Which resistance controls the card reader speed on a HP-97

[brickviking]

(11-07-2017 12:04 AM)Bouw Wrote:  Hi Francois,

What a coincidence! I also finished restoration of my HP-97 this weekend and I also could not get the card reader to work. The exact same problem as you describe: card runs through smoothly but always results in "Error". I removed resistor R1 and soldered wires so I could test resistor values outside the calculator. Unfortunately, it made no difference at all. The original resistor was 4.33K and I tried many values between 3K an 9K. The higher the value, the faster the card goes through. But the error was always there. ...

Kees.

I was thinking (if you can find such a thing) you could use one of those variable resistors that you turn with a little screwdriver, I think they have about ten turns to go from bottom to top of range. Stick that in series with a 3.3kohm resistor, and see whether you have any further luck. You could conceivably stick the variable resistor in parallel with a fixed resistor (say 8.2kohm) and combine the pair with a 3.3kohm series resistor, but that is getting a bit more refined. You may even need a 1% value resistor.

Just my NZ$0.02 worth...

(Post 128)