side of the control console. Below that and to the left is the +48v power supply. To it's right is an open space for the 'J' gate which would contain the disk interface logic if that option were installed. To the far right is a bank of capacitors which are connected to the (unseen) main power transformers. Also not visible are the other power supplies which are in the front of the cabinet.

Ending this photo sequence is a shot of the 'C' gate. This gate contains relays and other circuitry for primarily controlling the console typewriter.

The IBM 1620 was built using approximately 1000 SDRTL SMS cards of 49 different types. SMS was an internal IBM standard (specifying card form factor, backplane wiring, logic card families, etc.) used in all their computers of that era.

This is a remote control used by customer service engineers. With it they could work in the back of the machine or on one of the peripheral devices and still control the running of the diagnostic program.