I have an old TRS-80 model 100 that has not been used for the last
several years. It worked when I put it away. I recently resurrected it
to do some simple BASIC programming. I was amazed to find that all of
the old RAM programs were still present! (I did replace the batteries
from time to time while it was in storage.)
The machine still worked. However, the screen tends to flicker slowly
from its normal density to being very dim. This improves somewhat *
is still present when it is plugged into its AC power supply. (This
charges the small nicad battery that maintains the memory.) However, the
flicker it never completely goes away, and gets worse as the main
batteries become used up. However, even when the screen is dim the
information on the screen is accurate.
Here is what I have done to try to solve this problem:
Voltage of the nicad battery is okay when measured with a volt meter.
Removing all removable chips (memory, ROMs, etc.), burnishing their
contacts and reinserting.
Checking all cables and wires and plugs going to and from the screen.
I wondered if there is some capacitor that has aged and is affecting the
screen voltage. Any suggestions would be appreciated.