My plan is to de-solder the 75LS254 , evaluate the chip, repair the traces, then reinsert a known good chip.

I've read a comment about this board that suggests something curious. Sounds like there are versions that require the parity chips and versions that don't require the parity chips.

Any idea if the difference is motherboard layout, different chipset revision, or is it just a BIOS thing?

seeing the state of the pins on the LS245 I would not recommend bothering with it at all - chances are corrosion is creeping inside it
just snip it off the board (thus making desoldering easier and less stress on the already stressed pcb area) , install a socket and a new chip and see what happens

keropi wrote on 2025-06-26, 19:31:

seeing the state of the pins on the LS245 I would not recommend bothering with it at all - chances are corrosion is creeping inside it
just snip it off the board (thus making desoldering easier and less stress on the already stressed pcb area) , install a socket and a new chip and see what happens

That's good advice. But I just got a Hakko FR-301 for my birthday with a 0.6 mm head so I had to try. Miracle device. Cleared all 20 holes in less than a minute. Just sick. But the corroded pins were not coming out so I had to cut them and give them a twist to get them out. So you were right in the end. The chip wasn't going to make it

5 Trace Breaks---

typical acid damage...
use a fiberglass pen to clean the affected area - it will reveal all copper breaks easily - the soldermask on the area needs to go so you get access to the copper to perform the repairs

Took me a while to find that fiberglass pencil. Turned out I put it with my soldering stuff. Maybe I should have looked there first! I cleaned things up best I could

Only took a minute to find my donor wire from the sacrificed floppy drive

I considered making a video of the soldering, but it would have been more slapstick humor that instructive. There are now another pair of 3mm length tiny copper wires somewhere in my carpet. Still I was pretty pleased with how it turned out. I know it works best if you do your runs "via to via", but it was awkward to do that here so I just did short runs and counted on the socket to keep things in place.

Next came the socket. I accidentally inserted a 16 pin socket at first. I had soldered two pins before I realized it. How did I miss that? Fortunately it came out easily. Once I got the correct socket, I had a hard time getting the corroded sockets to take the solder. Probably didn't clean it out well enough. Singed the board a bit, but it seemed to take well enough to risk applying some power. I checked for shorts first. Easy to remember to do that ever since that time the tantalums blew up in my face.

Next thing you know, Huzzah!

Next up-- New battery and MR BIOS!

There were too many repaired traces by the battery ground so I took it in a different direction. I can never remember the correct way to do the diode. Let me know if I messed it up.