VT220 Keyboard Error 4?

Kevin Handy kth at srv.net
Sat Oct 4 15:57:37 CDT 2008

tiggerlasv at aim.com wrote:
> I tend to look for the simpler explanations first.
> If your keyboard was previously working,
> the first place I would check is the MMJ 
> on the back of the terminal.
> I've seen everything from malformed pins,
> to corrosion, to spider webs, to dead bugs
> inside RJ12 / RJ45 connectors.
> Another point of failure is the?MMJ on the keyboard cable;
> you can try removing that, and re-crimping it.
The keyboard doesn't use a MMJ connector. It's a regular
RJ connector. Try replacing that cable first, it has RJ
connectors on both ends for the LK201 models.

Check to see if the keyboard has power by hitting the
shift-lock key. The shift-lock light should go on.
If it does go on, try the setup key. If you get a setup
screen, then the keyboard is probably ok, and you
actually have a communication problem between the
terminal and the computer.

A common problem seems to be corrosion on the connectors
inside the keyboard. This is the connectors use to attach the
plastic circuit board to the main logic board. They are
tightly held, and you may need to un-bend the connector from
the circuit board. Putting it back together can also be
tricky, so do it as a last resort.

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