24 Oct
2007
24 Oct
'07
9:54 p.m.
Tony Duell wrote:
Great help! I followed this and it's working! There's a sticker on the
front saying it has 128K of RAM.
Can TR-DOS use all of it? I assume it's bank selected somehow.
I was offered
a Radio Shack TRS-80 model one and a model 4. The model 4
The M4 first :
If you hold down the BREAK key while turning it on or pressing Reset
(Reset == the unmarked recessed button on the keyoard), it'll go into
Cassette BASIC. You'll get a CASS? prompt on the screen. Hit ENTER and
you'll get a MEMORY SIZE prompt. ENTER again and you're in BASIC. Of
course you can't use the disk drives, but at least it'll let you test the
system
For the M1 :
The EI (expansion interfce) is placed with the power button on the front
face and the 2 removable covers on top. The left-hand cover is held on by
4 screws, under that you can put an optional I/O board, normally a serial
port. It's likely to be empty. The right-hand cover is held on by 3
screws and covers a space to fit 2 power supplies, one for the EI and one
for the keyboard/CPU. The 2 supplies are indentical. At the front of this
space, on the PCB at the left side, is a 5 pin DIN socket. That takes the
output cable from the PSU used to power the EI.
Snip..
Again, great help. Mine does have the serial port board, but only one
power supply. I tried the one supply
with the model 1 but the LED on the keyboard flashes about once per
second, and nothing else (monitor
has a slight flicker at the flashing rate.). I downloaded the
schematics and will get to it sometime in the future....
Anyway, the IBM 5100 works except for a keyboard problem (shift and cmd
keys get stuck on after they
are pressed once. Electrically stuck, not mechanical). That along with
the working model 4 is not bad.
Thanks again.
Bob