hp 82104A only reads 67/97 cards

[John Garza (3665)]

Yes, I cleaned the head and checked that all the wires were still connected.
UPDATE: I forgot to clean the leaf switches, so I disassembled the unit, and gently ran an alcohol qtip over them for a few passes, then reassembled. Now it doesn't work for any cards! The leaf switches looked perfectly clean and I visually checked their movement (while peering between the card reader frame and their circuit board) with a known good example. Also, I did notice some dry, crumbly, old-dead-drive-roller residue down in the lower circuit card area. Looks too difficult to remove; and since it's rubbery, I assume it's a non-conductor. But could I be wrong?

-John