Let's see the rest of that dvi cable.
If you bought a cable from arcadeshopper, you should not need to do that
even-to-odd crossing.
You would need to twist the wires only if the rest of the cable was all
standard IDC connectors.
The cables I made for arcadeshopper all include a part that does the
twist. (Unless maybe he's sold all of those and now selling something
else.) But the best version of cable comes in 3 pieces and one of the
pieces is a male-to-male plug that has the twist inside, so that all the
rest of the cables can be standard, so you could replace the cable if it
wears out, or add an extension for more length, etc, without needing to
do anything funny.
Another confusing element is, the tandy manuals number the pins
incorrectly on the 102/200 end. What they call pin 1 in the tandy manual
is actually pin 2 of the connector. So what the 200 service manual calls
pin 1 does not go to the triangle mark on the connector. But the DVI
manual does number the pins correctly.
The end result though is, Take the entire cable including all parts and
adapters that you might be using (those individual wires in this pic are
new to me, is it something you made up yourself?), and pin 1 at the DVI
end needs to go to pin 2 at the 200 end, and when I say pin 2 I mean the
real pin 2 according to the standard way to number the pins on that
connector, not what the 200 service manual call pin 2.
Here are several ways to make a cable
http://tandy.wiki/Disk/Video_Interface:_Cable
The simplest for a 200 is to get a male-male gender changer pin header
like at the bottom of the page, or better yet, take 2 male boxed headers
and solder them back to back with the polarity notches on opposite
sides. This produces the same result as twisting the wires, even though
physically it's just passing straight through, but 1 goes to 2, 3 goes
to 4, etc.
Then just use an ordinary 40 pin cable with female connectors on both
ends, installed normally, no funny business, like a standard IDE or gpio
cable or something (as long as it has all 40 pins, many ide cables have
one pin missing and/or one wire cut).
If you follow the github links to build a cable yourself, there are bom
links there to the actual parts on digikey.
If you have an arcadeshopper 3-piece cable, just plug the long cable
into the dvi, then plug the male-male adapter on the free end, then plug
that into the 200. Don't use the 3rd piece with the DIP-40.
No twisted wires like in this pic. The male-male adapter does that already.
--
bkw
On 9/25/24 19:46, Tom Blum wrote:
Hello,
I'm looking for any thoughts about potential faults that could explain
the following.
* T200 (that has been thoroughly inspected inside/output) powers-up and
is functional when not connected to DVI. Also powers-up and functions
with system interface cable attached to T200 as long as cable is not
connected to DVI. No optional ROMS are installed. Available memory at
power-up is 19K+
* Disk/Video Interface operates to spec when not connected to T200. DVI
boot sequence is nominal. Successfully loads ver 1.00.00.200 of disk
basic and displays confirmation of such on composite monitor.
Successfully boots with system interface cable attached to DVI and T200
_as long as T200 is not powered on._
* When T200 is connected via system bus to DVI (_with DVI powered off_),
T200 does not successfully power on. When the T200 power button is
pressed, the LCD screen goes solidly dark with no apparent other
functionality. It seems frozen. When DVI is subsequently powered on,
while T200 remains in frozen state, DVI sometimes succeeds and sometimes
fails to load software from the DVI disk. T200 can only be recovered by
cycling memory power switch on the underside of the T200 off-on.
A picture of the connector is shown below. It has been connected to the
T200 and DVI per illustrations from Arcade Shopper. As a cross-check,
I've ensured that pins on the connectors are intact and fully-inserted.
Intuition suggests that the issue resides with the T200 system bus, the
T200<->DVI cable and/or the "PPI" circuit of the DVI. Ironically, the
service manual for the DVI refers users to the T200 service manual if
there are issues with loading disk basic onto the T200. The T200
service manual/troubleshooting section does not address this problem.
Any thoughts on where to start? I do have a spare, working T200
motherboard. Swapping that in might help rule out issues on the T200 side.
Thanks, Tom
--
bkw
