On 04/02/2017 02:36, "Jon Elson" <el...@pico-systems.com> wrote:
>> http://www.binarydinosaurs.co.uk/STCExecutelA1checking2.jpg >> >> Pulse missing from ROM3. > First pic, pulses are missing from ROMs 1-3, seen on ROM4. > But, those pulses on ROM4 are really narrow, and may be > noise, or very narrow glitches. Any time you see really > narrow glitches, especially when they are one LA sample > wide, you have no idea what they actually look like. The LA Gotcha, I forget that any circuit can be a haven of noise and like you say the LA is just detecting that there's something there at that point in time. The fact that the logic software even has a 'glitch filter' on each channel should've given me a clue. > the circuits responding to such glitches. I think you are > chasing your tail about these things, and missing a real > malfunction that is not related to this. Could be EPROM > bits that have faded, one shot capacitors that have changed > value or something. I've tested all the caps apart from the .47uF decoupling ones and replaced the dead or out-of-spec ones. This week I replaced all the ROMs with 'new' 2764s and changed the old sockets, I discovered that two of the original ROMs had gone open circuit. Fortunately I'd dumped them beforehand. I'll keep chipping away :) -- Adrian/Witchy Binary Dinosaurs creator/curator Www.binarydinosaurs.co.uk - the UK's biggest private home computer collection?
