Don't know if anyone can help me on this. I've discovered through trial and error that two of my comm cards for my 6800 (two MP-C) have issues.
The first MP-C has been modified to use a 6850 rather than 6821. I've had it working for long stretches but now and again it glitches out, as it is now, and I can't get anything from it at all. I know the computer is okay because if I hook up my MP-S, everything is okay. Sometimes fiddling with the baud selector switch eventually gets it back.
The second MP-C I have came with my second 6800 system. It has a 6821. It had a bunch of mods and an extra connector for something marked 'TI'. No idea what it did. To simplify, I removed it, restored traces and jumpers and set it up for 300baud. For the most part, it works. However I've noticed sometimes it won't work unless I leave the computer running for a good minute or so, like it needs to warm up. Then it produces data. For the most part, what it puts onscreen is correct, however now and again the CT1024 picks up random characters, mostly ? but sometimes others. It doesn't seem to affect operation much - if I go to load a tape, it'll sometimes put a whole bunch of ? onscreen or even show the S records as they're being read in (not sure if that's how it's supposed to work.. with my MP-S card it doesn't do that). Even if garbage characters come up during the load it still appears to load the data correctly.
Not quite sure where to start here.
The first MP-C has been modified to use a 6850 rather than 6821. I've had it working for long stretches but now and again it glitches out, as it is now, and I can't get anything from it at all. I know the computer is okay because if I hook up my MP-S, everything is okay. Sometimes fiddling with the baud selector switch eventually gets it back.
The second MP-C I have came with my second 6800 system. It has a 6821. It had a bunch of mods and an extra connector for something marked 'TI'. No idea what it did. To simplify, I removed it, restored traces and jumpers and set it up for 300baud. For the most part, it works. However I've noticed sometimes it won't work unless I leave the computer running for a good minute or so, like it needs to warm up. Then it produces data. For the most part, what it puts onscreen is correct, however now and again the CT1024 picks up random characters, mostly ? but sometimes others. It doesn't seem to affect operation much - if I go to load a tape, it'll sometimes put a whole bunch of ? onscreen or even show the S records as they're being read in (not sure if that's how it's supposed to work.. with my MP-S card it doesn't do that). Even if garbage characters come up during the load it still appears to load the data correctly.
Not quite sure where to start here.
