23 Oct
2007
23 Oct
'07
6:03 p.m.
I've decided to make a couple serial boards for my Radio Shack PT210
terminals so I can have them talk serial. How many people here have
PT210s who'd like a serial board?
--
David Griffith
dgriffi at cs.csubak.edu
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?
24 Oct
24 Oct
12:46 a.m.
David Griffith wrote:
I've decided to make a couple serial boards for my
Radio Shack PT210
terminals so I can have them talk serial. How many people here have
PT210s who'd like a serial board?
I would like one. Also, this weekend I found on Craigslist, an IBM 5100.
When I picked it up,
I was offered a Radio Shack TRS-80 model one and a model 4. The model 4
powers up and
asks for a diskette. The model one has the expansion box and disk but I
don't know which connectors
to hook the stuff up to. Do you know where I can get a boot disk for the
model 4 and manual for the
model one? Or a web site that shows the connections?
Thanks,
Bob
4:24 p.m.
On Tue, 23 Oct 2007, Bob Rosenbloom wrote:
David Griffith wrote:
The board is about 3 inches by 2 inches, double-sided, and without
soldermask or silkscreening. That brings it to maybe $10 each if I do a
run of five. All the other parts are easily available from Mouser or
Jameco including the 4PDT push-push switches. I got the schematics and
foil patterns from the PT-210 service manual. I'll post a formal BOM
later this week.
I'd like to send off the order by Friday next week, so if anyone else
wants one, please let me know by then. I won't ask for any money until I
have the boards in my hands.
--
David Griffith
dgriffi at cs.csubak.edu
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?
I've decided to make a couple serial boards
for my Radio Shack PT210
terminals so I can have them talk serial. How many people here have
PT210s who'd like a serial board?
I would like one. 
5:59 p.m.
I was offered a Radio Shack TRS-80 model one and a
model 4. The model 4
powers up and
asks for a diskette. The model one has the expansion box and disk but I
don't know which connectors
to hook the stuff up to. Do you know where I can get a boot disk for the
model 4 and manual for the
model one? Or a web site that shows the connections?
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
As regards the OS, there were basically 2 options. One was the TRS-DOS
6.x / LS-DOS 6.x, The other was CP/M. I have no idea where you'd find the
latter (or indeed _why_ you'd want to find it, LS-DOS being a much nicer
OS), but I got the former from Tim Mann's site. If you can't find it
anywhere, I suppose I could send you the image I downloaded.
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.
Now, going round the card edge fingers, starting at the centre front and
going clockwise, we have :
Front Centre (40 way) : Connected to the optional I/O board. Normally not
used.
Front Left (40 way) : System bus input from the CPU. How this is
connected depends on the revision of the EI. The latest one (which is
what I have) just uses a straight-through ribbon cable. Earlier ones had
a special 'buffered cable' with a box containing buffer chips in the
middle. This cable is marked to say which end connects to what. Some
early versions _also_ had a DIN cable soldered to the EI and the CPU, you
just plug those together.
Left Front (40 pins) : Buffered system bus output to other devices.
Normally not used
Left Rear (34 pins) : Parallel printer. Straight-trhough ribbon cable to
a 36 pin microribon plug to a Centronics printer
Rear left (34 pin) : Disk drives. Normal SA400 pinout to 5.25" drives.
Model 1 TRS-DOS only supports single-sided drives (and the normal
hardware only supports signle density (FM) operation. There were add-on
boards normally called doublers' to do MFM recording. Other OSes (my
favourite was LDOS) would use said doublers, and would also let you use
double-sided drives.
On the rear are 3 DIN sockets. You can ignore these. They connect to an
internal relay to select between 2 cassette recorders, one to each of 2
of the socekts and then a striaght-through DIN cable to the CPU cassette
socket. I cna never remember the order.
-tony
25 Oct
25 Oct
12:54 a.m.
New subject: TRS-80 mdls 1 & 4
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
4:18 p.m.
New subject: TRS-80 mdls 1 & 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
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.
It is,. of course, bank-switched, along with the 14K BASIC ROMs and the
(2K) video memory.
IIRC, TRS-DOS only used 64K for running programs. The other 64K can be
used as a RAM disk.
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
11:44 p.m.
New subject: TRS-80 1 & 4 also: Help with IBM part numbers and schematics for the 5100
Tony Duell wrote:
You still want to get a boot disk, so you cna use the
disk drives, etc.
Most PC controllers can write the TRS-80 format (you should use a 360K
drive in the PC, BTW, the TRS-80 uses 40 cylinder disks normally).
Got some DOS disk from TRS-80.com and the systems works fine.
That's very unusual. That sounds like the typical
behaviour of an SMPSU
that's detecting a problem and shutting down, but of course the M1 supply
is a linear one. This _is_ the origianl supply, right?
-tony
It's an original RS black brick, analog type power supply. I'll look
into this over the weekend.
Now, yet another problem.
On the IBM 5100 system I got, there is a problem with the keyboard. If
you press the shift key (either one)
or the command key, they act as if they are stuck down. Not
mechanically, but logically. I took the keyboard
apart, it's an interesting design. The key switches are a capacitive
type, but operate in the reverse of other
keyboards of that type I have seen before. All of the key switches are
pressed down in the "open" position.
When you press a key, the capacitive plate moves away from the pads on
the PCB.
I swapped key switches around and the problem stays with the shift and
cmd keys. After downloading the
maintenance manual from bitsavers.org, its clear that those keys control
latches that change the key codes.
There is a logic diagram, but not a real schematic. I believe the IC's
are all TTL type, they are all made by
TI or National, but all are IBM house numbered. Before I start to trace
out the logic, does anyone have
a cross reference for IBM IC numbers to industry standard numbers?
Anyone with a real schematic that
shows pin numbers on the IC's?
Thanks,
Bob
26 Oct
26 Oct
7:13 p.m.
New subject: TRS-80 1 & 4 also: Help with IBM part numbers and schematics
[M4]
Got some DOS disk from TRS-80.com and the systems
works fine.
Excellent.
Incidentally, you can also boot any Model 3 OS (or self-booting disk,
or...) on the Model 4. You'll have a 64*16 display, like a M3, and 48K
RAM, but it does work (and was designed to work).
[M1]
It's an original RS black brick, analog type power
supply. I'll look
into this over the weekend.
It's been a long time since I've been inside an M1, but I remmber some of
it. The PSU has a cnetre-tapped AC output used for the +12V ad -5V
supplies and am unsmoothed DC output (it's another centre-tapped winding
with a couple of dfodes inside the power brick) for the +5V. All
smoothing is on the CPU PCB. The +12V and +5V regulator circuits use the
well-known 723 chip, and are linear supplies. The -5V supply is a simple
zener diode + resistor circuit.
I wonder if for some unknown reason the machine suddently draws too much
current from one of the supplies about 1s after reset. And that shuts the
supply down, it then tires to restart onlg for the prolem to repeat. I
can't think what would do that, though. But the prolem might not be in
the PSU area.
-tony
6186
days inactive
6189
days old
7 comments
3 participants
participants (3)
-
ard＠p850ug1.demon.co.uk -
bobalan＠sbcglobal.net -
dgriffi＠cs.csubak.edu