1980s_john
Experienced Member
Early last year I bought a pair of Horizons (came as one lot), there were fairly dusty but appear to complete. They are both mkII (metal rather than wooden case), twin full height floppy drives, and each with three S-100 cards - Z80 processor, 64K RAM, floppy disk controller (FDC). I've cleaned one of them up so far, using the usual simple techniques - remove the cards and drives, blow out all the dust, brush down with a small paint-brush to remove further dust, power up on a variac and check capacitors are OK and PSU voltages are good. Finally I cleaned up the socketed ICs (some of the pins had a very thin black oxide coating, easily removed), replaced the boards and powered it all on. The right hand floppy drive came on for 20s, but nothing was seen on the serial port, and when I tried (supplied) boot floppy made no difference.
Now the hard part comes - how to fix it? I found the following thread on comp.os.cpm which gives some great pointers:
http://www.digipedia.pl/usenet/thread/1833/28/
so I have plenty to try out.
I'd also like to test out the floppy drives, I found Tezza's post here:
http://classic-computers.org.nz/blog/2009-01-18-kaypro-drive-repair.htm
describing some techniques. Is there a PC DOS equivalent to Floppy Doctor please?
Also, can anyone help with some on-line Horizon manuals. I found some on bitsavers, but Dave Dunfields site (along with all the rest of classiccmp) seems to be down at the moment:
http://www.classiccmp.org/dunfield/s100/index.htm
I don't quite know what the motherboard does, other than provide serial and parallel ports. btw the Z80 processor card looks like you can solder in a socket and some other bits and pieces to allow a 2708 monitor EPROM to be added, I will try this as a last resort though. Maybe I might be tempted to buy a S100 EPROM board (eg http://n8vem-sbc.pbworks.com/w/page/4200908/FrontPage)
I've also yet to start work on the 2nd Horizon (slightly grubbier than the first), I've bought some spray paint for the metal cover - I always like to get things clean and scratch free first, somehow if it looks nice then I find it easier to work on - bizarre!
I also have an unmade kit of parts for a S100 bus probe (had the PCB for about 3 years now, maybe finally I have some incentive to build it - my last S-100 machine worked perfectly so no need for the bus probe then).
Anyway, plenty for me to go away and tinker with, hopefully someone here can give yet more great advice, as it is always welcome.
Regards,
John
Now the hard part comes - how to fix it? I found the following thread on comp.os.cpm which gives some great pointers:
http://www.digipedia.pl/usenet/thread/1833/28/
so I have plenty to try out.
I'd also like to test out the floppy drives, I found Tezza's post here:
http://classic-computers.org.nz/blog/2009-01-18-kaypro-drive-repair.htm
describing some techniques. Is there a PC DOS equivalent to Floppy Doctor please?
Also, can anyone help with some on-line Horizon manuals. I found some on bitsavers, but Dave Dunfields site (along with all the rest of classiccmp) seems to be down at the moment:
http://www.classiccmp.org/dunfield/s100/index.htm
I don't quite know what the motherboard does, other than provide serial and parallel ports. btw the Z80 processor card looks like you can solder in a socket and some other bits and pieces to allow a 2708 monitor EPROM to be added, I will try this as a last resort though. Maybe I might be tempted to buy a S100 EPROM board (eg http://n8vem-sbc.pbworks.com/w/page/4200908/FrontPage)
I've also yet to start work on the 2nd Horizon (slightly grubbier than the first), I've bought some spray paint for the metal cover - I always like to get things clean and scratch free first, somehow if it looks nice then I find it easier to work on - bizarre!
I also have an unmade kit of parts for a S100 bus probe (had the PCB for about 3 years now, maybe finally I have some incentive to build it - my last S-100 machine worked perfectly so no need for the bus probe then).
Anyway, plenty for me to go away and tinker with, hopefully someone here can give yet more great advice, as it is always welcome.
Regards,
John