Recent content by Amardeep-AC9MF

Well, I didn't get that far since the high voltage wasn't working I just put it away until I figure out what to do next. I'll try the HOT as a longshot but if that doesn't work I'll just ditch the CRT. Troubleshooting the mainboard should be okay since it's all discrete logic and I even have...

Did some further work on the machine. The power supply had some cracking Rifa line filters so I replaced those. Nice steady output on all the rails. The CRT filament glows but there is no high voltage. The flyback transformer was hanging off the board. It looks like one of the two mounting...

By the way, the original CP/M was FM disks and used the worst-case data pattern of hex E5 for the blank sector data, and thusly the "erased" directory entry value. Later when machines started using double density, CP/M still had to use E5 even though it was no longer the worst case data...

Actually I think that board is the only static RAM board I've seen that will work (it is new to me). It fully implements the bank assignment for all eight positions including the ability to always map the high bank for all boards in the system when bit 7 is selected.

Are you certain 64KZ are not supported by Z80 Cromix? Mine seem to work fine. Back in the day my 11.27 system ran on a set of CCS 2066 boards. I have only ever owned one 64KZ-II which was that awful early revision B board that got bounced around between several people and the seller last...

For Z80 Cromix (versions up to 11.27) you need a Z80 CPU, a 16FDC with modifications to support the Shugart drives, and a minimum of two 64KZ RAM cards. A TUART would be needed to support additional concurrent user logins as well as the required additional RAM banks. There are no static RAM...

If you find the 8048 is bad, we can work out a mutually beneficial arrangement. Lend me the keyboard for a couple of weeks. I will program a replacement 8748, run some scans of the communication between it and the terminal, then return it to you with a new controller installed. I originally...

I understand the service manual gives some data on the various custom logic parts, perhaps enough to reproduce it. Have you checked there?

That was my fallback plan if unable to find a sample to examine. The main controller code is 8KB of 6800 so also manageable if all else fails. It's supposed to be a bidirectional one-wire protocol so it might be necessary to see both sides. Maybe not. I'll be poking through that. Thanks for...

I just received a QVT-102 from the Pacific NW via eBay. No keyboard. I'd like to reverse engineer the interface so we can build an adapter to us a PS/2 or USB keyboard. But neither of the Qume manuals for this terminal document the protocol. If anyone would be willing to lend me their...

It's surprising how little documentation still exists for a system that was so popular in the day. I think when people moved on to the PeeCee world they binned much of it. Thankfully enough still exists to keep going. I have an 820-II for which I'm going to recreate the floppy disk controller...

Nice work, fellas! I suspect it was a marketing requirement to make it upper case only. Very likely they didn't want to hurt the sales of some other product(s) in the catalog. Possibly printers.

Wow, that's great progress! I have no doubt that adding the character bitmaps to the table along with the minor code changes to eliminate the translation to upper case will produce the desired results. This will be one of those milestone moments in retrocomputing history where something...

Being experienced in MCS-48 for many years, I had some plans to look into disassembling the ROM to see if lower case can be implemented. Technically there should be no problem but who knows how gnarly the code is. But I have a long backlog of things to work on so it will take me a long while...

Testing is key. Too many things in the retro community have to be sourced from places where you can't count on the authenticity of the product. BTW, thanks for all the awesome designs you've shared over the years. I purchased one of your ETA-3400 boards a while back and look forward to...