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View Full Version : model I, expansion unit, percom drives and no where to go



billdeg
April 3rd, 2005, 09:24 AM
I am attempting to get a TRS 80 Model I system up and running. Perhaps I can find advice here on this board.

The hardware:
Model I 26-1006 16K level II (appears to work, can load programs from tape)
Expansion Interface (26-1142-1) (see below *)
2 Percom drives (model ? 9/1979 written inside in pen) 5 1/4"
percom drive separator (installed into expansion interface following directions / 1771 chip etc.)
software including a percom patch pack #4, TRS DOS 2.3.

Situation
Following directions from expansion interface users manual, I have hooked everything up and powered on the system in correct order. The computer asks Memory Size? and the drives spin continuously (when power turned on and cable attached to expansion unit); system does not attempt to boot from disk.

I assume the expansion unit is bad, yes? Am I correct that if I get "Memory Size?" that the expansion unit is not sending a signal to the base keyboard/computer? Does the continuously-spinning drives indicate that there is a missing terminator someplace? Is there a web site that takes a person through a diagnostic routine for percoms expansion units? I suppose that I can test the cassette interface on the expansion unit, have not done that yet.

I would like to first test that the expansion unit works, and then test the diskdrives. How might one test the expansion unit and computer? Is there a memory location or BASIC program that can be entered in to run a self-diagnostic?

*2nd expansion unit
using a second expansion unit with NO drive separator (26-1142-1)...get garbled characters on screen and no memory size?, otherwise same symptoms as above.

Rick Ethridge
April 11th, 2005, 07:13 AM
A properly operating Model I with expansion interface attached and powered up with result in a garbage screen without drives attached and a bootdisk inserted.
Powering up to "Mem Size" indicates your IE is either not running, incorrectly connected or not powered up. To boot with a good IE hold down the "break" key to get "Mem Size".
Pressing the "enter" key will show the start screen and the extra memory. Mine has 32K expansion(maximum).

billdeg
April 11th, 2005, 07:51 AM
Rick,

Thanks. I have learned a lot since I entered this post and should have updated it...The Percom data separator was bad. I replaced it with the original 1771 chip and everything now works. See pics of screen shots...

http://www.vintagecomputer.net/tandy/trs80_1/

Also, I have a great 4-disk tutorial about using the Model 1 with diskdrives, NewDOS, BASIC commands, etc.

I have other disks that appear to require the data separator, so I guess I will try to track down a replacement.

One of the pictures is of a game called "Eliminator" which is the obvious ancestor to the Defender arcade game. Works exactly the same way but in 48 K.

Bill

remi
April 11th, 2005, 10:23 PM
A properly operating Model I with expansion interface attached and powered up with result in a garbage screen without drives attached and a bootdisk inserted.
Powering up to "Mem Size" indicates your IE is either not running, incorrectly connected or not powered up. To boot with a good IE hold down the "break" key to get "Mem Size".
Pressing the "enter" key will show the start screen and the extra memory. Mine has 32K expansion(maximum).

My Model I + extension does exactly this, weither or not the drives are attached (gargabe screen, or boot with 32K memory extension if pressed 'break'
One of the drive rotate for about 2 seconds, but it does not boot on the disk inserted. No error message, just the same garbage on the screen.

Any idea what I should be doing ?

Regards

Rick Ethridge
April 12th, 2005, 10:40 AM
It sounds as if either your boot floppy drive is dead or your boot floppy is unreadable. With the drive spinning the latter is more likely.

Al Hartman
September 8th, 2013, 09:54 AM
This is an old thread, but I found my originals of the Percom Patch Pak #4 and #5. Anyone remember what they do?

Al Hartman
August 29th, 2014, 07:33 PM
I have other disks that appear to require the data separator, so I guess I will try to track down a replacement.

I have a working Data Separator, there doesn't seem to be much to them. It should be easy to repair.

20162

Here is info on the Aerocomp version which should be similar...

http://www.prof-80.fr/separateur-aerocomp

The Aerocomp Doubler should have an external data separator on-board for single density mode. As should the Tandy Doubler.

To use a Tandy Doubler, you need TRS-DOS 2.7DD, MultiDOS, or Newdos/80 zapped to support it. I think there were zaps for later versions of DosPLUS too.

I have copies of most every Model I DOS. If you need any, let me know.