HP67 repair squelch

[teenix]

(01-15-2020 10:38 AM)murphy9 Wrote:  Help - one of my HP67's has become a squeaky mouse!

Any clues to why I'd get a squelch on an HP67. Power up with new battery and get the squelch/squeak, then error. The motor from the mag strip also powers up for a second.
Could be a sensor on the card reader. I'd be interested to see if anyone has any similar experience before I start taking it apart and probe things.

Many thanks

The HP-67 microcode tests the card status just after switch on. If it "sees" a card in the slot, it will turn on the motor and wait to see if the card is ejected in a certain time. If not, the motor is switched back off and an error is displayed. If so, the motor is switched off and life is cool.

It's possible that...

the nylon ball has foreign matter keeping it held against the card switch,

corrosion anywhere along the circuit path from the switch contact to the CRC chip,

the switch needs adjusting,

something jammed in the card reader slot,

or worst case, the CRC chip has failed.

A word from the once bitten, twice shy. If card reader disassembly is required, this should be undertaken with care. The small parts are experts in the art of disappearing. Also be careful if you really have to adjust the switch contacts, it is easy to overdo it.

Hopefully just a clean up and it will be fine.

cheers

Tony