Threaded Mode | Linear Mode

teenix · (This post was last modified: 03-30-2024 11:31 PM by teenix.)

The display board in the image looks pretty normal for its age.

Because the display is multiplexed, it is most likely that digit 1 has problems with some LED segments.

It is possible the problem lies in the IC's on the CPU board, but I'd still guess the display.

If you have some basic electronics experience, you can test the segments, by using a 3-5V supply and a 1K resistor and some test leads or wire. The test will require opening the calculator and removing the display module.

With the display removed from the calculator, looking down at the top lens with the pins on the bottom, pin 1 is on the left. Pin 16 is the cathode pin for the digit 1. Connect this to -ve on the power supply.

Connect the 1K resistor in series with the +ve supply.

Touching the unconnected end of the resistor on the following pins should light the corresponding LED segments.

3 Decimal Point
4 seg C
5 Comma
6 seg E
17 seg D
18 seg G
19 seg F
20 seg A
21 seg B

If any of the segments do not light, it is probably not repairable.

cheers

Tony