TRS-80 Model III drive probs
Frank Traut
Just acquired a Model III and DD 1 is giving me some problems.
I do a little bit of electronics work, so thought I'd give it a
shot. Touched up the cold solder on the power connector and she
sprang to life. Well, sort of. The drive gave me all sorts of
trouble reading disks until I played around with the tiny blue
pot that sounds as if it controls the speed. Having gotten the
drive into the closest spec I could (it read the directory and
booted MOST programs off the disk), the frickin' motor died on me!
Or... the TIP 110 transistor went. I desoldered her and took some
readings off my DMM. It does indeed appear fried. Off to RatShack,
only to find that's probably something else they no longer carry. lol
Having said that, I just looked and an NPN TIP 120 looks like she'll
do the trick.
Still... got me to wondering: can you set up a RAM disk of sorts
on the TRS-80's? One could get away with 1 drive if you threw the
contents of LDOS into RAM, wrote an assignable and then stuck in
your program disk. Not every single Model III had 2 drives, did they?
There's got to be a work-a-round if I can't get this poor thing to
work...
TIA for any help or pointers here.
-Frank
Frank Traut
so at least some of the commands off LDOS could fit while
getting some functionality out of the program disks...
winston19842005
Traut" <ftra...@charter.net> wrote:
You might want to consider an SVD. There was a run recently of them.
They plug directly into your controller and mimic the drive. And they have
an interface to transfer files to/from PCs. I have an original around here
somewhere.
And I'm sure some of us have spare DD floppy drives. Are yours single-sided
or double-sided? I have a couple of pulls from my Model 4P that were
single-sided half-heights. So you could put two in one drive bay and
something else in the other.
You can always go 3.5", too... Sure there is a faq with this stuff
somewheres...
Frank Traut
> You might want to consider an SVD. There was a run recently of them.
> They plug directly into your controller and mimic the drive. And they have
> an interface to transfer files to/from PCs. I have an original around here
> somewhere.
>
> And I'm sure some of us have spare DD floppy drives. Are yours single-sided
> or double-sided? I have a couple of pulls from my Model 4P that were
> single-sided half-heights. So you could put two in one drive bay and
> something else in the other.
>
> You can always go 3.5", too... Sure there is a faq with this stuff
> somewheres...
Thank you very much for the reply. I did manage to get Drive 1
working.
The transistor on the floppy board WAS bad. Replaced it with a
slightly
heavier duty TIP120 this morning and strobed the motor at 60hz.
Brilliant they taped a timing calibrator under the drive wheel and
a coincidence that I'm an audiophile with a timing strobe. lol
Other than that, a few grounds were bad that I took care of and
I've determined that 2 disks are now totally shot or they somehow
got ruined by my (then) flaky drive. Those disks of course, are the
ones that had all the fun arcade stuff on them :-(
This computer is not going to see a ton of use, but that SVD device
sounds interesting. I just wanted to add it to the small "museum"
I've got going and of course, it has to be 100% functional! Model
III was the first I lost my computer virginity to (we had a long line
of them all networked together in grade school) and thought it would
be neat to tinker around with.
Unfortunately or fortunately (nice to have a backup, but probably over
paid), I just bought an "untested" external Model III drive off ePay.
It's going to set me back about $50 shipped and is a lot more than I
wanted to spend, but like I said; like to have a 100% working unit.
Was
I wrong in assuming I could remove the drive from its case and install
it as Drive 1? Ira mentioned there is a chip or a jumper that changes
drive numbers. Anywho... since I repaired mine. May as well leave the
external one 'external' for now. Might need a cable though for it as
the
one pictured was missing it.
-Frank
-update-
Guess this is not a Model xxx specified drive. Thought I was bidding
on a
Model III or compatible. Would someone please confirm if I can take
the
drive out of an external Colour Computer drive and "plop" it into a
Model
III? Be nice if more people knew what they were selling... or knew
what
they were buying... lol! Hmm....
Frank Traut
> You might want to consider an SVD. There was a run recently of them.
> They plug directly into your controller and mimic the drive. And they have
> an interface to transfer files to/from PCs. I have an original around here
> somewhere.
>
> And I'm sure some of us have spare DD floppy drives. Are yours single-sided
> or double-sided? I have a couple of pulls from my Model 4P that were
> single-sided half-heights. So you could put two in one drive bay and
> something else in the other.
>
> You can always go 3.5", too... Sure there is a faq with this stuff
> somewheres...
Thank you very much for the reply. I did manage to get Drive 1 working.
Knut
model III. Old model I drives are often 35 track where model III would
normally use a 40 track drive.
What drive manufacturer is it and model?
Does it have an RS catalog number?
A 40 track single sided drive I got was a coco drive (I could see from
its RS catalog number). It works nicely with any of my TRS-80s (I,III
and 4).
A model III could of course also work with a 35 track drive but DOS
diskettes for the III are often 40 track disks so you would run into
problems.
And jumpers or jumper blocks are usually no problem. Well marked and
easy to find. Sometimes tandy would jumper all driveselects and use a
cable with "pulled pins" to decide which drive is which. Sometimes only
the driveselct in question was jumpered as well as the "pulled pins"
cable and then you would need to change the jumpers to swap drives. I
prefer cables without "pulled pins" and that the jumpers decide.
