11 Aug
2021
11 Aug
'21
9:41 a.m.
Tom,
On Wed, Aug 11, 2021 at 11:05:59AM -0500, Tom Uban wrote:
What do you use to connect an 8" drive to a
PC?
This adapter is useful: http://www.dbit.com/fdadap.html
But, if your floppy doesn't require a TG43 signal, you could just
wire a custom cable with no logic needed, or get something like this
on e-bay: https://www.ebay.com/itm/114924378003
Additionally, some PC floppy controllers do not work for some kinds
of floppy encodings. Here is the article I used as a guide. I've been
using an Adaptec AHA-1522A SCSI+Floppy interace, which has a good
FDC chip for optimum floppy format support.
https://retrocmp.de/fdd/general/disk-imaging.pdf
I'm all for not fixing it if it's not broken. But, I do suggest careful
inspection of the electrolytics on the motherboard and monitor, especially
since the monitor board is right above the logic board, so if a cap
phsically leaked, the corrosive stuff that comes out could drip onto the
logic board. I see this mostly in SMD style electrolytics, but have seen
those like the ones in my 820-II physically leak, and the damage can be
serious.
--
Mark G. Thomas <Mark at Misty.com>, KC3DRE
Ok, I was going by the appearance of my case being the
older style. I had not considered the number
of PROMs, but now that you mention it, my old Ferguson Big Board (which was an 820 clone)
only had
two PROMs.
If you still have any 8" floppies from your Big Board, these will probably
boot and work in the 820 as well as 820-II.
...
At some point, I need to ask someone to make me
bootable 8" floppies, but I suppose I need to
determine if it is 820 or 820-II first...
I can able to help you with floppies.
The floppies are standard
IBM 3740 Single Density and easy to write with Imagedisk software
and a PC-connected 8" drive. Both the
swithing supply in my 820-II and it's external 8" drive box
had failed. I replaced the supply in the 820-II case with a modern
switching supply that easily fit. The HV bleeder resister for my CRT
was arcing, so I replaced that. I replaced all the electrolytics on
the monitor board. I also replaced the sockets for my ROMs, as some
of their contacts "sprung" when I replaced the chips, but I do not
recommend doing this unless it is absolutely necessary and you have
good tools and practice.
I had not turned on my box for a number of years, but
when you posted, I decided to try it and it
worked perfectly, which I suppose is just lucky. I do have the tools and skills to work
on it if it
were to fail, but won't likely make changes unless it does. The 820-II
restoration was a fun and rewarding project. It is well
documented, easy to work on. It was also my first ever CP/M computer.
When I was in high school, the 820 motherboards were readily available
for $75.
Mark
It sounds like you had a good time, which in my opinion is the main goal!
--tom