Tandy/Radio Shack TRS-80 Model 4

From: John Honniball <John.Honniball_at_uwe.ac.uk>
Date: Fri Jul 28 10:20:21 2000

Having just reassembled a TRS-80 Model 4, I must have a
quick rant about the way this machine is put together. If
anything, it'll be a guide to future Model 4 owners (and
the Model 3, presumably).

I started off with a working machine but no boot disk. The
message I got from the corrupt disk supplied was "ERROR".
That's it, no more explanation, just one word.

I was lucky enough to find a manual and a boot disk in a
secondhand bookshop here in Bristol. So, I decided to try
the machine again, but I didn't want to trash the new disk
in a faulty drive (see, Tony, somebody's listening!).

Take care when opening up the Model 4 because the CRT comes
off with the lid, making it heavy and off-balance. The back
end of the CRT (with the connector on) is very close to the
internal metalwork of the chassis, too, so don't lift the
lid off backwards. And don't forget to remove the single
bolt from the top of the back of the lid.

To get the drives out, you have to remove four bolts per
drive. Top drive first, fiddle about with the cables, then
the lower (drive 0). All seemed to be OK, so I tried to
get them back in again. Turns out that you can't get the
bolts back in without removing the power supply PCB.

So, with the drives back in, I powered it up. No screen
display at all, no "ERROR", nothing. Damn. After a while
checking IC sockets and tracing video signals, I put the
dud disk back in and got "ERROR", nice and clear on the
green screen. You don't get any error message at all if
there's no disk in the drive.

Now I tried the new boot disk, and sure enough, it worked!
First task, set the system date. According to the manual,
it only accepts dates up to about 1987! Next, copy that
good boot disk before I do something daft to it. I used
the "backup" command, followed the prompts and... it
failed. The new-looking disk actually has some blemishes
on the oxide surface where it's been stored for so long.

Oh, and if you try to boot a non-bootable disk, you get a
nice friendly message about that disk being a data disk --
now why couldn't they make it say something when there's NO

Finally, the serial port, external floppy disk port and
expansion connectors are "convieniently located" on the
underside of the machine.

John Honniball
Email: John.Honniball_at_uwe.ac.uk
University of the West of England
Received on Fri Jul 28 2000 - 10:20:21 BST

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