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home>>Tech tips>>Tech tip #3
Marquee Scan Reversal
Those about to ceiling mount their Marquee projector, or who wish to use a priorly ceiling-mounted Marquee on the floor or table, may find it necessary to reverse the horizontal or vertical scan, or both. This is easily done by unplugging the yoke connectors, giving the yoke connector a half a turn, and plugging the connector back in:
Horizontal Scan Reversal
With the power cord unplugged, remove the projectors' metal lens cover panel by pulling the front of the panel up and out of its' snaps. This will reveal two phillips screws that are securing the larger main metal cover; loosen the screws and pull the cover rearward and up to remove it. The Horizontal Deflection Module, mounted in a vertical metal sleeve between the green and blue tubes (see PIC 1), provides pulses upwards of 1500 volts to drive the tube beams across the phosphor on each tube face. The red/white/blue wires carry these pulses to the sweep yoke, the gray bell-shaped device with yellow tape wrapped around it, (also visible in PIC 1) mounted frontmost on each tube neck. The yoke contains sets of copper windings that generate magnetism to move the electron beam across the tube face. The yokes on newer Marquees (M8110, M8500, M9500) use couplers that place the connection outside of the metal sleeve holding the HDM; this makes for fast access for users such as rental companies who need to reconfigure their units frequently; older M8000s and M9000s have the yoke sockets mounted onto the board and are more difficult to access, but the idea is the same. The yoke connector in PIC 1 is set for floor/table mode; you can tell by observing that the red wire faces another red wire and blue faces blue. To reverse H. Sweep for ceiling mode, merely uncouple each yoke connection by pulling the yoke plug away from the pins (see PIC 2), give it a half a turn (see PIC 3), blue wires now face red wires giving opposite polarity from before, and plug the coupler together again (see PICs 4 & 5). Repeat this procedure for all three yokes. Be sure to reconnect the plugs where they came from, the connections are tube-specific because static or full-frame convergence is delivered through the sweep connections as a dc offset to the yoke pulses.

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Vertical Scan Reversal
Locate the vertical amplifier module on the rear heat sink, it is behind the blue CRT neck board cover (see PIC 6). The yoke plugs have yellow/green wire pairs and are plugged onto pins on the board, couplers are not employed. The vertical yoke plugs are more easily accessed if the rear heat sink is flapped open (see PIC 7). To reverse vertical sweep, merely pull up on the yoke plug (see PIC 8), give it half a turn (see PIC 9), and press it back down onto the pins (see PIC 10). Return each plug to the correct pins to ensure correct static convergence function. Following scan reversal, a full setup of geometry and convergence will be required, as well as zone focus and zone stig in the Service menu.

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