Hi fellow Cromemco fans.
I have just joined the group - so I thought I would say a brief hello.
I live in the UK (Worcester to be accurate) and own 'bits' of a Cromemco Z-2D.
I have 3 sets of Cromemco S-100 cards that I obtained a few years ago from a guy who had thrown the 3 chassis away but kept the cards (weep). Mainly 16FDC, 64KZ and ZPUs. I have a number of TUART cards, PRI cards and a glut of D+7A cards. The odd 64FDC thrown in there for good measure...
The Z-2D chassis, power supply and Blitz Bus was obtained from Marcus a good few years ago also. I had a couple of faults with the bridge rectifiers on the power supply (all fixed now) but was having problems successfully bringing the system up. I have recently been helping someone over on VCFED with their system - so that has rekindled my interest in the Cromemco, and I have started to work on it again.
I see a few names on here I recognise from VCFED!
I had a basic system of a 16FDC, 64KZ and ZPU. On power-up I see a brief flash of activity on the 16FDC transmit line and then nothing. I have replaced the 3 boards with another set - and observed exactly the same issue. I have also tried with an RPi and minicom connected via a USB/RS232 converter. Nothing.
I have an RS232 line monitor on the 16FDC console, and the transmit line is not actually active when powered up (apart from the initial activity). It is almost as though the 16FDC is sending out a continuous <BREAK>.
As there is no hard RESET on the TMS5501 UART, I am beginning to suspect that the ZPU is not running properly to initialise things. However, that could point to any of the 3 cards I have in the system.
I have written some test firmware to replace RDOS on the FDC that doesn't require a RAM card to operate - but (unfortunately) I don't have the immediate means to burn a 2708 EPROM available. I will see if a friend of mine has an EPROM programmer that I can use.
The DC power rails look OK - so I am beginning to suspect the Blitz Bus backplane. I shall remove it and see if there is any damage to it anywhere obvious. One of the S-100 connectors did have a bit of corrosion on it - but I did try to rescue it. Perhaps I only think I did a decent job and some of the S-100 lines are cross-coupled in someway?
If that doesn't give any joy - I might have to break out the oscilloscope and logic analyser...