10 May
2016
10 May
'16
12:12 p.m.
On 10/05/2016 16:10, "tony duell" <ard at p850ug1.demon.co.uk> wrote:
[VT101 with vertical linearity problems]
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
collection?
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.