IBM System 370 Model 155 (3155)

The Model 155 certainly had a lot of lights on the operator console.

Several cloth and paper tags are on the inside, most no longer readable. However, one tag says January 7, 1971. Here is what a complete Model 155 looked like back then:

This wonderful old machine panel lives again. Approximately 500 of its 567 lights flash, driven by PIC16F877 microcontrollers buried in a control box inside the walnut cabinet. (Not all lights worked, depending on the position of the rollers.)

Click here to see a floor to ceiling shot of the 3155 and cabinet ...

Watch the 370 Model 155 in action with this short WMV.

The original lamps draw too much current and create too much heat. To preserve the panel and plastic lamp holders, newer bulbs were inserted into the original bulb holder assemblies. While time consuming, the result is cool operation which will preserve the panel for many years to come. The original bulbs draw more than 100ma at 5V (which is probably lower than they were intended to be driven). Newer 7361 lamps draw only 50ma when driven through ULN2803 darlington arrays and 5V supply (accounting for some voltage drop through the transistor drivers). Other projects in the gallery use LEDs inside the original lamp holders, resulting in even less heat and longer life (although incandescent 7361's are supposedly 10,000 hour bulbs).

Several programming tricks make the 3155 panel seem to be working again. Two of the 16F877 microcontrollers coordinate their output to make the center of the panel seem to be churning away on a hard problem, while other 16F877s are programmed to make other parts of the panel do their own thing. It's impressive when turned on, but no video is available (yet).