6 Aug
2002
6 Aug
'02
10:32 p.m.
I am trying to get a TRS-80 Model III working. When I turn it on the disk
drive spins for a while looking for a disk I presume. All I get on the
screen are wispish diagonal lines as if the horizontal hold is all
whacked.
I managed to unstick one of the video adjustment knobs on the left
underside but all it does is affect the brightness level. The other one
requires a screwdriver to move at all (shimmying it up and down) and does
not seem to affect the display. I haven't opened it yet to see what
adjustments are inside. I'd rather not, but there don't seem to be any
adjustment pots accessible from outside the case.
What's weird is that I have access to a bunch of TRS-80 Model 3's here at
the ACCRC and pretty much all of the ones I have played with so far are
basically "dead" in this manner. The one I'm working on just came in
today and is in the same state. Also, the video knobs on the left
underside are all stuck on everyone I've tried to get working. What is
the deal with that? Do they get rusted over time or something? Very
annoying.
The fact that the disk drive spins up when I turn it on is a good sign I
hope.
Any help on this would be appreciated. I know next to zero about the
TRS-80 series.
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
* Old computing resources for business and academia at www.VintageTech.com *
6 Aug
6 Aug
10:50 p.m.
Sellam,
Are the boot straps on eproms on the motherboards??? You may be facing
possible bitrot, that's one possibility.
Curt
----- Original Message -----
From: "Sellam Ismail" <foo(a)siconic.com
To: "Classic Computers Mailing List" <cctalk(a)classiccmp.org Sent: Tuesday, August 06, 2002 3:31 PM
Subject: TRS-80 Model III
I am trying to get a TRS-80 Model III working. When I turn it on the disk
drive spins for a while looking for a disk I presume. All I get on the
screen are wispish diagonal lines as if the horizontal hold is all
whacked.
I managed to unstick one of the video adjustment knobs on the left
underside but all it does is affect the brightness level. The other one
requires a screwdriver to move at all (shimmying it up and down) and does
not seem to affect the display. I haven't opened it yet to see what
adjustments are inside. I'd rather not, but there don't seem to be any
adjustment pots accessible from outside the case.
What's weird is that I have access to a bunch of TRS-80 Model 3's here at
the ACCRC and pretty much all of the ones I have played with so far are
basically "dead" in this manner. The one I'm working on just came in
today and is in the same state. Also, the video knobs on the left
underside are all stuck on everyone I've tried to get working. What is
the deal with that? Do they get rusted over time or something? Very
annoying.
The fact that the disk drive spins up when I turn it on is a good sign I
hope.
Any help on this would be appreciated. I know next to zero about the
TRS-80 series.
Sellam Ismail Vintage Computer
Festival
--------------------------------------------------------------------------
----
International Man of Intrigue and Danger
http://www.vintage.org
* Old computing resources for business and academia at
www.VintageTech.com *
7 Aug
7 Aug
7:12 p.m.
On Tue, 6 Aug 2002, Curt Vendel wrote:
Are the boot straps on eproms on the
motherboards??? You may be
facing possible bitrot, that's one possibility.
Er, huh?
:)
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
* Old computing resources for business and academia at www.VintageTech.com *
6 Aug
6 Aug
11:25 p.m.
Sellam:
I *think* that what you're seeing with the disk drives
is standard normal behavior. If there's a bootable
disk in the drive it'll load the DOS, if there's a
data disk there it may put out a message complaining
about it, but no disk may do nothing at all.
Normally under these circumstances you'd put the disk
in the drive and press the RESET button (not power
cycle), tho you could certainly cycle power too.
It's been a long time since I used a Model III. My
Model 4 will I think do what you describe (it's buried
at the moment or I'd check it now). Also, last I used
it my Model 4's brightness/contrast controls are still
working, but they may be different from the Model
III's hardware.
-- Frank
--- Sellam Ismail <foo(a)siconic.com> wrote:
I am trying to get a TRS-80 Model III working. When
I turn it on the disk
drive spins for a while looking for a disk I
presume. All I get on the
screen are wispish diagonal lines as if the
horizontal hold is all
whacked.
I managed to unstick one of the video adjustment
knobs on the left
underside but all it does is affect the brightness
level. The other one
requires a screwdriver to move at all (shimmying it
up and down) and does
not seem to affect the display. I haven't opened it
yet to see what
adjustments are inside. I'd rather not, but there
don't seem to be any
adjustment pots accessible from outside the case.
