by JIM WOODING
Some NEC 8023A printers generate a high pitch tone or squeal when the power switch is on and "idling". It is caused by defective capacitors that were installed in many NEC 8023A's.
The cure is simple for anyone with any soldering experience. Here is what you will need:
2) needle-nose pliers
3)soldering gun and solder
4) 200 pf ceramic capacitor (I used a Sprague Q-Line stock no, QCP-5135-01 rated at 1000 WVDC + /-20% tolerance.)
Follow these steps carefully:
1. Remove cover (covering ribbon cartridge and dip switches).
2. Remove two (2) screw (see Figure A).
3. Turn printer over, bottom-side up, platen knob facing you.
4. Remove snap-out bottom panel (covering large printed circuit board).
5. Remove only the screws (total 4) located at the corners of the printed circuit board. CAUTION: DO NOT REMOVE THE REMAINING THREE SCREWS!
6. Pull out the end of the printed circuit board nearest you (and farthest from the stepping motor) enough to identify capacitor "C2" (about 1 inch). (see Figure B) This capacitor is marke on the board so you should find it easily. Holding printer bottom-up and the stepping motor away from you, C2 will be at the extreme right of the printed circuit board, directly behind similar capacitor. Heat up the leads with your solder-gun, remove the defective capacitor, install the newly-purchased capacitor and re-solder the connections. Assemble in reverse order, plug in, and enjoy the peace and quiet of your NEW NEC!