DEC VT 320 with Terminal Disease - help?

From: Mark Tapley <mtapley_at_swri.edu>
Date: Fri Feb 21 15:44:01 2003

>Look at the flyback transformer. That is the ceramic thing with the thick
>wire attaching to the CRT tube. Does it have a crack around it with
>hardened "ooze" coming out of it?

Will look when I get home. I don't remember there being a wire that went
from the PS board to the tube, other than ground straps from the cage
assembly. There is a ceramic transformer-looking thing and the wires on it
are rusty, which is one of my second-order questions (how to get rid of the
rust and arrest the corrosion process).

>90% of the time the vt320's fail, it is this transformer shorting out, which
>takes the horozontal transistor(?) with it. It heats up, cracking open, and
>spewing out it's magic ooze. If this is the case, you can replace both of
>these parts, and it will work again. DEC used some really crappy flyback
>transformers in these things.

Is that transistor on the PS board as well? If so, why does the PS board
appear to work "unloaded"?
If that's the fault, are the scorch marks under the blue resistors normally
there, or unrelated?

>However, it would probably be cheaper just to replace the whole terminal
>in that case. The transformer will probably cost at least $30.00, and the
>transistor around $5.00. Then comes the fun part of trying to extract
>and replace them without destroying the circuit board.

Sigh. I may look on it as a learning experience, if I can find a
replacement transformer that fits.
                                                         - Mark
Received on Fri Feb 21 2003 - 15:44:01 GMT