JVC 250 service manual Video Amplifier PCB, Scan Reversal PCB - Remove and Replace

Chapter 5---Electronics

7.Power ON the projector and allow it to stabilize for a minimum of 15 minutes. It is recommended that the projector be operating for a least one hour before performing shading adjustments.

8.When changing jumpers for floor or ceiling screen projection, Centering, Convergence and Shading must be rechecked.

Scan Reversal PCB - Remove and Replace

The Scan Reversal PCB is located on the front side of the Electronic Module (see Figure 5-2).

Tools Needed

#1 Pozi-drive Phillips-head screwdriver

Parts Needed

Scan Reversal PCB p/n 102585

To remove the Scan Reversal PCB:

1.Power off the projector by IR Remote or PC, and allow the cooling fans to run until they shut off automatically.

2.Turn the AC Circuit Breaker to the OFF position and unplug the AC Power Cord.

3.Remove the projector rear cover.

4.Disconnect seven connectors (seeFigure 5-25):J52, J54, J64, J65, J66, J50 (or J50A), and J100 (or J101). To remove, push in slightly, squeeze the tabs, and then pull connector out.

5.Move all cables out of the way.

6.Remove the four Pozi-drive screws (see Figure 5-25) and lift the board off the Electronics Module.

7.Reinstall in the reverse order from above.

5.9Video Amplifier PCB

Video Amplifier PCB - Main Functions

!Amplification of video signals and driving the cathode of all three CRTs

!Sensing the cathode beam current for all three CRTs

!G1 regulator for all three CRTs

!Blanking drive section

!Phosphor protection for all three CRTs

!G2 regulator and adjustment of black level (screen) for all CRTs

!DC restoration for the video signals

!CRT interface for focus, heater voltage and ARC ground

Model 250 Service Manual 5-43