On Sat, Jan 21, 2017 at 4:27 PM, Adrian Graham <wit...@binarydinosaurs.co.uk> wrote: > Back to the Executel after a few days relaxing :) > > On 17/01/2017 20:59, "Tony Duell" <ard.p850...@gmail.com> wrote: > >>> Yep, on the left two. I haven't dared to pull them from the board though >>> even though they're socketed. >> >> Do be careful, the substrate is a brittle ceramic material... > > I don't think I'll touch them, they're obviously part of the phone subsystem > and I doubt I'll ever plug it into a phone line - I have several One Per > Desks for that sort of thing if needs be.
A telephone line similator is a useful toy to have for something like this. I have an old but good one (it use a TMS320 series DSP for signal degredation) that I bought non working on Ebay. Reseating the socketed chips helped, replacing a couple of comparators and a voltage regulator fixed it -- the problem of course being to find the faulty parts (there are well over 300 ICs in the unit). [...] >>> I have, a small 16 channel one that's Saleae Logic compatible so I'm slowly >>> learning how to drive that too. I should be able to decode addresses and >>> suchlike using it shouldn't I. >> >> Can you clock the analyser from an external input rather than sampling >> every 10us or whatever? If so, clock it from the Rd/ signal and grab the >> 16 address lines (8 on the processor pins, 8 on an address latch, most >> likely a 74LS373, which you will have to find!). Now you can see the >> sequence of locations that the CPU is reading. Most (but not all) will be >> instructions. Find one, compare with the listing, see if the sequence makes >> sense. > > I can trigger it on the RD signal yes. There's 2 LS373s which both had dead Not trigger, but clock. In other words to take a sample on every Rd pulse. -tony