Is this video issue the system, or something else?

[A Black Falcon]

So, some years ago I got a TI99/4A.  I did a thread about it.  A while later, however, I stupidly broke it by spilling water on it while it was running.    The water got on my TI99 and Odyssey 2, but the O2 still works mostly fine (probably helped by its non-porous keyboard), while the TI99 had some crazy stuff display on the screen then died.  I tried to let it dry out and such but it didn't help, it was dead.

 

After waiting a while, earlier this year I finally decided I wanted a working TI99 again.  However, my first attempt did not go great on that front -- it did get me some interesting games and accessories, but the system itself has a bad chip (probably that RAM chip failure issue?) and keyboard.  You can't boot games because a lot of keys don't work, and it has major display problems.  It was listed as "untested" which I was skeptical about of course, but the other stuff with it convinced me to get it anyway.  So, I now have two broken TI99s.

 

... Following this I did some highly unadvised things which broke that second console further.  Let's just say that now neither of those systems or power supplies work at all. ... yes, I tried the power supply from the water-damaged console on the second system and such. It seems to have broken it too.  Whoops... I wouldn't have tried it if the thing worked properly, but it didn't wand I was curious, so... yeah, that was a mistake.  Maybe there is someone who could fix this stuff but I definitely cannot.  (Both systems and their power supplies are now in the basement, taking up space.  I don't want to throw them away though...)

 

 

Anyway, none of that is the point here, I have a question I'd appreciate help with.  So, a few months ago I tried again, and got a tested and working TI99/4A.  And it works, and even has a fully working keyboard!  The graphics display correctly as well.  Neither of my previous ones had a fully working keyboard, even that first one often had some of the keys not respond sometimes.    That's quite nice.  However, there is an issue -- so, I have the RFU that came with this system, and also a composite AV cable I had previously bought.  (Note: this is a mono AV cable, yellow and white to the TI DIN plug.)   And the composite cable works... with some games.  With others, though, the screen goes white after about a second and stops functioning.  The system is fine,though -- if I turn it off and on it runs normally, unless you have one of those games in and watch them fail to run again.  Some games just don't work on AV. However, those same games work fine on the RFU... except of course the image quality isn't as good.  This issue is consistent -- with some games this happens every single time, while with others it never does and they can be played normally on composite.

 

So, is this a problem with the computer, or not?   I don't remember having this issue on my first TI99/4A, but it's been long enough that I don't remember for sure.  I have done some searching and haven't found anything about this problem.  I'm thinking about finally adding to my little TI99 collection by getting a tape drive and maybe the nano-PEB or something, but before I go any farther with that I definitely want to figure out this display issue, I'd much rather use composite than RF if I can.

Edited October 26, 2019 by A Black Falcon

[+arcadeshopper]

There should be no difference using composite in fact out should just be clearer than rf. Pretty sure the rf modulator coverts the composite signal to rf.. so if something isn't working in some display modes I'd expect it's the 9918a chip that's gone bad

Sent from my LM-G820 using Tapatalk

[A Black Falcon]

Bah, I figured something was wrong.  If the modulator is converting composite to rf, it's weird that rf works with everything, including the half of the games that crash with the composite av cable.  That's one strange kind of chip failure there.

 

... Why is finding a working TI99 so hard?  I mean, I know I broke my first two worse accidentally, but neither one ever worked correctly -- the first has an iffy keyboard, and the second a really bad keyboard AND serious display (ram chip?) issues.  And now this one works... but only in rf, av is half broken?  Bah.

[+Ksarul]

Your symptoms actually lead me to the cable as the problem, not the console. If ALL games work with the modulator, it is taking the same signals as its input that the composite cable is using. Try a new composite cable. . .you may get a pleasant surprise.

[Opry99er]

I'm going with cable as well.

 

However, if you'd like to try something.....  you likely have working 9918 chips in your other (broken) consoles... and the 9918 is a socketed Chip.  Pull the shell apart on your good machine and swap the 9918 with one from one of your other systems.

 

Also, order another composite cable... I'd  honestly do that first.  

[Ed in SoDak]

Flat screens add a new variable to the video troubleshooting. Sometimes they don't like some signals that the old analog CRT sets would display no problem. Sometimes passing the composite signal through an old VCR makes it more digestible.

-Ed