I know this is going to sound crazy but ...
On the M102 system bus connector Pin 1 is marked on the top side
of the connector next to the reset button. That means pin 37
should also be on the top row - second pin on the top row of the
other side near the printer port.
If I probe a machine with a logic analyzer and press reset, pin 37
(RAM RESET) does nothing. It's neither negative or positive. It
is just dead. But if I probe what appears to be pin 37, I get the
expected behavior on the reset button - logic low that then goes
high while the button is being held.
The same thing is happening on pin 32 (RESET). If Pin 1 is marked
correctly then pin 32 should be on the bottom row, That pin is
active and constantly changing state, so it's clearly not reset.
But pin 33 (INT REQ) would have that behavior. Moving to what
should be pin 31 (top row) shows logic low normally and logic high
when I hold the reset button.
Is the IO Bus on my machine wired with the pins already reversed?
On Mon, Nov 18, 2024 at 7:22 PM Jerry Davis <[email protected]
<mailto:[email protected]>> wrote:
Seems to be a cable/connector issue.
I repeated the sequence you described on the M100 and DVI that
I have here and BASIC loads and starts as expected.
I have a ribbon cable with a broken signal pin at the M100 end
and my M100 does what yours does when I use that cable. Which
makes me think you may have a cable problem.
Jerry
On Mon, Nov 18, 2024, 7:20 PM Michael Brutman
<[email protected] <mailto:[email protected]>> wrote:
I powered on the M102 first, then the DVI. After the
copyright message came up I tried the reset button, power
off and then power on, and a cold start. The machine
restarted but the amount of free memory remained the same
and the DVI disk light did not turn on. I'm fairly
certain the DVI is not seeing the reset signal from the M102.
Going to BASIC and using SCREEN 1,1 fails because I'm
still on the built-in BASIC at this point, as DISK BASIC
never got moved into the memory on the M102.
-Mike
On Mon, Nov 18, 2024 at 3:20 PM Jerry Davis
<[email protected] <mailto:[email protected]>> wrote:
After executing the power-on sequence and getting the
"Microsoft" message, did you execute the BASIC command
"SCREEN 1,1" from the Model 102?
The above command switches output to the CRT on the
DVI and displays the key labels at the bottom of the CRT.
Jerry
On Mon, Nov 18, 2024 at 11:39 AM Michael Brutman
<[email protected] <mailto:[email protected]>>
wrote:
I've tried all three methods - power off/power on,
Reset, and cold start. There is no difference.
Also, the two machines have no options or
expansions that would alter their behavior.
The technical service manual has a reasonable
troubleshooting guide which gives specific pins
and behaviors to look at. I'd still like to find
a known good cable before breaking out an
oscilloscope, but at least the schematics and
behaviors are documented.
The length of the cable is kind of freaking me out
a little bit - for a bus that's a long stretch.
Do you know the length of the original factory cable?
-Mike
On Mon, Nov 18, 2024 at 9:19 AM Royce Taft
<[email protected] <mailto:[email protected]>>
wrote:
One other thing you could try is a cold start
(CTRL+PAUSE+RESET). It will wipe all your
102’s memory, but maybe it will help?
Royce
Sent from my iPhone
On Nov 18, 2024, at 08:34, Michael Brutman
<[email protected]
<mailto:[email protected]>> wrote:
I had checked the connectors and pins before
I wrote, and I was even going to check for
continuity on each pin but that's going to
take a while and be error prone with 40
pins. The connector on the underside of the
DVI has the snap-in latches which are
engaging. I can't push any further and I
haven't bent any pins. The cable is new from
Gregory (Arcade Shopper), so I don't have a
lot of reason to suspect it.
Besides trying two different 102s I've also
tried batteries and wall power for the 102s,
and I even upgraded one to max out the RAM
just in case I was missing a memory requirement.
The DVI unit itself was pristine on the
inside when I first looked at it. I'll have
another peek inside to check the connector;
perhaps it experienced some trauma and there
are broken traces on it. But I really don't
want to look for problems where they are
unlikely or fix things that are not broken ..
I've learned that every time I disturb
something there is risk involved.
Is there anybody in the Seattle area
(northern suburbs) with a known good cable?
If I can eliminate the cable as a possibility
then there is only the DVI connector, as the
rest of it seems to function normally.
-Mike
On Mon, Nov 18, 2024 at 7:10 AM Royce Taft
<[email protected]
<mailto:[email protected]>> wrote:
When I had this issue, it turns out I
hadn’t snapped the connector in fully on
the underside of my M100. I would
disconnect it and ensure no pins became
bent and flattened out. If the pins look
good, carefully replace the connector and
snap it firmly into place.
When making my cable, to figure out the
location of pin 1 on the M100 and the
DVI, I think I used a multimeter and the
pin outs in the various manuals to look
for ground pins which gave some insight
into the orientation of the connectors.
Seeing “please wait” followed by a
Microsoft copyright is a very good sign
that your boot disk was successfully read.
Royce
Sent from my iPhone
> On Nov 17, 2024, at 21:20, Michael
Brutman <[email protected]
<mailto:[email protected]>> wrote:
>
>
> Ok, here is the part I hate ...
getting things put together and then not
having it work.
>
> I'm using Greg's cable kit with a Tandy
102. I have the twist adapter on the 102
side, red stripe oriented as in the
pictures on the Wiki. (The red stripe
closer to the 'S' of "System bus".) That
goes into the IDE ribbon cable, which is
connected to the DVI also using the
orientation in the pictures from the Wiki.
>
> I used Teledisk to create the disk
image. I powered on the 102 first, as
per the DVI user manual. When I power on
the DVI I get the "Please wait!" message,
and then I get the Microsoft copyright
message. All of this is good so far.
>
> Where things fail is when I try to load
disk BASIC onto the 102. The
instructions say to use the Reset button
or to power the machine on and off.
Neither has any effect, and I've tried it
with two different 102s.
>
> What am I missing here?
>