What's weird is that I have access to a bunch of
TRS-80 Model 3's here at
the ACCRC and pretty much all of the ones I have
played with so far are
basically "dead" in this manner. The one I'm
working on just came in
today and is in the same state. Also, the video
knobs on the left
underside are all stuck on everyone I've tried to
get working. What is
the deal with that? Do they get rusted over time or
something? Very
annoying.
The fact that the disk drive spins up when I turn it
on is a good sign I
hope.
Any help on this would be appreciated. I know next
to zero about the
TRS-80 series.
Sellam Ismail
Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger
http://www.vintage.org
* Old computing resources for business and academia
at www.VintageTech.com *
=====
= M O N T V A L E S O F T W A R E S E R V I C E S P. C.=
Clayton Frank Helvey, President
Montvale Software Services, P. C.
P.O. Box 840
Blue Ridge, VA 24064-0840
Phone: 540.947.5364 Email: msspcva(a)yahoo.com
============================================================
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7 Aug
7 Aug
8:04 p.m.
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6:16 a.m.
What happens if you press the <Break> key down while powering up...it
should take you into ROM Basic with a "cass?" prompt.
I grew up with a Model III and it's been a while, but I don't remember
there being an error message if it doesn't find disk in the drive.
Matter of fact I don't remember any text error messages from the boot
loader.
If you can get into ROM Basic, it probably means you have a bad boot
disk.
-Chandra
-----Original Message-----
From: cctalk-admin(a)classiccmp.org [mailto:cctalk-admin@classiccmp.org]
On Behalf Of Sellam Ismail
Sent: Tuesday, August 06, 2002 3:32 PM
To: Classic Computers Mailing List
Subject: TRS-80 Model III
I am trying to get a TRS-80 Model III working. When I turn it on the
disk
drive spins for a while looking for a disk I presume. All I get on the
screen are wispish diagonal lines as if the horizontal hold is all
whacked.
I managed to unstick one of the video adjustment knobs on the left
underside but all it does is affect the brightness level. The other one
requires a screwdriver to move at all (shimmying it up and down) and
does
not seem to affect the display. I haven't opened it yet to see what
adjustments are inside. I'd rather not, but there don't seem to be any
adjustment pots accessible from outside the case.
What's weird is that I have access to a bunch of TRS-80 Model 3's here
at
the ACCRC and pretty much all of the ones I have played with so far are
basically "dead" in this manner. The one I'm working on just came in
today and is in the same state. Also, the video knobs on the left
underside are all stuck on everyone I've tried to get working. What is
the deal with that? Do they get rusted over time or something? Very
annoying.
The fact that the disk drive spins up when I turn it on is a good sign I
hope.
Any help on this would be appreciated. I know next to zero about the
TRS-80 series.
Sellam Ismail Vintage Computer
Festival
------------------------------------------------------------------------
------
International Man of Intrigue and Danger
http://www.vintage.org
* Old computing resources for business and academia at
www.VintageTech.com *
7:14 p.m.
On Wed, 7 Aug 2002, Chandra Bajpai wrote:
What happens if you press the <Break> key down
while powering up...it
should take you into ROM Basic with a "cass?" prompt.
Nope, still no video. The video is hosed. Along with the rest of the
units I've tried.
Now I know why stuff like TRS-80s and C64s were so derided back in the
day: the shit just don't last!
On the other hand, I've rarely met an Apple ][ that didn't boot.
Coincidence? You be the judge.
I grew up with a Model III and it's been a while,
but I don't remember
there being an error message if it doesn't find disk in the drive.
Matter of fact I don't remember any text error messages from the boot
loader.
If you can get into ROM Basic, it probably means you have a bad boot
disk.
Well, I have no boot disk. I'm trying to see if this machine works.
Apparently it does to an extent but the video definitely has a problem.
Nobody knows how to fix this?
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
* Old computing resources for business and academia at www.VintageTech.com *
8:13 p.m.
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11:30 p.m.
On Thu, 8 Aug 2002, Tony Duell wrote:
No, I'm not. Good point. I think I'll work the key or clean it as Fred
suggests and see where that leads.
That's probably true. I was just in a very ornery mood when I wrote that
after unsuccessfully trying to get a TRS-80 Model III, a Commodore 64, and
an Atari 800 working without success.
Nope, still no
video. The video is hosed. Along with the rest of the
units I've tried.
Are you sure it's not the BREAK key? I have had bad keyboard contacts on
M3 keyboards... Also, it is possible to set the external controls so
that the video is
invisible (absolutely no video signal at all). After holding down break
and pressing reset, fiddle with the video controls.
