Gary C
Veteran Member
Does anyone have a spare BBC Master I/O controller CF 30050 ?
Need on to resurrect a sick master 128.
Thanks.
Need on to resurrect a sick master 128.
Thanks.
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CF30050
- Thread starter Gary C
- Start date
OceaneEmmerich
New Member
- Joined
- May 21, 2025
- Messages
- 1
If you can't find the right CF 30050, you can use a retro hardware clone such as GoSDC, Datacentre, or Compact Flash adapters for the BBC Master.
Gary C
Veteran Member
How would that work ?
The I/O chip does all the individual chip selects to things like the video processor, the via's etc so while the CPU is running, nothing is coming in or out.
The I/O chip does all the individual chip selects to things like the video processor, the via's etc so while the CPU is running, nothing is coming in or out.
jltursan
Veteran Member
Hard to find!. CJE is out of stock ,right?
Gary C
Veteran Member
Yep
Gary C
Veteran Member
Found one on stardot from a very nice person who had bought one but didn't need it and sold it at cost
Had found another fault in that IC21 had obviously removed from an (unsocketed) issue 1 board and there was a solder bridge between pin 11 and pin 10 meaning the CPU ready line was held high all the time but even with that sorted it didn't quite work.
New I/O IC fitted and greeted with 'this is not a language'
Result
Just need to add a battery and make up a speaker/rom slot piece in the printer and that's master number 2 up and running.
Had found another fault in that IC21 had obviously removed from an (unsocketed) issue 1 board and there was a solder bridge between pin 11 and pin 10 meaning the CPU ready line was held high all the time but even with that sorted it didn't quite work.
New I/O IC fitted and greeted with 'this is not a language'
Result
Just need to add a battery and make up a speaker/rom slot piece in the printer and that's master number 2 up and running.
Gary C
Veteran Member
So, with the new I/O controller, I have had more fun and games.
Found more issues around the board, bad contacts, more wrong spec logic IC's (74LS rather than 74F & 74S) but basically after a good clean, the soldering of a leg that had been missed and the cleaning off of the solder flashings the machine was working quite nicely.
Except, while it would boot to DOS plus, trying to start GEM would result in it locking up 99 times out of a 100. Thinking it was a memory issue (as at the point it locked, it was filling the screen with a white background) I investigated the ram and all the logic, but to no avail.
In a flash of inspiration, had a look at pin 7, processor is still running, check NMI, nope that's low. No wonder its not doing anything. Running a boot and monitoring NMI it is asserted many times, but only locks up when starting to draw the screen. Obviously its calling for a service but its not returning for some reason. NMI in a Master 512 with nothing else plugged in can only come from the IO controller, the same CF30050 that I had to replace above. Pulled it out, cleaned up the socket and IC and now it works I also tried the original CF30050 and it didn't work so that was genuinely faulty. Thing is with this machine, because the original owner had socketed everything, I have been chasing several faults at once.
Not sure if it was NMI being asserted badly (not sure how !) or it wasn't seeing something it was waiting for, but its now working fine Got a replacement genuine speaker/rom socket guide, a genuine two button Acorn mouse (that just needed a new IR transmitter) and its all working perfectly
Next !
Found more issues around the board, bad contacts, more wrong spec logic IC's (74LS rather than 74F & 74S) but basically after a good clean, the soldering of a leg that had been missed and the cleaning off of the solder flashings the machine was working quite nicely.
Except, while it would boot to DOS plus, trying to start GEM would result in it locking up 99 times out of a 100. Thinking it was a memory issue (as at the point it locked, it was filling the screen with a white background) I investigated the ram and all the logic, but to no avail.
In a flash of inspiration, had a look at pin 7, processor is still running, check NMI, nope that's low. No wonder its not doing anything. Running a boot and monitoring NMI it is asserted many times, but only locks up when starting to draw the screen. Obviously its calling for a service but its not returning for some reason. NMI in a Master 512 with nothing else plugged in can only come from the IO controller, the same CF30050 that I had to replace above. Pulled it out, cleaned up the socket and IC and now it works
I also tried the original CF30050 and it didn't work so that was genuinely faulty. Thing is with this machine, because the original owner had socketed everything, I have been chasing several faults at once.Not sure if it was NMI being asserted badly (not sure how !) or it wasn't seeing something it was waiting for, but its now working fine
Got a replacement genuine speaker/rom socket guide, a genuine two button Acorn mouse (that just needed a new IR transmitter) and its all working perfectly Next !