On 08/01/2017 07:31, "Tony Duell" <ard.p850...@gmail.com> wrote:
> On Sat, Jan 7, 2017 at 11:37 PM, Adrian Graham > <wit...@binarydinosaurs.co.uk> wrote: >> Evening all, >> >> I wish I had the ability to take a board layout and turn it into a logically >> laid out schematic but as yet I don't. Video sync on my Executel 3910 is >> still running me round in circles so could one of you fine folk take a look >> at this board layout drawn as best I can: >> >> http://www.binarydinosaurs.co.uk/STCExecutelSyncCircuit.jpg >> >> ...and let me know what it does please? The chip on the left is a Plessey > > > I don't believe it's correct as drawn. For one thing you have V333, an NPN > transistor, with the collector grounded (and no -ve supplies on the circuit. > For > another, R322 is ridiculously low. And I would expect the anodes of the > 3 diodes on the RGB outputs to go somewhere other than a resistor to > ground. Hm, ok, that's today's task then. For V333 it could be that I just have the pin numbers reversed but I'll double check. The diodes bothered me too and I'm trying to think of a better way of tracing unknown lines on the bottom of the board. My sponge-wrapped-in-tin-foil method isn't infallible. Cheers! -- Adrian/Witchy Binary Dinosaurs creator/curator Www.binarydinosaurs.co.uk - the UK's biggest private home computer collection?