Greetings, OCAU retro crowd! I come to you today to get assistance as to where to start looking with regards to a Commodore 128D that's decided it doesn't want to display text correctly. I'll lead with a picture, then explain a bit more following. Essentially, what appears to be happening is that bit 2 of the character ID is getting "stuck", for lack of a better term. Not completely stuck, since "COUMOFORG" is clearly trying to the first M, the D and the last E, but it's not succeeding. Those quotation marks are the result of a space with bit 2 active. The same, as with all the following, persist in both C128 and C64 modes (so it has to be something common to both). Prior to it showing this, it hadn't been used in quite some time. I don't know exactly how long, but 20 years is not outside the realm of possibility. When it was initially fired up, bit 2 was actually stuck off - the sequence "0123456789" would read as "0101454589" reliably. We (my brother and I) pulled it down, cleaned it out (dust aplenty) and tried switching the CIA chips to see if it did something. And oh boy did it do something! Since the screen started to look like what you see there, and some of the keys now weren't working (arrow keys, enter, and some others I don't recall specifically), we figured it was a dud chip. So we switched them back to verify and, while the keys worked again, the screen was now stuck like that. What makes it even more weird is that we switched the CIAs again (I'm not sure why) and the keys now worked while the display stayed corrupted. It's not quite as straight-forward as it looks, though (not that it looks straight forward). For starters, the screen will constantly adjust itself. Some of the errors come and go, and over time it actually appears to be "fixing" itself, but it's never perfect. It also gets "better" when the system is under load, such as reading from an SD card adaptor. Copying the character set to RAM and then displaying that instead works just fine, so it stands to reason the character ROM itself isn't the issue. Further to this, if you use a partial graphics mode than a few lines under where the graphics portion ends will be fine, for example: And the last peculiarity (which I unfortunately don't have photos of) is when filling the screen with characters. If you fill the screen with characters that don't normally contain bit 2 active like "A" than it shows as you'd expect with some of the characters on the left trying to look like a "C" instead, with more failing if you add some actual Cs anywhere on the screen. But if you fill them with a bit 2 character like C than the screen is perfectly stable while the last 8 characters on the bottom line are coloured: black, white, black, red, black, cyan, red, white, in that order every time (or colours 1, 2, 1, 3, 1, 4, 3, 2). Since the CIA swap failure (we checked with some donor CIAs from a C64 to verify they weren't the problem), the only thing we've done is re-seat every socketed chip and give the whole thing a going over with a toothbrush and isopropyl. This has apparently made it better (so much so that C64 supposedly almost looked normal) but it still persists. As it stands the only plan is to try that again, this time with an electric toothbrush, and clean up the legs on the two chips which appeared a little dulled (one was for the 80-column display, but I don't recall what the other one was). Unfortunately my brother is the "primary" on this one. It's at his place and he's got a Bachelor of Physics, so it's difficult to argue with him given my background is mostly from work experience on ECUs. So I can say he's reluctant to bath it in water of any kind to clean it thoroughly, nor is he keen on the idea of re-capping the whole thing (the two steps that show up frequently when I search for retro PCB restoration). But he's open to ideas and I'm hoping you guys might have some. PS We're also having trouble with the floppy drive. If it's plugged in than the drive motor spins and the light stays on, but that's where it stops - literally, as it locks up the system. We've tried switching out the only two socketed chips with a donor 1571 but it didn't help.