Inspection of the first chassis showed no obvious issues so i removed all the cards, disconnected the drives, and bravely powered up it up. The voltages looked sensible. There was no smoke.
I then put the cards back in and fired it up. Surprisingly, it came up ready for a boot disk. I tried my disks for the VT1303. Curiously the VT1303 word processor boot disk was labelled as also being for the RDS 201/202 and sure enough it worked.
The CP/M disk did not work. It booted but then reported that it was not for this system and then halted.
I found another image “Lexitron Raytheon VT Series CPM-85 Disks 1 & 2” Disk 2 that sometimes worked (I thought there were drive issues) and then I found CP-M 2.20D worked better.
The cataract issues were remediated in much the same way as the VT 1303.
I then started trying the cards from the second machine in the first. The processor cards appear identical, but CPM again reported that the system was incorrect.
- RAM Card is good
- Printer card is good
- The first FDD is good
- The second FDD does not read disks properly
After testing the disk cards, I had some problems getting the machine to start. This seems to have been the keyboard connectors. I gave them a clean (at both ends of the cable) and they came good. Symptoms included a continual beep or incorrect characters typed after boot, or random rubbish on the screen.
The system will give a start chirp if the printer card is missing, but will not start the boot process. The same if the second floppy disk controller is missing.
I repeated the exercise on the second chassis. The 5V line was 5.75V. It’s a switching supply. I found the voltage could be adjusted at the pot next to R75 – top right. Fully loaded it drops about 0.25V so I tweaked it up a little.
After cleaning a lot of edge connectors, this system also came up. Remarkable really. As noted earlier, the processor card does not work with the same version of CP/M as the other machine. I swapped the ROMs and it came good.
These are 2708 ROMs which are a problem for me. I don’t have a programmer that can read or write them (it on the “to be acquired” list). I adapted my EPROM programmer. I can now read 2708s through an adapter. I used a 2716 in the processor card with a hand made adapter.
The bottom line is that the two sets of cards are good except for one floppy disk controller.