Sharp CE-122 printer motor running too fast?

[Dave Britten]

(09-18-2022 08:42 PM)Jeff_Birt Wrote:  Bad capacitors are not going to increase voltage. The wall wart is for charging not for running. Charge the pack up and then remove the charger. If you keep it plugged in all the time it will boil the battery pack dry. The only charge control on these things is the time you have the charger plugged in. This is true for most rechargeable stuff of this era.

Yup, I couldn't find any electrolytic caps in the schematic for the printer control circuitry anyway, so it kind of rules that out! The wall wart is wired basically in parallel with the battery, and I was getting the same results running from the (charged) battery, or with the printer plugged in too. I probably need to do some deeper disassembly of the printer mechanism and see if anything looks amiss. Not sure what exactly is generating the timing signals to the PCU. I don't think it's any kind of optical encoder, but I could be wrong.