Cromemco FDC

MikeS wrote: OK. Sorry for the delay, life has been very busy. I finally have a little hobby time, so I pulled out my Cromemco loaded IMSAI: http://wsudbrink.dyndns.org:8080/images/cromemco/outside.JPG and my SA851s: http://wsudbrink.dyndns.org:8080/images/cromemco/drives.JPG Cards front to back: http://wsudbrink.dyndns.org:8080/images/cromemco/inside.JPG ZPU CompuPro RAM17 (It plays nicer with the Dazzler than the 64KZ) Dazzler 1 and 2 16FDC D+7A Here is the 8 inch interface cable: http://wsudbrink.dyndns.org:8080/images/cromemco/cable.JPG http://wsudbrink.dyndns.org:8080/images/cromemco/cableclose.JPG Cable modifications (they are a little hard to see): FDC16 SA851 2 14 side select 4 32 drive select 4 18 30 drive select 3 24 18 motor on 10 NC seek complete (severed) 12 NC restore (severed) 14 NC eject 30 NC unused 32 NC unused NC 2 reduced write current (TG43) NC 4 unused NC 10 unused (severed) NC 12 disk change (severed) NC 24 sector So, what about TG43, reduced write current? On the dual 851s, I had "plug IW (write current switch)" removed. This has worked fine up until now. On my "Dunfield memorial ImageDisk box": http://wsudbrink.dyndns.org:8080/images/cromemco/imgdsk1.JPG http://wsudbrink.dyndns.org:8080/images/cromemco/imgdsk2.JPG I use the ImageDisk parallel port TG43 driver and "plug IW" is jumpered to "interface" on the single 851 it uses. So, I've given this some thought and decided to implement TG43 on the 16FDC. My bench is currently full of SWTPC: http://wsudbrink.dyndns.org:8080/images/cromemco/bench.JPG http://wsudbrink.dyndns.org:8080/images/cromemco/bench2.JPG but I figured I could do this "around the edges" and in my lap. Here is the card before any mods: http://wsudbrink.dyndns.org:8080/images/cromemco/16fdcfront.JPG http://wsudbrink.dyndns.org:8080/images/cromemco/16fdcback.JPG Here is a close up of the "PHANTOM" mod we discussed a while ago: http://wsudbrink.dyndns.org:8080/images/cromemco/phantom.JPG A quick look through the schematics suggested reusing the eject driver on IC40 (8T98). I took a 16 pin socket: http://wsudbrink.dyndns.org:8080/images/cromemco/socket.JPG bent out pin 14 and soldered a 2 inch piece of 30 gauge wire to it: http://wsudbrink.dyndns.org:8080/images/cromemco/socketwire.JPG I soldered the other end of the wire to pin 29 of IC26 (the 1793). I removed IC40 from its socket on the board, inserted it in the socket and inserted the socket into the board: http://wsudbrink.dyndns.org:8080/images/cromemco/patch1.JPG http://wsudbrink.dyndns.org:8080/images/cromemco/patch2.JPG Finally, I patched FDC16 pin 14 to SA851 pin 2 on the interface cable: http://wsudbrink.dyndns.org:8080/images/cromemco/cabletg43.JPG and rejumpered IW to interface on the dual 851s. No cuts on the 16FDC and everything works. The only "downside" is a wire soldered to a pin on the 1793. That can be reversed with a tap of the old soldering iron. I hope this helps, Bill Sudbrink