Posts: 1,162
Threads: 26
Joined: Aug 2005
I agree the problem is most likely to be with the leaf contact -- although it could also be the Card Reader Chip on the logic board (the largest chip on the board). However, if the write protect contact is permanently closed, then the calculator will think all cards are write-enabled, and will not give an error on writing.
I believe HP modified some calculators (maybe only 97s) for in-house use by connecting a toggle switch in parallel with the write protect swtich. When it was closed, the machine would write on 'clipped' cards. This was sometimes used to re-write Program Pac cards, for example. How it seems to work is that the calculator looks at the state of the write protect switch when the card-at-head swtich closes. If the write protect switch is closed at that time, then the machine assumes the card is not clipped, and will write to it.
Anyway, for the 67 we're troubleshooting here, I'd start by cleaning (_carefully_) the leaf contacts and the pads on the keyboard PCB that it touches. If that doesn't help, try _slgihtly_ screwing in the adjusting screw for the write-protect contact, which IIRC, is the one nearest the display end of the machine.