HP97 The journey begins

[Robert VM]

Success to Tony with the 97 project!! Would be interested to hear how you go about recreating ACT (CRC) functionality with the correct timing.

If I may join the HP97 repair corner...
There's this item that came at a reasonable price but which seemed defective. After opening up, the card reader cable had obviously been put in shifted, shorting adjacent contacts in the connector.
After putting that right the calculator behaved erratically: occasional display of zeroes: "00" or "0.00",
almost no response to the keyboard. Later the printer printed out lines with mostly 'N's a single 'I' and '0's.
Then the idling gear lost some teeth.
To continue the search I disconnected the printer board: no activity at all...
That was some time ago.
I did transplant the 97 ACT into a HP-21 and that seemed to function well.

Just recently, looking through the schematics it became rather obvious why nothing functions when the printer board is disconnected. The oscillator elements for the ACT, that I couldn't find on the logic board, are situated on the printer board!
The interconnects for these elements are somewhat 'powdery white': oxidation?
Haven't yet done the extra cleaning of these contacts...
Does anyone has an idea why these oscillator components were put on the printer board and not near the ACT itself?
Likewise the card reader board and display board have some of the power supply components.