Charles wrote: I'm glad to hear you got to the end of the chain of faults on your ADM-3A. I am still struggling with my ADM-5. The smoke I mentioned last time came got back to the monitor showing a cursor. I tried sending and receiving data and found neither operation worked. While I was looking into this problem(s), without any provocation the monitor went off, with the picture collapsing to a vertical line and fading out with no nasty noises or any other signs of distress. From previous experience, I checked the HDRIVE signal to the monitor and found it was absent. (The usual beep at power on did not happen after this either). Luckily, the ciruitry in this area seems to be identical to the ADM-3A so I can use the ADM-3A maintenance manual to troubleshoot it, however the component references are all different so it can still get very tedious. (I also found some frequencies listed on the timing diagram don't seem to be correct which doesn't help matters either). I eventually found a 74LS161 which is used to divide the master clock signal was not behaving correctly. Not having a replacement, I "borrowed" one that seemed to be working correctly from my other ADM-5 which has even more issues. This made the waveforms around the dot counter and character position counters look much more reasonable, however, I still don't have the HDRIVE signal restored yet so there must be another problem lurking and when I get to the bottom of that one, I will probably still have the data transmission and reception issues... While working on these latest issues, I remembered that the faults that led me to replacing the two 74LS125 chips on a previous occasion were certain received characters being incorrectly displayed due to stuck bits. I also noticed that I had to replace a 7805 voltage regulator during that troubleshooting session. I'm making lots of notes this time around so I won't have these recall difficulties next time around. This ADM-5 was stored in an attic space with poor temperature control for many years but since then and before the most recently failures, it had been in a less variable environment. The 74LS161 that failed was clearly working initially when the terminal came out of storage this time. It didn't seem to be a lead bonding issue either - the MSB of the count output seemed to be following the clock input. Every time I try to use my ADM-5 terminals, I seem to run into these kind of successive failures. I have some BBC Micro equipment from the same era which also contains a fair amount of TTL but it doesn't give anything like the same degree of trouble, although I did have to replace a single 74LS163 counter/latch in my oldest BBC micro. It was wired to be a latch only but it decided it's true destiny was to be a counter. This failure could have been a lead bonding issue. Regards, Peter Coghlan.