[jaystainbrook]

Hi everybody. I picked up a TI-99/4A at a garage sale and was looking forward to playing around with it. Unfortunately, it looks as though it has a few problems. the TI splash screen comes up but the text is garbled.

Ive attached a photo of the screen. Any ideas? not afraid to break out the soldering iron.

   

[sjt99]

Hi everybody. I picked up a TI-99/4A at a garage sale and was looking forward to playing around with it. Unfortunately, it looks as though it has a few problems. the TI splash screen comes up but the text is garbled.

Ive attached a photo of the screen. Any ideas? not afraid to break out the soldering iron.

Seems to be the video processor.
I actually haven't had one apart (TI console) in many years, I believe the video ic is in a socket.
There is a upgrade out there that will replace the video chip and give you
better video as well.

See next messages for additional info on this
Try pulling the chip and putting it back into the chip socket.

[ksarul]

Classic symptom of a bad video RAM chip. These are soldered to the main board, so if you are not handy with a soldering iron, you might be better off trying to get another console. The video RAM chips are relatively cheap (about $1 a pop), but there are 8 of them in there, all in a long row on the left half of the motherboard (they are TMS4116s). One of them is dead, so you have a bit stuck and that is what's garbling your display data. This is actually a relatively common problem, as I've fielded questions from about half a dozen folks this year on it.

[sjt99]

Classic symptom of a bad video RAM chip. These are soldered to the main board, so if you are not handy with a soldering iron, you might be better off trying to get another console. The video RAM chips are relatively cheap (about $1 a pop), but there are 8 of them in there, all in a long row on the left half of the motherboard (they are TMS4116s). One of them is dead, so you have a bit stuck and that is what's garbling your display data. This is actually a relatively common problem, as I've fielded questions from about half a dozen folks this year on it.

I should have told him to look at the ram, as well.
It may not work but he can try and place a known good ram chip over the originals one at a time and see if it clears up.
It's something I've done on arcade boards, for a quick id

Just bend the pins of the dram slightly in and place over the chip on the board, hold it in place (pressure down) on it.
Make sure all pins are touching the board chip.
Turn on the console and look at the screen and note any change.
It is possible for more than one chip to be bad. If it changes but doesn't completely clear up, try it on another chip and see if there are any more changes.

[jaystainbrook]

Thanks guys. I think I'm going to give the video ram swap a shot. Playing with the console was the whole point of picking up this beast in the first place. This also explains why anything I put into BASIC gives an "incorrect statement" error (took a while to decipher that) since according to what I've read on the web BASIC uses the video ram.

[jaystainbrook]

Well it was indeed the video ram. I used sjt99's trick and the video came right up like it's supposed to.

Here's the chip piggybacked:
   

And the screen looking better:
   

Here's the permanent repair seated in a socket the way nature intended:
   

And BASIC works now too!
   

[sjt99]

Well it was indeed the video ram. I used sjt99's trick and the video came right up like it's supposed to.

Here's the chip piggybacked:


And the screen looking better:


Here's the permanent repair seated in a socket the way nature intended:


And BASIC works now too!

Nice work.
Thanks for uploading the before and after photos. It should be a help to others.