Ricoh FW780 Service Manual - Page 65
Fusing Temperature Control, Fusing Circuit Operation
View all Ricoh FW780 manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 65 highlights
8.3 FUSING TEMPERATURE CONTROL 8.3.1 Fusing Circuit Operation Rev. 5/95 The fusing lamp is powered by the ac drive board and controlled by the main board. The ac drive board receives direct wall voltage ac power (not stepped down) at T201 and T202. It also receives +24 volts at CN202-1. The ac power is applied to the drive circuit, the fusing lamp, and the triac (TRC201). The dc power drives PTC201 and RA201. To turn on the fusing lamp, the main board drops CN106-B14 to LOW. This activates the photocoupler (PTC201) which in turn energizes the drive circuit. The drive circuit turns on the triac to complete the lamp circuit, thus turning on the lamp. RA201 guards against a failure of the +24 volt power supply. When +24 volts is applied at CN202-1 and CN106-B15 drops to LOW, RA201 is energized and its ac contacts stay open. If the +24 volts power from CN 106-A2 stops, the ac contacts of RA201 close, stopping the drive circuit and turning off the fusing lamp. A163 2-29 SM