If the drive is 35 track formatting 40 tracks would work, kind of, but
those last 5 tracks will end up as bad tracks. Note that model III uses
double density and that double density is a controller feature not a
drive feature. Note also that track spacing and placement is the same
for 35 track and 40 track drives.
Knut
Frank Traut
> What drive manufacturer is it and model?
> Does it have an RS catalog number?
It's a Radio Shack and the cat # is: 26-1160.
> A model III could of course also work with a 35 track drive but DOS
> diskettes for the III are often 40 track disks so you would run into
> problems.
That's what I was afraid of.
> And jumpers or jumper blocks are usually no problem. Well marked and
> easy to find. Sometimes tandy would jumper all driveselects and use a
> cable with "pulled pins" to decide which drive is which. Sometimes only
> the driveselct in question was jumpered as well as the "pulled pins"
> cable and then you would need to change the jumpers to swap drives. I
> prefer cables without "pulled pins" and that the jumpers decide.
>
> If the drive is 35 track formatting 40 tracks would work, kind of, but
> those last 5 tracks will end up as bad tracks. Note that model III uses
> double density and that double density is a controller feature not a
> drive feature. Note also that track spacing and placement is the same
> for 35 track and 40 track drives.
So, assuming this is a Model One, 35 track drive, you're saying that
I could remove it from its case and install it in the model III and
because of the Model III's double density controller, this should work
more or less?
Thanks for the info Knut!
-Frank
asc135
>
> It's a Radio Shack and the cat # is: 26-1160.
>
>
> So, assuming this is a Model One, 35 track drive, you're saying that
> I could remove it from its case and install it in the model III and
> because of the Model III's double density controller, this should work
> more or less?
Once you have the drive, take off the cover. If it is a Shugart
SA-400 then you have a 35 track unit. They're pretty darn useless as
they can't step very fast either (30ms track to track). I have a pair
of those in a Smoke Signal Broadcasting enclosure and I use them for a
Model I when I'm in pure nostalgia mode, including the unreliability
implies. Don't waste your time trying to put it into a Model III.
If you have a Tandon or Texas Peripherals drive, you are all set.
They were all 40 track and could step at 6ms. I think Radio Shack
sold both 35 and 40 track drives as 26-1130 (or maybe they put a
suffix letter to distinguish them... I can't recall).
Another important thing to keep in mind is that the internal drives of
a Model III are not terminated. Some genius decided the internal
cable was short enough to get away with putting the termination right
on the FDC board. If you replace a drive unit make sure any resistor
pack is removed or you will over-terminate the bus and get serious
reliability problems. External drives are terminated more
conventionally (i.e. last drive on the cable). The only weirdness
there is the drive select mapping. External drives are strapped as 0
and 1 to get addresses 2 and 3 respectively.
Amardeep
Frank Traut
transaction. Just going to wait and buy exactly what it is
I need - a Model III 40 track drive. Anyone here have one
in good shape they'd like to sell?
N Morrison
You might want to try the Yahoo groups, TRS-80, ColorComputer etc. I
got my last two drives privately there.
Sadly, the Unimat lathes guys (I'm one) found out that the drive rods
the head runs on are fine as tommy bars for their lathe chucks so they
trash drives to get them for this purpose! Have you tried computer
recyclers BTW?
Neil
ClemFM
Take a look at my post ref the Gotek USB drive replacements i.e. use a
USB thumb drive as a 720K FDD!
Clem
Frank Traut
> Take a look at my post ref the Gotek USB drive replacements i.e. use a
> USB thumb drive as a 720K FDD!
> Clem
Oh wow, thanks for the info! That certainly does look interesting. So,
if I am reading this right, for about $100-$150 - you can get this
USB adapter that plugs into drive 1's cable? Too bad it doesn't fit
where Drive 1 goes, looks like a floppy drive, but with USB input.
I'd still like to find a regular floppy drive if anyone would like to
sell. Would like to keep the system as original as possible and besides,
$150 is more than I'd really like to spend on this system- only to find
it doesn't work as advertised, or you need to buy this, install that,
etc. That's been my luck lately with just about every retro computer
purchase lately. ;-)
-Frank
Frank Galphin
"Frank Traut" <ftra...@charter.net> wrote in message
news:q1AZl.25289$IP7....@newsfe23.iad...
Just as a note. When IBM released the Original PC they used Tandon
double sided double density drives that were full height. I have used
these before and they are great replacements. Although they have
the "IBM" logo on the front bezel. If you can find a couple of these
you would be in good shape. Or you could also use Teac FD5x series
of half height DS/DD drives they too work great just that you need to
use a standard FDD cable and not the TRS-80 cable which has
pins pulled for drive selection. The FDD cable thing also applies to
the IBM drives. What I did was butcher an old PC cable and made
my own cable up with 3 card edge type connectors. Drive select
is handled by the drives this way.
Here is an ebay link at 25.00 a piece not to bad.
http://cgi.ebay.com/TEAC-FD-55-F-5-Floppy-Drive-NR_W0QQitemZ270399458366QQcmdZViewItemQQptZPCC_Drives_Storage_Internal?hash=item3ef5104c3e&_trksid=p3286.c0.m14&_trkparms=65%3A12%7C66%3A2%7C39%3A1%7C72%3A1205%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50Hope this helps.Frank G.