NJRoadfan said:

According to the Apple IIgs Technical Reference, the character ROM is stored in the Mega II chip, not the main ROM. The Mega II is also responsible for generating text screens on the IIgs.

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That what I read on some webpages searching for this info.

I'm hoping that my test will say if some address lines going to it might be rotted and need to be rerouted. From the looks of it, the low 4 bit addresses are OK, the high 4 bits might be bad. Time to pull out the multimeter!