Reviving VT220?

[Aaron Jackson]

Unfortunately I do not have an oscilloscope anymore. I've been trying to
find a cheap one on eBay for a few months but the prices seem very high
these days. I might be able to borrow one. For now I just have a true
RMS multimeter.

I've tried both extremes of the contrast and brightness but the screen
is completely off. This is the amber version of the 220 if that makes
any difference. I can't hear any high pitched whining from the flyback,
which I can hear from my 420. All the large caps seem to be giving a
very close reading considering I haven't taken them off the board.

This terminal was working fine until about two months ago. It was in a
air conditioned server room and probably hadn't been powered off for 5
years or so until we had a long power cut, after which it didn't
work. Does this provide any insight?

Thanks,

Aaron.


Tony Duell writes:

> On Sat, Apr 29, 2017 at 4:19 PM, Aaron Jackson <aaron at aaronsplace.co.uk> wrote:
>> Seems to be working fine as a terminal hooked up to the TV which is good
>> news. I am sure you are correct about me having made a measurement error
>> there...
>
> So the logic side is working. The problem is very likely to be in the
> monitor circuit,
> page 16 of the schematics.
>
> What test gear do you have? Do you have a 'scope, for example?
>
> Can you get anying on the screen if you adjust the brightness preset?
>
> -tony