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Repairing a VT220

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gardner:
I have a project that involves a DEC VT220.  I have clean looking 1983 late 1986 one with an amber tube.  The tube lights up and I get a "keyboard error 4" diagnostic and the LEDs on the keyboard all remain lit.  I have the EK-VT220-TM-001_VT220_Technical_Manual_Nov84.pdf and what looks to be at least a partial schematic that I downloaded from somewhere.

So far I have confirmed the keyboard cable is alright and the voltages inside the keyboard check out.  I'll next sniff the comm lines to the keyboard and see if the two units are talking.

I'm curious if anyone's done work on a VT220 and has pointers what is most likely to be failing.  This one was last known working in about 1999 and could have physical damage internally, but most likely some of the elcos are failed.

EDIT: my unit turns out to be a later one, made in December 1986.

fourtytwo42:
If it's working well enough to display an error code there isn't much wrong with it so I should hitch up it's serial port to something and see if its able to receive and transmit. I imagine the manual you have would have a list of error codes anyway!

Gyro:
Damn, last time I used a VT220 it looked so modern, what happened!  :(

Yes I know, I got old.

Keyboard error 4 does ring a very faint bell though.  :-\  It's a keyboard micro reset error - something to do with dip switches on the underside of the keyboard maybe??? (It's a very faint memory, maybe nothing at all)

pfrcom:
Faint bell for me too - could it be a key stuck on the keyboard, or something holding a key down, while the terminal is powering on ?

IanB:

--- Quote from: Gyro on October 07, 2017, 05:59:06 pm ---Damn, last time I used a VT220 it looked so modern, what happened!  :(

Yes I know, I got old.
--- End quote ---

The 320 and later models did get slimmer and sleeker.

But if you think that looks clunky, imagine what the VT100 looked like!

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