I have the brightness set very high so I can see any text that may pop up
on the screen, but I still think the horizontal hold needs adjustment
before I'll see anything legible.
On the other
hand, I've rarely met an Apple ][ that didn't boot.
Coincidence? You be the judge.
Odd.... I've never had a TRS-80 that's failed to boot (other than needing
cleaning of external connectors). I've had plenty of Apple ][ problems.
Perhaps it's just that I know the TRS-80 better, I have all the service
manuals to hand, so if i have even minor problems I know what to look for
and how to prevent said problems becoming major ones. Well, I have the M3 service manual alongside me, but
since the fault you
describe could be caused by hundreds of things, you've not given me much
to go on. Do you have a multimeter? A logic probe? A 'scope?
Yes, no, yes, but I'll try the simple suggestions first before we have to
go that route.
Thanks!
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
* Old computing resources for business and academia at www.VintageTech.com *
8 Aug
8 Aug
6:54 p.m.
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7 Aug
7 Aug
8:14 p.m.
On Wed, 7 Aug 2002, Sellam Ismail wrote:
Actually, I rarely encounter a stored Apple ][ (or ][+) that will boot
until I press down on each and every chip to get through the corrosion of
the cheap sockets.
That is EXACTLY the same problem as most of the TRS-80s!
Just like Apple, they cut too many corners on connector quality. Cleaning
connections will usually get them working. In addition, some of the
TRS-80 keyboards (there are a couple of different types) won't work after
extended storage unless you open them up and clean them (or just work the
keys A LOT). A Rochester Dynatyper or KGS80 keyboard actuator works great
for that (a box of solenoids that was intended to sit on a typewriter
keyboard to substitute for a printer)
What happens
if you press the <Break> key down while powering up...it
should take you into ROM Basic with a "cass?" prompt.
Nope, still no
video. The video is hosed. Along with the rest of the
units I've tried.
Now I know why stuff like TRS-80s and C64s were so derided back in the
day: the shit just don't last!
On the other hand, I've rarely met an Apple ][ that didn't boot.
Coincidence? You be the judge. Well, I have no boot disk. I'm trying to see if
this machine works.
Apparently it does to an extent but the video definitely has a problem.
Nobody knows how to fix this?
Once you've cleaned the connector contacts, ...
If it still won't work, then better ask Tony!
--
Grumpy Ol' Fred cisin(a)xenosoft.com
10:27 p.m.
At 09:13 08/07/2002 -0700, you wrote:
Nope, still no video. The video is hosed. Along with
the rest of the
units I've tried.
Now I know why stuff like TRS-80s and C64s were so derided back in the
day: the shit just don't last!
Every machine has it's pros & cons... the video memory mapping that seemed
to defy logic on the Apple ][s is one of the main reasons why I never stuck
with them...
Honestly, I don't think I *ever* had a Tandy CoCo, no matter where I got
it, no matter what shape I got it in, that didn't boot first time up; IIRC
I had a floppy drive controller that on occasion might hiccup every 1/4th
boot every couple years; pull 1 screw, reseat chips, reassemble, good for a
couple more years. The beauty of that controller was this: if it was wonky,
it wouldn't survive the boot to OS-9. If the OS booted, it would work
flawlessly until the next reboot, even if it was days later... I still have
no idea how the chips "knew" to "hold on, dammit, hold on!" - but I
never
lost a single bit.
Oh, and I had one CoCo2 that I got from a garage sale would miss around 1/2
of the characters typed on the keyboard, but I'm sure that the 1/4 cup of
sand that I extricated from the keyboard during the re-build had nothing to
do with it... (worked flawlessly after that...)
Maybe Tandys just don't like you??? ;-)
Laterz,
Roger "Merch" Merchberger
10:40 p.m.
Hmmmm.
You need to either have a boot disk in the drive (you said that you didn't
have one), or press the break key when booting to get video.
If that isn't working, the video might actually be bad, or the break key
may be non-functional. If it is the brass contact type, pull the keytop
and clean it. Or press it a few hundred times. If that works, you may
need to exercise the rest of the keys. See if Frank has my old centronics
KGS80. Put it on the keyboard and dump this list through it.
11:44 p.m.
On Wed, 7 Aug 2002, Fred Cisin (XenoSoft) wrote:
See if Frank has my old centronics KGS80. Put it on
the keyboard and
dump this list through it.
That would probably just pollute its mind, making matters much worse.
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
* Old computing resources for business and academia at www.VintageTech.com *
11:43 p.m.
