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3) If colors are wrong or missing and white balance cannot be adjusted check:
- Each individual color signal path comparing DC offset and peak to peak signal levels to each other to determine if
there is any single amplifier at fault.
- For shorted diodes on the IC002 outputs.
2. On Screen Display Functions
On Screen Display(OSD)
IC003 is the On Screen Display character and graphic generator. It provides RGB and Fast Blanking data to IC001 for
mixing with the main video channels when required. Outputs voltages are two dimensional, either 0V or 5V. IC003 is
controlled by the Microprocessor via the I2C bus. The sync timings necessary are V sync and H Fly.
Troubleshooting Hints
1) No OSD is displayed, check:
- RGB and Fast Blanking inputs to IC001. If there are no signals then IC003 may be at fault.
- That +5V is supplied to IC003
- V FLB and H FLB signals are at pins 10 and 5 of IC003 respectfully.
- That there is I2C communication to IC003.
3. G2
G2 Amplifier
The G2 reference is provided to IC005 Pin 5 by the IC001 D/A converter. The G2 voltage at the cathode is typically 500v ~
750V.
Troubleshooting Hints
1) If picture is black, check:
- G2 level at the cathode using HV probe.
- Input to G2 amp, Pin 5 of IC005.
- Heater voltage at the cathode.
-+12V, +5V, and G2 voltage coming from D board.
4. Display Data Channel Circuit (DDC)
For DDC2BIC007 is a serial memory device providing Extended Display Identification or EDID data that is read by the
compatible Host Computer on Pin 5. The basic EDID format consist of 128 bytes which are described in the table below.
The 15 Pin VGA connector allocation is also described. The compatible Host Computer provides a V CLK on Pin 7 that is
derived from the V Sync input and is used to set the timing of each data reading cycle. The data is clocked by the input of
IC007 Pin 6. The rear input supports DDC2Bi. The data is passed through the A Board to the Microprocessor on the N
Board via CN311.
Troubleshooting Hints
1. The DDCB circuit should be checked if error DDC messages or erroneous monitor identification data is indicated by
DDC2B the compliant Host Computer. Check that the V CLK and S CLK signals are input to IC007 on Pins 7 and 6. The
Data transition should be visible at Pin 5.
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Table of Contents
Troubleshooting
