Sharp IS501 OPIC

The printer is an Olivetti JP10 'Sparkjet'. The encoder unit has the followind moulded int othe plastic cover : 'Encoder GP-1R12 Olivetti Made in Japan' The encoder is fitted to the front of the print mechanism chassis and has as 4 wire cable that plugs into the logic board. To remove the encoder, you unclip a cover over the boss of the encocer wheel and remove the setscrew that hols this to the carriage cable drum spidle. Then undo the 2 larger screws on the front of the encoder and slide it off the spidle. If the cable drumn comes out of the rear bearing there's a real danger the carriage drive cable withl come off and you'll have the 'fun' job of sorting it all out. After rremoving the encoder, it can be dismantled by first peeling off the foam insulator on the rear surface. Then desolder the LED wires (The LED is pushed into a hole in the front cover) from the PCB. Take out the 3 screes, nuts and washers. It then separates into 4 parts -- the front cover (and the LED, whcih can be pushed out), the encoder disk, the rear cover/bearing. and the PCB. I have done this to mine and refitted the rear cover/bearing to the printer chassis just so the carriage cable drum stays in place. The 4 wires to the logic PCB are +5V, ground and 2 output signals which I will bet are the normal quadrature outputs. The encoder disk is bout 30mm in diameter and has 60 slots in it. -tony