2-16 Phaser 8400/8500/8550 Color PrinterDrum Assembly And Transfix SystemThe drum assembly and transfix system form the key portion of the printer whereimaging takes place. The drum assembly and transfix system are separate, yetinterrelated. This section discusses the drum assembly. The next section providesmore detail on the transfix system.In operation, the image to be printed on paper is first “printed” on the rapidly rotatingdrum. The paper preheater heats a sheet of paper or transparency film to prepare it forthe image transfer process. The heated paper is then passed between the drum (nowrotating much more slowly) and the transfix roller. The pressure between the drumand the transfix roller transfers the image to the sheet of paper. An encoder disk andsensor on the left end of the drum monitors the drum’s speed and position.The drum heater heats the surface of the drum to about 60 o C (140o F) for imaging.The drum heater does not rotate. The heater is inside the drum, and is controlled bythe drum heater relay board. The drum heater consists of two resistive heater coils thatoperate in series for 220 V and in parallel for 110 V operation. The drum heater relayboard controls the series/parallel operation. A temperature sensor in contact with thedrum surface monitors the drum temperature. The main board interprets the sensor’ssignal and turns on the drum heater and drum fan to heat the drum, or turns on thedrum fan alone to cool the drum.Paper PreheaterTransfix RollerPaper PathDrumDrum Heater s8500-019
