Reviving VT220?

Aaron Jackson aaron at
Sat Apr 29 13:36:31 CDT 2017

> Since it doesn't smoke, I'm thinking the horizontal sweep
> transistor may have gone out.  It may have shorted, which
> then may have burned up the primary winding in the flyback
> (if left on long enough).  I'd check that transistor for a
> short, and then you can trace a few traces to identify the
> primary terminals on the flyback and see if they are an open
> circuit.

Hmm, not good news. zero ohm between pin one and three of the transistor
you mentioned. To be fair the board around it looks a little brown, but
I assumed this was just because it would have got hot. Could replacing
this cause damage to the flyback? I seem to have a low resistance on
what I think is the primary coil.

I am wondering if there was also a power surge when we had the power
failure that killed the terminal. If so, perhaps this is the only reason
why the transistor may have died.



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