On 10/05/2016 16:10, "tony duell" <a...@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 collection?