Read?Write HP 67 card reader

[AnnoyedOne]

(10-05-2024 03:53 PM)Geoff Quickfall Wrote:  ...circuit diagram which can be found at his site (PLEASE check it out)

I've looked. It looks like a -Ve voltage (VGG) is being generated for some of chips. Note the polarity of C4 (2.2uF).

The motor (MOT) is driven by the "CRC" chip (U3). VGG also goes to this chip.

I don't see any value for VGG but 3 of the 4 tantalum caps are in that power circuit.

A1