RadioShack Chess Champion 2150L

  • Year: 1992

  • CPU: Hitachi H8/325 - 8MHz [8-bit Single-Chip*]

  • RAM: 1KB*

  • ROM: 32KB*

  • Programmer: Julio Kaplan

This chess computer had a fault in the LCD: information was missing on the bottom line, where the most important data is shown.

Detail of the malfunction:

In the central area of the bottom line, the information is displayed incorrectly.

By applying considerable pressure with a finger, the problem disappears.

I proceed to disassemble it. To do this, 6 screws have to be removed, and then the bottom cover has to be pivoted over the part of the power connector, taking care not to break the plastic tabs.

It's possible to remove only the Display module thanks to the length of the flat cable that connects it to the motherboard, but I decided to remove it all to be able to work more comfortably, and to take the opportunity to do a general overhaul.

First of all, the connector on the sensory board has to be removed, then all the wires have to be unsoldered, and finally all the screws holding the various PCBs have to be unscrewed.

Repairing the Display module:

Elastomeric connector.

The signal passes from the printed circuit board (PCB) to the liquid crystal display (LCD) through conductive rubber bands (elastomeric connectors), as shown in the diagram above. In order for the module to function properly, these elastomeric connectors have to be pressed together uniformly in a sandwich structure. The problem in this design is that two of the four fastening screws, those at the bottom, are too far apart. This causes the PCB to warp over the years, so that the elastomeric connector makes poor contact in the middle.

In this picture you can see how the PCB is warped.

I use a remnant of a fibreglass PCB to make two reinforcement pieces.

The reinforcements are fibreglass, with copper on one side. I orient them with the copper facing upwards so as not to damage (or short-circuit) the PCB tracks.

I insert a spacer in the central area to straighten the PCB and maintain a constant pressure in the central area.

And now assembling the components, in reverse order:

It is important to align the contrast knob correctly with the potentiometer on the PCB.

Contrast potentiomenter.

Finally, the wires are soldered and the sensory board is connected:

And the chess computer is now ready to close, and test: