9800 Overhead Projector
Section 6 – Troubleshooting
6-4
3M 9800 Service Manual
6-2.
How To Check the Overvoltage
Protector Circuit Board (OPC)
The OPC is a voltage sensing circuit that monitors
line voltage and automatically switches transformer
taps to prevent damaging voltage to the lamp.
The OPC is working properly if at initial power-on,
the LED indicator “BLINKS” red then turns green.
1. Open the top cover.
2. Shade the LED lamp on the circuit board with a
piece of white paper.
3. Defeat or by-pass the power switch and stage
cover interlocks.
4. At initial power-on, the LED should flash red
(one quick flash) then illuminate a steady green.
Note
A “Click” should be heard as the relay
switches the transformer tap from the lower
voltage (terminal 4) to higher voltage
(terminal 5). Figure 5-22. Also, the
indicator lamp should dim slightly.
5. If the LED indicator stays red:
a.
Measure the AC line voltage at the
transformer. The voltage should be above the
switch point setting (SPS). See step 6.
b. If the AC line voltage is below the SPS, the
relay could be sticking. Tap the top of the
relay and test again.
c.
If the LED remains red, replace the circuit
board.
6. Verify the jumpers are set to the correct SPS for
the line voltage at the transformer. Figure 6-1.
Switch Point Setting (SPS) Values
Min/Max SPS Value *
Country SPS Setting
100.5-103V
Korea (Japan) + STD
120.5-123V
US + STD
223.5-226V
OUS + STD
234.5-237V
OUS + STD
244.5-247V
OUS + STD
* Multimeter accuracy must be less than .1%.
Jumper Plugs
(Post Shunts)
Switch Point
Settings
KOREA
STD – –
STD –
STD
US
OUS
9800-98I
Circuit Board
Country
Setting
Figure 6-1. OPC Jumper Plugs
Note
Figure 6-1 shows jumper plugs (post shunts)
set for a line voltage of 120v.
7. If the standard switch point settings yield a short
lamp life, then set the STD jumper to STD–
(reduce by 1 volt) or STD–– (reduce by 2 volts)
as needed to lower the SPS value.