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TRS 80 Model 4 Engineering Sample


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  TRS 80 Model 4 Engineering Sample by Bill Degnan - 06/06/2005 16:15
TRS 80 Model 4 "engineering sample" submitted for FCC approval. Unit contains a number of non-standard components and a non-standard keyboard.

I was lucky enough to be given the an engineering sample TRS 80 Model 4 submitted for FCC approval. The engineer was Roy Soltoff. Roy also gave me a lot of notes, and the blue prints. There is no s/n. See pics

  TRS 80 Model 4 Engineering Sample Update by Bill Degnan - 07/07/2013 18:46
TRS 80 Model 4 8709296 Rev N/C
Sub-section of the underside of the TRS 80 Model 4 motherboard that was submitted for FCC approval. Note the Rev is 8709296 N/C, indicating a non-production model. Click image for larger view.

TRS 80 Model 4 RAM modifications
It appears that Roy Soltoff held onto the unit after testing was completed and kept it for every-day use or testing purposes. This photo shows his work to up the RAM by bridging with an Alpha Technology RAM board (see below). At some point Roy attached a "128K RAM" sticker to the front under the (disconnected) reset button. Click image for larger view.

Photo of the front side, lower left of the motherboard. Note the Alpha Technology RAM expansion daughter board added by Roy Soltoff some time around 1985. Click image for larger view.

If you're wondering, this system still works very well and so far no problems. I am not a big fan of glare guards, but I will leave this on in place. Note that Roy upgraded the drives to use double sided disks. The lower drive is an MPI model 52, and the top is a Tandon 100-2A. No way to know whether there were drives in the original unit as it was submitted to the FCC.

In addition to the blueprints of the Model 4, Roy also gave me a lot of documentation, notes, and correspondence. I am working to catalog these items.

Next I intend to dump a memory map.

Updated Photos

  Tandy 3 chassis by Bill Degnan - 07/12/2013 14:46
Check out this video:

If you compare the keyboard of the Tandy 3 with the FCC evaluation unit pictured above, it appears as if the Tandy 3 case was probably used to house what was then the new TRS 80 Model 4. The name "Tandy 3" is a late model TRS 80 Model III, perhaps intended for the schools/education market

It is very possible that Roy Soltoff stuck the "TRS 80 Model 4" plate to the computer from some other system at the same time he put the 128K stick on the keyboard. These very possibly were not present when submitted to the FCC for testing. No way to know.

The FCC warning label is the only marking on the bottom of the unit.



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