View Full Version : Ampro Series 100/LittleBoard Bookshelf System Fixup/Restore

December 1st, 2017, 05:15 AM
link to Imgur album: https://imgur.com/a/jMnwK

I recently traded geneb for two Ampro Series 100 systems in exchange for building up a S-100 system with dual floppies and CP/M generated for it (still working on the S-100 system!). The Series 100 was Ampro's assembled system offering for the Z80-based LittleBoard, which is a single-board computer in a form factor that will bolt to the bottom of a floppy drive. Same idea as the Ferguson BigBoard, but 5.25" instead of 8", and using serial console instead of video. Neither system worked on arrival, which was fine since that was already known.

This is the restore of the first system, which was in worse shape of the two. It had dead RS-232 drivers, and a failed -12V inverter module. I ended up stealing the inverter module off of the other LittleBoard to confirm it was the issue on this one. They're apparently very common and cheaply available on eBay: I picked up 4 for $10 shipped, from a US seller. This particular board got restored first as it's the LittleBoard/PLUS which has SCSI! I haven't made use of the SCSI feature yet, but I plan on it. Here's a picture of the finished system up and running on floppies:

http://i.imgur.com/AsuWDmhh.jpg (https://imgur.com/AsuWDmh)

Someone had really beat on the case, it was rusty inside and had extra holes poorly drilled in the bracket that holds up the power supply and LittleBoard. I stripped the whole thing down, cleaned it, and painted the internal bracket and the black anodized part of the case. The info sticker was masked off before painting.

http://i.imgur.com/l14Jkxmh.jpg (https://imgur.com/l14Jkxm)

http://i.imgur.com/SALvrBZh.jpg (https://imgur.com/SALvrBZ)

Next problem was the power supply: I had repaired the LIttleBoard using a bench supply after noticing how crusty the original open frame switcher was:

http://i.imgur.com/tUFhnhDh.jpg (https://imgur.com/tUFhnhD)

Seems the caps are leaking, and at least one was physically knocked off the board (you could see where the leads had pulled out of the solder on the back side):

http://i.imgur.com/xcB9R6Xh.jpg (https://imgur.com/xcB9R6X)

Replaced it completely with a Mean-Well RD-50A from Mouser. It was less than $20:

http://i.imgur.com/ioii95Kh.jpg (https://imgur.com/ioii95K)

Fits perfectly, and there were already extra holes drilled in the bracket it mounted to, so I didn't feel bad about adding two more. It fits inside the PEM studs for the old supply module, so it's 100% reversible, should I ever find a replacement supply and/or want to switch back. The Mean-Well supply is also universal input, 100-240 VAC, 50-60 Hz, unlike the single-voltage original.

This isn't a full writeup, I just thought folks might be interested to see the progress on this! Seems to be a stable little system, I left it running for several hours, and was able to copy floppies from A: to B: and then boot them in A:. ZCPR directory listing of the boot disk, on the VT220:

http://i.imgur.com/8wTqYS5h.jpg (https://imgur.com/8wTqYS5)

December 2nd, 2017, 01:59 AM
Very nice! I've got an Ampro Little Board Plus system myself. It's presently built up in a boring PC chassis, but I use it a lot. I've got 88MB of a 2GB SCSI disk in use for CP/M on it. I use my DEC VT-102 as its terminal.


December 2nd, 2017, 06:18 AM
Hi Mark! I think it was your LittleBoard writeup that got me looking for one in the first place :) I also enjoy your 8085 projects, being a fan of the 8085 myself:


I'm thinking I will either end up using a SCA drive in an external enclosure (88 MB of probably 18.2 GB!) or a magneto-optical drive set to non-removable mode. The MO drive is particularly attractive since I can then just eject the cartridge and back it up on my desktop, and I'm pretty sure the little Z80 can't outpace the MO drive, even though it is slowish. Perhaps a good use for the few 128 MB drives/cartridges I've got.

December 2nd, 2017, 06:25 AM
So what are you going to use this system for? After all, they were intended for commercial/industrial applications.

December 2nd, 2017, 06:56 AM
So what are you going to use this system for? After all, they were intended for commercial/industrial applications.

Likely just as a compact CP/M machine. Especially with a hard disk, I can use it for assembling 8080/8085/Z80 stuff and transfer it to other systems over serial. The system disk also came with utilities for working with many other CP/M formats, so that's handy too.

Perhaps it will be sufficient motivation to get me to implement my own SCSI Flash disk :)

December 2nd, 2017, 03:18 PM
An excuse is needed to own and operate an Ampro??

December 4th, 2017, 12:04 PM
Excellent work! Thanks for posting the pics. I love how neat the new power supply installation is. (You could make it nicer by replacing the nylon wire ties with waxed lacing cord. :D )

It's nice to see the system back up and running.


December 15th, 2017, 04:45 PM
Brings back memories- used those in the early 1980s, used a custom board to interface with the flight computer of a P3 Orion. Ampro's implementation of the CP/m floppy disk drivers made use of dead data on the stack, which played hell with my interrupt handlers. Lots of ZSID and custom code to monitor memory to nail the problem. Called them up to confirm that was what they were doing- was not happy with them. Ended up writing a lot of code to get around them, like disable my interrupts when writing buffers to floppy, timing everything not to lose data. Switched to an 80186 Ampro when they first came out. Still use Ampro PC104 systems. They stopped using dead data on the stack.

December 22nd, 2017, 10:10 AM
Hah, good info! I could definitely see that wreaking havoc. I also use some of their industrial embedded stuff for day-job work. Still high quality.