PET mono screens

tony duell ard at
Tue Oct 27 08:33:20 CDT 2015

> ROM problems aside does anyone know of a way I can test the actual CRT?

By 'CRT' I assume you mean the evacuated glass thing. The term is alas also
misused to mean 'monitor'


> Back when I was fixing my broken TRS80s I could use the CRT from a B&W TV,
> is there anything oddball about the PET CRT that would stop me going the
> other way and putting the tube in one of my spare TVs?

There's nothing odd AFAIK about the Pet CRT. I am pretty sure it's one of the common
ones with a modified B7G base (7 pins) and a 12V-ish heater.

Before you go to all that trouble, why do you think it has failed? In all my time of working
on classic computers I've had exactly one mono CRT fail (and no colour ones). Fail meaning
'gives nothing on the screen' -- I've had a few with phosphor burn, or with low emission. But
those gave an image, albeit a dim one.

It is generally a lot quicker to see if the CRT is getting sensible voltages (and if it is, and you
still get nothing to then suspect the CRT) than to swap it out. Also make sure the heater is 
glowing (you can generally see the glow from the back end of the electron gun either through
the side of the tube neck, or in the pinch-off tube in the middle of the socket connector)



Owner of Binary Dinosaurs, the UK's biggest home computer collection?

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