The Digital Group Phideck

An extraordinary oddity among hobby computers in the 1970's, the Phideck system from The Digital Group was a computer controlled data drive, nearly identical in function to the familiar old tape drives used with main-frame computers of yesteryear. Although several microcomputers of the time could start or stop an associated cassette tape, DG systems actually controlled every aspect of the drive in the same way as mainframes of the day controlled large tape drives, or in similar fashion to how your PC might control a disk drive--no intervention on your part is needed to save or load a file other than to request the file by name. This meant that a DG user had up to a megabyte of online storage available from a single Phideck controller, using 30 min. data cassettes. This was unheard of capacity even for disk drives of the time, albeit considerably slower than a disk, the access time to any file was advertised to be less than 20 seconds. Not bad for a tape system, eh?

With a DG computer running the Phimon operating system, a user could switch on the power and have the operating system up and running in ten to thirty seconds. This was at a time when many microcomputers required about a hundred lines of binary code be toggled in by front panel switches in order to get a paper tape reader or cassette tape to load an operating system. True, disks were becoming available around this time, but you needed a butt-load of cash to own one! (Altair users could pick up a 300k disk drive for a mere $1480 in kit form -- that's $5600 in today's dollars.)

Well, that was the theory, anyway. Reality was a little different. The Phideck had a few design shortcomings that made using it a little less than trouble free--It was possible to make the system work, but it was difficult for the average hobbyist to get it running. ANY noise was fatal to the operation of the system, and noise in a DG computer was a given. This meant that owners were constantly chasing problems.  So what gives? Why the trouble? Well, for one thing, the signals to and from the data cassette drives were unbuffered at the drive--these signals were expected to travel through the interconnecting cables between cabinets without any signal amplification at all! (For those of you not acquainted with electronics, this is akin to trying to hear a quiet conversation in a noisy restaurant from across the room.) This was only one of the problems. All manner of solutions were proposed for all sorts of envisioned culprits, but in the end, the most effective solution was to buy a disk drive!
 

Phimon and Phimon 2 made owning a computer really fun!!

See my Documentation and Software pages for the downloadables.

My Phideck System

I have several of the interface cards and a few of the cabinets with drives and even a couple spare drives that I have collected over the years. At this time, I have only one system that I am actively working on, the dual deck system shown in these photos.

After living with numerous data crashes from the decks, I finally threw my hands in the air and decided to move the controller board into the Phideck cabinet and shorten the lines from the tape heads as short as possible. The controller board is hinged to allow it to flip up, and it is socketed to allow for easy removal from the cabinet. I think it looks pretty good, almost as if it were intended to be this way. :) I also plan to implement many of the hints from Hughie's Hot Tips #2, one at a time, beginning at the least intrusive. (I want to keep my system as original as possible -- but still have it work!)

I still have to rewire the system cabinet to accept the new interconnection cable, and then I will need to track down all the things I forgot to do(!), as always. Yeah, it's a hobby, and yes, I'm having fun. But you'd think I'd have it up and going by now, wouldn't you? Well. I'm not losing any sleep over it, but I will make it work--eventually!! Today, I'm too tired--the kids are fighting over the Wii, I gotta run...

Wish me luck.

 Restoration

I did my standard restoration on this with the cabinet and electronics. (If you don't know what I mean by that, check a few of my other pages! :) The Phideck cabinets in these photos were all in good condition, so mostly just a good cleaning was needed with some minor paint touch-ups. The Phidecks themselves, needed some deeper cleaning and replacement of all the belts. I tracked down a local electronics place with a small supply of belts, and bought out their entire stock. It was just enough for the decks I have on hand. Last time I checked, you could still order belts on the internet from a few places, but get 'em while you can! Somehow, I suspect they may be harder to find as time moves on.

The pinch rollers were all in good shape, but in need of some rubber restorer. I use MG Chemicals 'Rubber Renue', found at the local Fry's Electronics or at CircuitSpecialists.com. This stuff revitalizes the rubber and makes it swell a little. Whatever you do, don't use it on the belts, or you'll need to buy new belts!