Skoal Board Repaired
Added 2021-06-08 06:50:44 +0000 UTCThe topmost Skoal board has now been repaired. Our 9825T now runs on all cylinders, with all of its 64k or RAM and all of its ROM on the Ebenezer board underneath. All set and done, the Skoal board had 4 bad chips: three TTL and again the Intel DRAM controller, so pretty similar to the Ebenezer that had 5 bad ones, including the bad Intel DRAM and a bad ROM.
As luck would have it, I had an original HP-branded version of each of the bad TTL chip. Not that it really matters, but it's nice that these rescued HP parts find their way back into an HP machine.
Repairing the burned ROM on the Ebenezer board was not as straightforward as expected. It had us stumped for a while, and required some artful pin swapping. But at least now we know how to do it, and can make a replacement for any of the ROMs if they were to fail.
It's now on to the keyboard/display. And then we'll have to do the tape board, as we confirmed it was also dead. By the time we are done, we'll have essentially reverse engineered the entire machine!
Marc
