DIYbanter - View Single Post - ADM-3A Wonky Until Warm

Rob[_40_]

Ralph Mowery wrote:
In article ,
says...

On 19.06.20 9:02, Tom Lake wrote:
I have an ADM-3A dumb terminal and when I first turn it on the display is squashed and the top line is mangled. After five minutes or so the display looks OK but is a little jumpy. After a few more minutes, the display is rock-solid and stays that way until the next time I turn it on cold. If I turn it off back on, the display
is still fine as long as I don't let the ADM cool off first. Does anyone know what the problem might be? What to look for?

Check for bulging caps. they are failing, and work best at a bit higher
temperature.

I would also check for bad capacitors. Instead of the freeze spray, try
heat. I have a hot air rework station and the heat wand has a very
small nozzle where I can heat a small portion at a time.
The heated capacitors usually make the problem go away very quickly when
the device is first turned on.

In a device of that age, start by replacing all larger caps (physical
size of 12mm/.5" in diameter and larger) and re-solder all largish pins
in the circuit boards (inductors, transformers, connectors).

When there still is a problem after that you can use heat/cold to hunt
for a smaller failed component.