Micro 80 Expansion - help with identification.

[shyandrewt]

Hi all. I bought this at a local clearance auction and was wondering whether anyone can help me identify it. The unit has dual 5.25in floppy drives installed and what I assume is possibly a parallel printer interface. Opening it up I see someone has put a "TRS 80"sticker and the PCB is marked ""MICRO 80 EXPANSION REV 12". The ICs on the PCB have date ranges from 82 - 84. I cannot find any images on the internet that look like this unit. I have previously picked up a TRS-80 Model I, Level II and a MT-32 memory/printer module at the same place and it is possible they are from the same previous owner.

I'm still a noob wrt TRS-80 and like computers so any insight is welcome. Thanks.

 

[Kool65]

Looks like a third party TRS-80 "Expansion Interface". The 40 pin cable at the front should connect to your model 1. Then you've got a disk controller via FD1771 IC, obviously 2 floppy drives, serial port via 1013 chip and 32K RAM expansion via 4x6264 Chips. I'd say a nice find

 

[bill.gunshannon]

And a Centronics printer port..

 

[Eudimorphodon]

I initially wondered if it might be a Micromint DISK-80:

The Micromint Disk-80 Expansion Interface

The Disk-80 was an alternative to the Radio Shack Expansion Interface that was sold by Micromint Inc. It was designed by Steve Ciarcia and was featured in his …

www.trs-80.org

in a custom box, but no, that looks like a manufactured item, and its use of static RAM is completely different. Where did you find it? (Country?) It’s very “modern” for a TRS-80 expansion, with the low profile drives.

 

[Eudimorphodon]

... FWIW, the AY-5-1013 chip is a UART, so it’s also an RS-232 interface, apparently. Missing the cable?

 

[shyandrewt]

I initially wondered if it might be a Micromint DISK-80:

The Micromint Disk-80 Expansion Interface

The Disk-80 was an alternative to the Radio Shack Expansion Interface that was sold by Micromint Inc. It was designed by Steve Ciarcia and was featured in his …

www.trs-80.org

in a custom box, but no, that looks like a manufactured item, and its use of static RAM is completely different. Where did you find it? (Country?) It’s very “modern” for a TRS-80 expansion, with the low profile drives.

Found in Melbourne, Australia. It does have a serial number sticker (just falling off the back) that is similar, but not identical to the S/N on the main PCB (check the attached pics). This gives the impression that it might be commercially assembled rather than a home-build - perhaps.

I'm looking forward to having a play in the future - and happy that it has a serial port interface also. I have pulled the cover off the power supply (mostly to check for RIFA caps, and check the voltages are all ok (+-12, +-5V) - pic of the label attached.

Thanks for everyone's suggestions so far.

 

[Kool65]

Found in Melbourne, now I know where to look
See attached advertisement from Micro-80 Magazine Vol 4, Issue 8, 1984

 

[shyandrewt]

Found in Melbourne, now I know where to look
See attached advertisement from Micro-80 Magazine Vol 4, Issue 8, 1984


View attachment 1266651

That's a great find - many thanks @Kool65 - Looks like my unit may be specced at the upper end of the options listed there - with two double-sided, double-density drives (Shugart SA455-3AA). Quite an investment in the day.

 

[Eudimorphodon]

with two double-sided, double-density drives (Shugart SA455-3AA)

Just to be clear, your drives are double density, but it looks like the controller IC on the board is a plain old WD1771 single-density chip. Presumably they intended to offer a piggyback “doubler” board for it at some point. (That’s why the drive capacity for the double sided 40 track drives are listed as 200k, not 360k.) It’s possible a doubler for a Tandy expansion interface would work, depending on if this uses the 1771’s internal data separator or not?

Anyway, it’s still a really nice piece of equipment. Was guessing it was probably Australian or another market where the Model I was sold a little later than the US.

 

[Gazza]

Tis your lucky day M8, way back in time a work M8 bought a System/80 complete with a Micro-80 Expansion and manual. The good news is I scanned the manual, the bad news is the files on the hard drive are corrupted, the good news is I found a backup. I just need to to combine the 40+ files into a single PDF.
If I remember correctly we had problems with the static rams in the EX and fitted 4164s in the keyboard - problem fixed.
I thought I sent Tezza a copy but I may be wrong. If your reading this Tezza let me know and I'll send you a copy.
BTW his Sys80 was the second of only 2 Romdos/80 computers - oh the memories

 

[shyandrewt]

Just to be clear, your drives are double density, but it looks like the controller IC on the board is a plain old WD1771 single-density chip. Presumably they intended to offer a piggyback “doubler” board for it at some point. (That’s why the drive capacity for the double sided 40 track drives are listed as 200k, not 360k.) It’s possible a doubler for a Tandy expansion interface would work, depending on if this uses the 1771’s internal data separator or not?

Anyway, it’s still a really nice piece of equipment. Was guessing it was probably Australian or another market where the Model I was sold a little later than the US.

Good point @Eudimorphodon - I would have missed that and got myself very confused...

Tis your lucky day M8, way back in time a work M8 bought a System/80 complete with a Micro-80 Expansion and manual. The good news is I scanned the manual, the bad news is the files on the hard drive are corrupted, the good news is I found a backup. I just need to to combine the 40+ files into a single PDF.
If I remember correctly we had problems with the static rams in the EX and fitted 4164s in the keyboard - problem fixed.
I thought I sent Tezza a copy but I may be wrong. If your reading this Tezza let me know and I'll send you a copy.
BTW his Sys80 was the second of only 2 Romdos/80 computers - oh the memories

Thanks @Gazza I'd be happy to do the recombination if you'd like. it's the least I could do!

 

[Gazza]

G'day @shyandrewt, managed to get all the files into a single PDF, hoping this helps.
For a double density board try
Ian Mavric ianm@trs-80.com

I managed to find the original owner on faceache and was hoping I could get him to lend me his unit so I could do a write-up for Dusty but unfortunately he sold it years ago complete with the only other existing Romdos/80
cheers

 

[shyandrewt]

@Gazza that manual is gold! Very much appreciated. I've already had a quick read through. The section on FDDs is quite interesting, but will prob. require me to have a second read. I didn't quite understand your comments re 'Dusty' - I'm pretty green here.

 

[Gazza]

Dusty runs a TRS-80 newsletter, well worth a look, link below
cheers

Home

 

[shyandrewt]

Had a quick look, @Gazza - Hours of fun reading there. A fantastic resource, Thanks.

 

[tezza]

Thanks for sending that manual through @Gazza. I don't think I've seen it before, but I need to check my files. I'll let you know.