Great, my VT52 is shot.

[Bill Degnan]

On Fri, Apr 17, 2020 at 2:21 AM Brent Hilpert via cctalk <
cctalk at classiccmp.org> wrote:

>
> On 2020-Apr-15, at 5:23 PM, Chris Zach via cctalk wrote:
>
> > Wonderful: A few weeks ago I forgot to turn off my VT52 and left it
> running for a day or two. Now the screen is filled with snow and it looks
> like the text is all over the place horozontally.
> >
> > Any tips or thoughts on where to start looking to fix? The keyboard
> seems to be working as does the RS232 input (the snow on the screen changes
> when the pdp11 talks to it)
>
>
> Try turning the contrast or brightness up till the black level starts
> becoming illuminated. Is the raster (the screen character field / framing
> rectangle) stable?
>
> If no rectangle or stable display field becomes apparent then as Jon
> suggests it may be loss of sync, probably horizontal, and likely to be in
> the monitor circuitry.
>
> (Any affect from twiddling the H or V sync controls?)
>
> If the raster is stable then it might be something in the character
> generation pipeline (the character generator or the row pixel serializer),
> or in the monitor video amp.
>
> ("snow" as a description leaves for a range of possible interpretations.)
>
> There's always checking power supply levels to start with. In addition to
> the +5, there's probably a +/-12 or -5 for the character generator.
>

Ian Primas knows a lot about these.  (snark).....but def check the power
first, the large filter caps.  I have a working VT50, which is similar but
not exactly.  If you leave a terminal on for a long time and it dies,
that's a power issue or power related (caps resistor fried diode, etc.)
IMHO.