HP 19C carriage return

[Katie Wasserman]

(09-09-2014 03:53 PM)Geoff Quickfall Wrote:  Hello Katie,

I will check the current and voltage again. The problem is the motor momentum and run time is too fast and long. As though the parked signal is not being accepted. The motor correctly de-powers but the momentum from the RPMs carries it through the parked position and right back into the run mode.

Is there a feedback current that brakes the motor once it starts its return? Is paper thickness part of the braking concept using friction?

Looking at Tony's hand drawn schematics it looks like there is a braking circuit, similar to the one described in the HP-97 service manual. Pin 10 on the PIK chip drives a single NPN transistor that shorts out the motor winding.