Acorn RISC PC - just lost video output - Page 1
Forum section: electronics / repair

author: angust_uk
author_rank: Regular Contributor
timestamp: May 08, 2018, 12:00:08 pm
content: Hi allI recently got my hands on a RISC PC 600 from eBay (having wanted one since I was 13!), and on doing some preliminary testing managed to get to a supervisor prompt, although the keyboard did not respond at all (tested with 2 different PS/2 keyboard). Following resets and restarts with various keys held down I've managed to make things worse as now both monitors I have (standard VGA models, reasonably recent) report an unsupported resolution.From my vague memory of Acorn video modes I do recall this being a problem with my old A3010, but anyone know of any way of forcing it to a 'standard' resolution? Of course this will probably involve the keyboard which doesn't work, so has anyone else experienced this as well? I've verified the PS/2 clock and data lines reach the I/O controller (and that the voltage rails and reset lines are as expected), but I'm not sure where to go next. Any help would be greatly appreciated!Thanks!Angus

author: anachrocomputer
author_rank: Regular Contributor
timestamp: May 08, 2018, 10:13:38 pm
content: You may need to reset the data in the CMOS memory, if the machine has been unused for some time and the batteries are dead. To do this, you will need a working keyboard! Press and hold the DEL key, and then switch the machine ON. Keep holding DEL until it has booted up:https://retrocomputing.stackexchange.com/questions/1540/why-does-my-acorn-riscpc-display-the-post-boot-errorHope that helps!Can you tell us a bit more about the trouble you're having with your PS/2 keyboards?

author: angust_uk
author_rank: Regular Contributor
timestamp: May 09, 2018, 08:45:09 am
content: Hi! Many thanks for the reply; I have already removed the battery and cleaned up the board in that area (I haven't yet checked whether any tracks are damaged, but they look to be ok). If the RTC/CMOS memory device is damaged (or there is an issue with the traces) do you think this may cause this symptom?To be honest I'm not sure where to go next with the keyboard issue; I've checked continuity to the IO controller IC (both PS/2 data and clock), and made sure the keyboard's supply is present (it is). I guess I could look at the data bus when pressing keys on the keyboard to see whether it getting that far, but I'm not sure how much help that would be!Thanks againAngus

author: bd139
author_rank: Super Contributor
timestamp: May 09, 2018, 09:09:10 am
content: You're lucky with the battery. I bought an RPC600 a couple of years ago and the battery had destroyed it. Had to scrap it. Was a monster 3 slice case so I made my investment up in ROMs and case parts eventually.Do you have a floppy drive? They flash the POST error codes on the floppy LED usually if there are any.

author: angust_uk
author_rank: Regular Contributor
timestamp: May 09, 2018, 10:14:38 am
content: Thanks for the tip re. fault codes; I'll check when I'm back home later (I'd disconnected the floppy whilst trying to figure out what's going on). I might be a bit premature in declaring the PCB fault-free; I did have to do a bit of cleaning originally, and as I mentioned, I've not yet delved into detailed continuity tests to make sure no tracks have been eaten!