HP-67 1705A01234 [erase other's cards, writes and sometime read back its own cards]

[teenix]

The write protect checking is not activated when reading cards so shouldn't have any effect.

The only way the cards can be erased while reading is if a current is passing though the heads, or the head is magnetized somehow. I can't see any other way. However, you say the cards can be read back sometimes, so maybe not erasing, but not writing properly.

If you released pressure on the card adjustment it may make the card write weaker because the head is not in proper card contact. Try changing it back or increasing the pressure a bit and see what happens.

Make sure WE stays at a LOW level all the time when reading.

cheers

Tony