On Wed, 7 Aug 2002, Roger Merchberger wrote:
Every machine has it's pros & cons... the
video memory mapping that seemed
to defy logic on the Apple ][s is one of the main reasons why I never stuck
with them...
Actually, it's entirely logical, if you're a computer :)
The problem is not the non-sequential graphics screen layout (easily
fixed with an index-referenced memory map) but the fact that you must do
all the graphics processing in between regular code unlike on other
systems that had a dedicated graphics chip. Ditto for the sound
generation. Which makes games that were developed on the Apple ][ all
the more impressive. The code to pull off really slick games had to be
tight and clever. Therefore, Apple ][ programmers make better overall
coders (in my not-at-all-humble opinion :P )
Honestly, I don't think I *ever* had a Tandy CoCo,
no matter where I got
it, no matter what shape I got it in, that didn't boot first time up; IIRC
In my experience I'd have to agree with that assessment.
I had a floppy drive controller that on occasion might
hiccup every 1/4th
boot every couple years; pull 1 screw, reseat chips, reassemble, good for a
couple more years. The beauty of that controller was this: if it was wonky,
it wouldn't survive the boot to OS-9. If the OS booted, it would work
flawlessly until the next reboot, even if it was days later... I still have
no idea how the chips "knew" to "hold on, dammit, hold on!" - but I
never
lost a single bit.
I don't think I've ever had an Apple ][ disk controller failure of any
kind. With only 7 ICs there wasn't much to go wrong :)
Maybe Tandys just don't like you??? ;-)
Not Tandys, Radio Shacks (and Commodores, and Ataris... :)
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
* Old computing resources for business and academia at www.VintageTech.com *
28 Aug
28 Aug
11:40 a.m.
New subject: Apple II hi-res and DRAM refresh (was RE: TRS-80 Model III)
--- Roger Merchberger <zmerch(a)30below.com> wrote:
Every machine has it's pros & cons... the
video memory mapping that
seemed to defy logic on the Apple ][s is one of the main reasons why
I never stuck with them...
With my early experience having come from the Commodore world, I admit
that the hi-res mapping on the Apple ][ struck me as odd, too; but when
I programming professionally on it, our graphics guru whipped up a fast
and simple row->address lookup routine and we didn't have to worry about
it from an application standpoint.
The "logic" is that the video refresh circuit doubles as a DRAM refresh
counter. By decoupling the sequential nature of the CPU's view of the
hi-res page and the video output circuit's view of the same memory,
the timing lines up and results in a simpler refresh circuit (i.e., you
don't have to refresh every byte in a DRAM chip, just every row, every
so often; the mapping is driven by the bit geometry of the 4116 DRAM
and how many columns there are per row). I forget how many chips Woz
saved, but I think it was between 1 and 4.
-ethan
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1:22 p.m.
New subject: Apple II hi-res and DRAM refresh (was RE: TRS-80 Model III)
On Wed, 28 Aug 2002, Ethan Dicks wrote:
With my early experience having come from the
Commodore world, I admit
that the hi-res mapping on the Apple ][ struck me as odd, too; but when
I programming professionally on it, our graphics guru whipped up a fast
and simple row->address lookup routine and we didn't have to worry about
it from an application standpoint.
Yes, it adds a few cycles to the plotting of points, and it is quite lame,
but we must look at the history of why it is like this, as Ethan describes
below.
The "logic" is that the video refresh
circuit doubles as a DRAM refresh
counter. By decoupling the sequential nature of the CPU's view of the
hi-res page and the video output circuit's view of the same memory, the
timing lines up and results in a simpler refresh circuit (i.e., you
don't have to refresh every byte in a DRAM chip, just every row, every
so often; the mapping is driven by the bit geometry of the 4116 DRAM and
how many columns there are per row). I forget how many chips Woz saved,
but I think it was between 1 and 4.
Woz was all about efficiency in design: a true hacker. The hack was very
clever for the day (1977) and saved on chip costs, which were still high
back then. Also, Woz believed that anything that could be done in
software should, and stuck with a minimalist hardware design attitude.
Yes, it's totally lame to those who came up on computers with normal,
sequential graphics screens, but as Ethan mentioned, a simple look-up
table (consisting of $180 bytes) and some convenient 6502 opcodes (load
accumulator indirect indexed) fixes the problem quite nicely and easily.
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
* Old computing resources for business and academia at www.VintageTech.com *
7 Aug
7 Aug
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17 comments
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ard＠p850ug1.demon.co.uk -
cbajpai＠attbi.com -
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curt＠atarimuseum.com -
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