TI99/4A replacement rom

[repetto74]

Hi Guys,

 

I have troubleshooted a faulty PAL TI99/4A and luckily I had another working machine to test by swapping the IC's. The faulty TI99/4A gives a black screen with a continuous pitch sound.

It appeared that one of the two ROM chips is faulty, when swapping this rom into the working machine I have exactly the same problem.

 

The ROM is the one sitting on the left of the two scratchpad Ram IC's and labelled :

8228

C71077

 

My question is to know the best action to replace this ROM. Is it affordable buying one or can it be replaced with any compatible Eprom ? I do have a programmer so in case this can be done I would like to have a guideline on how to proceed :-)

 

Many thanks!

Rick