The Mini Bytemaster

Introduced in February of 1978, The Digital Group Mini Bytemaster was a fully integrated computer system in a single package. This is perhaps the most coveted of all Digital Group systems, and the least likely to ever be owned. This is because, although introduced with great fanfare, the Mini Bytemaster was never widely shipped to customers. According to Robert Suding, DG co-founder and Mini Bytemaster designer, only a few dozen of these machines were ever made. Most were delivered to friends and possibly cash paying customers, but generally, "you had to know somebody to get one". This was the final system designed by the Digital Group just before the demise of the company.

The Mini Bytemaster was essentially a Digital Group Z80 computer system packaged with a single internal mini-floppy (5-1/4") drive of 160 K byte formatted capacity, and a high resolution 9" video monitor. The machine also sported the newly designed DG motherboard with improvements that made adding interface cards a little less painful, as the interconnecting lines for popular cards were already in place, and headers for interface cables were part of the board layout. The previous DG motherboards required some user wiring to add any new interface cards.
 

My Mini Bytemaster was acquired directly from Dr. Suding in March of 2004, and was his personal machine. This is the actual machine used by Dr. Suding to develop many Digital Group products and software offerings. This is a great little machine, and has quickly become my favorite... next to my original 6800 machine, that is!

As received, the Mini Bytemaster was in operating condition with the exception of the keyboard. The machine was in fairly strong need of cleaning, but otherwise was in good condition. One of the over voltage protection circuits had been disconnected due to a bad SCR, and the video monitor was a bit temperamental, so there was some work to be done with it before it could safely be put to regular use. 

Included with the machine were the following cards: Z80 Processor, a very rare and pretty version of 32K static RAM, two I/O cards, TVC64, HAM card, disk controller, and super bonus... a VOTRAX card! For those who may not know, the Votrax was an early speech synthesis card.

With the Bytemaster, I also received several binders of documentation and a binder full of software on 5-1/4 inch disks, many of which were one of a kinds or original development copies. Coool! After several hours of testing, I found that many of the original disks were unreadable. The majority of titles were fine though, and I have started to make backup copies of all.
 

Photos Prior to Restoration

 
Restoration

Over the next few months I disassembled the machine completely and performed my famous anal-retentive cleaning job on it... My goal was to return the machine to original condition. Basically, this was a full restoration operation, every part was disassembled, repaired as needed, cleaned and touched up. None of the original cabinet paint was altered. 

Restoration was fairly straightforward. Documentation was not available for this machine, so it was important to create some before digging in too far. I drew several diagrams and schematics, and traced out the I/O lines and etc. Mostly though, I took pictures. For some reason, I always forget to write something important down, but with pictures, I can usually go back and check.
 

 
Teardown & Cleaning

After documentation, the next step is the teardown. I pull everything apart and set it all aside. After the entire machine is disassembled, I begin the cleaning process. Everything gets washed and dried, metal parts are buffed, polished, or brushed. Paint is touched up where needed. Soldered connections are inspected and cleaned up as needed. Even the wiring is cleaned for reuse wherever possible. I also disassemble, clean, repair, and pretty-up the power supplies. This is all very time consuming! 

Next, I clean and repair all the circuit boards. The boards of the Bytemaster were in good condition and required only a good cleaning.

The wiring harness was completely rebuilt using as much of the original wire as possible. I clean the wire with a solvent and attach new connectors on the ends. Everything is buttoned down with wire ties, as the original.
 

Reassembly

Now for the fun part! Everything is reassembled as though from a kit. In this case, I had to make things up as I went along, but I've done this before! All went well, and the whole assembly process took only a few hours. 

The paint on the front aluminum piece seen in the photos, hides an original blemish--the plastic front cover was cut too large for the disk drive. This was a simple fix that worked great. Another fix was the addition of a card guide--the Bytemaster as received had none, and the cards were loose and free to rattle around. I felt this was needed, especially since this machine was to make a two thousand mile round trip to the West coast for VCF 7.0.

And now for the photos...