VT101 screen adjustment

[Adrian Graham]

On 10/05/2016 16:10, "tony duell" <ard at p850ug1.demon.co.uk> wrote:

> [VT101 with vertical linearity problems]
> 
>> Yes indeed. Fortunately this one wielded under my trimmer and all is
>> properly aligned now. All I need to do now is troubleshoot the keyboard
>> circuit which I hope is the same as the VT102...
> 
> In general it is a bad idea to cure faults by adjustments. Unless somebody
> has been twiddling, these adjustments only drift if some other component is
> failing. They are there to initially set the circuit up for the components
> that
> are used, or in some cases, particularly in delta-gun colour CRTs, to correct
> for external conditions, such as magnetic fields.
> 
> My guess is a capacitor is failing. So far you are still within the range of
> the
> adjusment, but it may well get worse. I don't know which video board you
> have (there are at least 3 different ones), but if it's the one on pages 54-58
> of the VT100 printset on bitsavers (the VT100 and VT101 use the same
> video board), then check C318 and C319 for a start.

It's the same board as the VT102, just checked. I can easily check the caps.

Cheers,

-- 
Adrian/Witchy
Binary Dinosaurs creator/curator
Www.binarydinosaurs.co.uk - the UK's biggest private home computer
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