One weakness of the Sharp CE-150 printer unit is the non-removal Ni-Cd batteries. After 20 – 30 years now since their release they begin to leak. The battery acid (potassium hydroxide, a base, actually) will sooner or later destroy the circuit board and anything else inside the printer. At that point the batteries are usually already dead and connecting a Sharp PC leads to “Error 78”, “Error 80”, or “Check 6″…
In case of such damages I usually use vinegar to clean up the case. Just put the case and any corroded parts (even if they are metallic) into a vinegar-water-mixture for a few minutes.
In case of circuit boards I’m using simple tap water and a brush to carefully remove the corrosion. Most parts on such a board can handle such a treatment. In this case I avoided getting water onto the relays and the ribbon cable. Afterwards drying the board is important, a regular hair dryer (or a temperature controlled hot air gun) will do.
I’ve made a short video tutorial on how to open, check, and if necessary repair a Sharp CE-150 printer unit which is used in combination with Sharp PC-1500 / PC-1500A / PC-1600 pocket computers:
One final remark: the printer will run fine even without the batteries. These batteries were used to provide the 1 – 1.4 A peak current to drive the printer solenoid and motors. The old power supply that was shipped with the CE-150 only provides about 500 mA. You can attach a newer one that is able to provide sufficient current without problems (9 V, negative pole is in the center).