Older 67 card readers and 65 card readers

[teenix]

I haven't had a need to adjust a motor speed yet. The 97 service manual seems to suggest increasing resistance will speed up the motor but doesn't specifically say so.

You could remove the resistor and measure it, then with a 10K multiturn trimpot, set its resistance to match, then fit the trimpot to the sense board and adjust the speed as required. Then if you want to, find a 1% or better precision 1/4 W resistor to match the trimpot setting (or as close as possible) and fit it.

The sense amp has a constant voltage source and outputs around 2V to the motor.

See my Classic Notes pages 32.

Ohms law will work with a constant current source feeding a resistor giving the required voltage drop, as long as the source voltage is sufficient and the current source can handle the current.

cheers

Tony