I posted a few months ago about a slightly unreliable BBC I was trying to bring back from the dead.
https://www.stardot.org.uk/forums/viewt ... p?p=447706
Needless to say, life got in the way, and I've only now come back to it to try to get it to work reliably.
It does work, switches on, good display, run various bits of test software and all appears well.
It has an MMFS ROM and SD Card reader installed, can play games etc.
There are two main issues, which may be related.
The first is that when I press down on the bottom right side of the motherboard the screen displays some spurious characters and the machine sometimes hangs. "Don't press on the motherboard" I hear you cry, and fair enough, but I am being a bit of a perfectionist and want the machine to work reliably. I'm guessing that there is an issue somewhere where either a broken or unreliable trace somewhere on the PCB, or a loose connection with an IC socket.
Other than that I had assumed the machine was working fine, had run various soak tests and it seemed to be ok. But, when playing certain games (Qwak! and Space Pilot are the two I've tested) weird artefacts appear on the screen.
With Space Pilot, random white pixels appear on screen as I move the ship around the screen and the game occasionally resets, moves to the next level of its own will or otherwise behaves oddly.
For those who don't know Qwak!, it's a platformer with tile based graphics, variosu tiles being laid out to make each level.
https://www.bbcmicro.co.uk/game.php?id=789
With this game, it sometimes confuses the tiles, replacing a block of stone with something else, or placing tiles in the wrong location on screen.
It's very baffling and I can't get to the bottom of what the issue is. I'd assume the issues with the graphics are caused by a problem with the RAM in some way? Could it be that a dodgy trace or connection is causing both problems? I've run a basic RAM test from the Watford Electronics diagnostic disk, but am I right in thinking this isn't very comprehensive?
Any suggestions for how to hunt down the fault would be greatly appreciated!
https://www.stardot.org.uk/forums/viewt ... p?p=447706
Needless to say, life got in the way, and I've only now come back to it to try to get it to work reliably.
It does work, switches on, good display, run various bits of test software and all appears well.
It has an MMFS ROM and SD Card reader installed, can play games etc.
There are two main issues, which may be related.
The first is that when I press down on the bottom right side of the motherboard the screen displays some spurious characters and the machine sometimes hangs. "Don't press on the motherboard" I hear you cry, and fair enough, but I am being a bit of a perfectionist and want the machine to work reliably. I'm guessing that there is an issue somewhere where either a broken or unreliable trace somewhere on the PCB, or a loose connection with an IC socket.
Other than that I had assumed the machine was working fine, had run various soak tests and it seemed to be ok. But, when playing certain games (Qwak! and Space Pilot are the two I've tested) weird artefacts appear on the screen.
With Space Pilot, random white pixels appear on screen as I move the ship around the screen and the game occasionally resets, moves to the next level of its own will or otherwise behaves oddly.
For those who don't know Qwak!, it's a platformer with tile based graphics, variosu tiles being laid out to make each level.
https://www.bbcmicro.co.uk/game.php?id=789
With this game, it sometimes confuses the tiles, replacing a block of stone with something else, or placing tiles in the wrong location on screen.
It's very baffling and I can't get to the bottom of what the issue is. I'd assume the issues with the graphics are caused by a problem with the RAM in some way? Could it be that a dodgy trace or connection is causing both problems? I've run a basic RAM test from the Watford Electronics diagnostic disk, but am I right in thinking this isn't very comprehensive?
Any suggestions for how to hunt down the fault would be greatly appreciated!
Statistics: Posted by studio_lowfi — Sat Jul 05, 2025 10:55 pm