Crossed video wire resets console?!

ramidavis · August 17, 2015

Hey all, as i stated in my first pot on this forum i picked up a ti99/4a console from a discount center recently, have been toying around with it.

Everything seems to be perfect working condition, but the other day i was having a little coding session, when i bumped the video cord, and my console reset (Using the term reset loosely here. Hung at a black screen with loud constant beep, actually)...

The video cord i am using does not appear to be a official TI product.
It has the same round 5 pin connector, but ends in blue red yellow and black leads.
This was sold with the unit when i got it. I had discovered that the black was audio and the blue was video. The red and yellow did not seem to do anything so i just left hanging unplugged.
When i moved the video cord, i appearently crossed the red and yellow leads together.
For now, i have resorted to plugging the "unused" red and yellow leads into unused ports on my video selector.

I can confirm that crossing the red and yellow wires will cause the system to hang, but sometimes the system actually does do a real reset back the main title screen (color bars and TI logo).
To get a real reset, the wires have to just barely come into contact then seperate, almost immediatly. If left in contact any length of time, the system just hangs with a black screen, and some times loud beep sound.

At either rate, if anyone out there has a video cord like the one above and is using it on the TI, beware.
On a typical 3 lead rca wire, there would be a video, and l/r audio.
If the blue is the video (and it seems to be), and the black is an audio line, then either the red or yellow should be another audio line.
That still leaves an extra wire... For what?
I have no idea was this wire was originally supposed to be for, but it seems to work ok on my TI, so its good enough for me. Just have to avoid crossing those wires.
Prehaps this wire is from the commodore/amiga days?

Shift838 · August 18, 2015

I had one of these 20+ years ago and noticed a similar issue. I remember that mine was made for multiple computers, TI-99/4a and Commodore come to mind and was NEW i purchased from a computer store in town.

I ended up just making my own specific for the TI to resolve the reset.

It was something quirky with the cable.

sparkdrummer · August 18, 2015

There is 12 volts on one of the pins on the the din jack. It was used to supply power to the video modulator that was standard equipment with the ti. I'm betting the center pin on one of the unused plugs touched the outer connectors (ground) and caused the glitch. I suggest insulating the unused connectors if you continue to us this cable.