Phaser 4500/4510 Service Manual 2-29Theory of OperationElectrical24 V interlock This safety switch interrupts 24 VDC from the LVPS to theHVPS/engine logic board and main motor when the top cover is open. Thisswitch operates in series with the rear cover switch. See “Schematic Diagramof Phaser 4500 Power Distribution and Interlocks” on page 2-31, or“Schematic Diagram of Phaser 4510 Power Distribution and Interlocks” onpage 2-32.5 V interlock This safety interrupts 5 VDC power from the LVPS to the LDassembly of the laser assembly when the top cover is open. This interlockworks in series with the laser interlock. See “Schematic Diagram of Phaser4500 Power Distribution and Interlocks” on page 2-31, or “Schematic Diagramof Phaser 4510 Power Distribution and Interlocks” on page 2-32.Rear cover switch This safety switch interrupts 24 VDC from the LVPS to theHVPS/engine logic board and main motor when the rear cover is open. Thisswitch operates in series with the 24 V interlock. See “Schematic Diagram ofPhaser 4500 Power Distribution and Interlocks” on page 2-31, or “SchematicDiagram of Phaser 4510 Power Distribution and Interlocks” on page 2-32.Main fan This vents air inside the printer to prevent an excessive rise in theinside temperature.Sub fan This fan takes outside air into the printer to prevent an excessive risein the inside temperature. This is mounted near the laser assembly in thecenter on the front side.LVPS The low voltage power supply provides 5 V and 3.3 V for logic circuits,5 V for the laser diode, and 24 V for motors and clutches. P4510: The LVPSboard includes the DC-DC converter (described below) as an integral part.HVPS/engine logic board The functions of the HVPS and engine controller arebrought together on a single circuit board. The HVPS provides high AC andDC voltages to the BCR (charging), magnet roller (development), transferroller (transfer), and detack saw (peeling). The engine logic controls theprinting operation according to the information obtained throughcommunications with the image processor and from sensors and switches.Image processor board This receives data from the host computer, performsprinting, and controls the whole printer.Exit motor PWBA This controls the exit motor assembly according to a signalfrom the HVPS/engine logic board.Interlock switch assembly This assembly consists of the following two safetyswitches. See “Schematic Diagram of Phaser 4500 Power Distribution andInterlocks” on page 2-31.Top cover switch P4500: This safety interlock interrupts the INTERLOCK BEFsignal between the LVPS and the HVPS/engine logic board to indicatethat the top cover is open.Laser interlock P4500: This safety switch interrupts 5 VDC from the LVPS tothe LD assembly of the laser assembly when the top cover is open. Thisswitch operates in series with the 5 V interlock.DC-DC converter The DC-DC converter uses 24 V and 3.3 V from the LVPS tosupply 5 V and 3.3 V to the image processor board. By using the 24 V, theDC-DC converter supplies additional power for the optional hard drive andseveral other subcircuits.P4500: The DC-DC converter is on a separate circuit board from the LVPS.P4510: The DC-DC converter is an integral part of the LVPS.
