HP 82143A / HP 82162A foto coupler (encoder) - substitute

[grsbanks]

(01-29-2017 09:15 AM)AndiGer Wrote:  UPDATE
The line feed is always done after switching the printer on.
Because after alpha printing I have to switch it off to come back to home position there is always a line feed.
I switched the Honeywell to the working printer as well. Does not work inside that one. Looks like double width printing but with gaps middle of the characters. Print head gets stuck in the left hand wall.

At this point what you really need is an oscilloscope to look at the characteristics of the wave form coming out of the phototransistor and the op-amp. (amplitude, duty cycle etc.)

If you can compare both devices it should be possible to tweak the values of some of the nearby components, but let's also not forget that the original photocoupler's characteristics will have been thought about and chosen for some specific reason.