VT100 preventative maintenance?

Jarratt RMA robert.jarratt at ntlworld.com
Sat Aug 22 13:43:48 CDT 2015

Oooh, didn't know about the diodes. Are there any specific ones that you
think should be replaced no matter what? If not, are there any tests you
would recommend?



On 22 August 2015 at 19:10, tony duell <ard at p850ug1.demon.co.uk> wrote:

> >
> > Should I leave well enough alone, or is there preventative maintenance
> that
> > should be done? For instance, should capacitors be proactively replaced.
> In
> > general, I'm thinking about things that, if they fail catastrophically,
> > would cause collateral damage.
> The main part you want to protect is the flyback transformer. It is very
> hard to
> get a good replacement now. Flybacks can just fail, but failure can be
> caused
> by defective diodes and capactors on the video PCB. Look at the schematics
> for
> your video board (there are at least 3 versions) for half-wave rectifier
> circuits that
> produce the CRT and video stage supply voltages from the flyback. You
> might want
> to check or replace those diodes and caps.
> A VT100 and models derived from it (VT105, etc) has an SMPSU. Defective
> capacitors
> on that can kill the chopper transistor, but that is in not impossible to
> replace.
> -tony

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