HP-65 more on the card reader

[teenix]

(01-31-2019 12:30 PM)albertofenini Wrote:  Hi Tony,
look at this picture,
the bottom (usually curved) should be common to all
the inner or shorter (the middle one) is the first activated since is the first encountered by the card and I believe turns on the motor
If this is true, then the upper one (A in my picture) should the one the is triggered by the upper left corner of the card.
What are B and C doing ?
And, how can I check if a recordable card is treated like a record protected ?
Thanks for help !

I'm pretty sure the four switches are, a motor inhibit switch, a motor on/off switch, read/write head activate and write inhibit.
Not sure what the motor inhibit switch does but probably for jammed cards or something.
The 4 switches should go to the CRC chip and WE comes from the ARC chip direct to the CRC chip.

It looks, as you say, the 5th contact is just a common connection for the 4 switches to (probably) ground.

Looking at the switch lengths should give the clue as to the sequence of operation.

My guess,

the switch marked "motor" is motor on/off, C is motor inhibit, or the other way around,

A and B would be the head activate and write inhibit. One of these will activate last if the card corner is cut. Probably A as it is near the card outer edge.

Assuming A is the write protect switch, then if it is not making contact at all, the CRC chip might assume that the card is write protected.

Assuming the common contact is ground, maybe you can connect an ohmmeter to ground and the control pins (one at a time) on the CRC, then you should be able to see what switch is operating if you carefully slide a card in with no power applied.

cheers

Tony