Older 67 card readers and 65 card readers

[James Linder]

Near the top of the card reader control board there are 3 silver cylindrical semiconductor components with axial connectors that have red rings at the tip located near the top of the board, all installed parallel to one another.

These appear to be 3 identical capacitors however they are each marked differently. On the 67 I’m working on now, when looking at the calculator from the backside the center one has 22 uf M which is simple to understand if M is the tolerance rating. The one on the right has 15 K on it, and the one on the left has like a part number on it. Again, Other than the ink markings these 3 components are identical in physical appearance and size.

I’ve been cosmetically restoring HP calculators for years, but I’m a beginner at troubleshooting the individual semiconductor components. I recognize a resister at the very top of the CRC board on the far right, precisely where the later 67 card readers have a capacitor that often needs replacing, but on the older 67 models and the 65’s there is a resistor in that position.

I would tend to assume that the red tips on these silver capacitors are to indicate the anode or more positive end. Does anyone know if all three of these are 22 microfarad capacitors or how to correctly interpret the inked on numbers and letters of each of them?