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dave wrote:

Jeff wrote:Does anyone know what the 'H' means in the H/D/M? prompt?
/Jeff

It stands for Hard disk.

As opposed to "D" for the floppy Disk?

Was there ever a hard disk option?

/Jeff

I replaced the two original power supplies with a new 5V 10A regulated power supply that I ordered from China. Screen Shot 2014-04-17 at 8.23.24 PM.JPG I also ordered two new 8T26's and installed them on the 541 board and powered up the computer. It would not boot. Removing them restored boot operat...

I sent you via email, my efforts to date to trace out the schematic of the 541 board. I am working from hires photos of the top and bottom of the board first so as not to damage the board itself. I sent the file via email as it was too large (36MB) to attach. I am still not finished. I am hoping, on...

WOW WOW WOW! Now I REALLY have to get this system up and running, although I have no Idea how/where I am going to get a System disk for it. Thank you for digging this info up. I found this sticker on the back of the unit, so perhaps it really is a Ma/COM Keymate C-100! Screen Shot 2014-04-16 at 5.24...

Does anyone know what the 'H' means in the H/D/M? prompt?
/Jeff

Hi All, An update. Well, I put it all back together (without those two 8T26's on the 541 Mystery Board), fired it up to start investigating the address bus when something miraculous happened when I shorted the reset pins. http://i1056.photobucket.com/albums/t361/chaosdesignsG5/ScreenShot2014-04-03at...

I thought I would post an update. I have spent a whole lot of time investigating the 8T26's and the data bus in general. I first started by removing all the 8T26's from all the boards, essentially isolating the data bus to the 505 board only. All data lines pulsed nicely on the 505 board and the con...

Please put my name down for one! Thanks

/Jeff

I tested the CPU. Lots of activity starts to happen on the address and data lines when I short the red and black wires causing a reset. There is a clock signal on 39 and 37, 34 and 3. I get data activity on DB lines except DB1 and DB5. I get activity on all address lines except AB4, AB5, AB6, AB7, a...

I have ordered a new 5V 10A regulated power supply from China. It will be here in 3 weeks to a month. In the meantime I have a spare 5V 3A that I am using in place of the old one that is outputting 11+V. My oscilloscope arrived and I have verified that Phase 2 is getting to pin 39 of the CPU. I have...