I recently procured a dusty classic Model B from a local loft. After getting it safely recapped, and plugging in an MMC ROM (as it was tape only), I turned it on today and got very confused:
The bottom line is me typing ABCDE..XYZ. The machine works perfectly in every other mode but 7, oh the irony! It looks like bit 5 of the character display is always set to 0, so P (ASCII 80) becomes @ (ASCII 64) and so on. This gets very confusing very quickly but the machine does run. Does anyone have any idea what's going on here? Do I likely need to replace the Teletext chip? Is that even possible.

Thanks as always!