Is there an FCC number on the back side of the card?

The only numbers are: 8612K

Since the error pattern is uniform, either a video memory chip or the character ROM has gone bad.

Okay, I made some progress. After your suggestion I checked around the RAM and found a burned capacitor and a broken trace. I fixed them and these are the results. Some of the characters are missing and appear in the wrong places. Where should I look next? I also included a correct image with a working card.

Miphee wrote:

Okay, I made some progress. After your suggestion I checked around the RAM and found a burned capacitor and a broken trace. I fixed them and these are the results. Some of the characters are missing and appear in the wrong places. Where should I look next? I also included a correct image with a working card.

I'm not digging that second shorter trace next to it. Can't tell the true nature of the damage from the fuzzy photo.

That trace is okay. I keep looking at the board and checking continuity but no more broken traces.

A few more pictures.

Unfortunately I'm very stuck.
I measured what I could in-circuit. Either I missed something or one of the ICs are bad.
What does the one in the socket (UM2301) do? No datasheet or any info. My other suspect is the 74LS374 above the socketed one, it is connected via the broken trace to a memory chip. I tried in another motherboard, same missing characters.

According to the sticker in the bottom left corner of the card, it is manufactured by DTK. The PII-133 is likely the model number.

The closest match on TH99 is the PII-134

http://www.uncreativelabs.de/th99/v/C-D/50173.htm

Thank you all, I give up.
The font rom works fine on another card so it must be one of the logic ICs. I suck at soldering those so I won't risk further damage unless I know exactly which IC I'm supposed to replace. Too bad, it is a nice card.