HP mx703 Service Manual page 25

5-7 R.G.B. Video Amplifier Abnormal
5-8 Blank EEPROM Trouble-shooting:
Description of functions for models under m703/mx703 series EEPROM DATA AUTO-RELOAD
The function allows plant staff to pre-write and customer service personnel to use blank EEPROM
through the pre-write EEPROM function whenever the CPU is implemented. The method of operation
is as follows:
First, start after m703/mx703 turns to (<&>) KEY. At this point of time, the CPU is capable of detecting the
first 8 DATA of each page that EEPROM contains. When the reading goes to 00H or FFH, the EEPROM
PAGE will turn to blank; instead, the pre-set value is being written into the EEPROM through CPU. Otherwise,
it shall be deemed an effective value and that the pre-write function shall not be activated.
Note: The pre-write operation is only used in the service operation, if the EEPROM becomes faulty, we
need to replace it with a new one, but, to enable the adjustment ( geometry, color temperature, .. etc ) we
have to put in some " factory preset values " so that we can have a good start point, this is what we call "
pre-write " operation.
RGB Video AMP Abnormal
Check
waveform at I501 pin 5, 6
and 7
Yes
Check
I502 pin 1, 2 and 3 collector
voltage (normally about 70V)
& waveform
Yes
Video signal present at the
pin of the CRT R.G.B.
Cathode
Yes
Defective cut-off circuit
(DC restore) I504
Check or replace the
No
signal cable or I501
No Check I901
HP mx703/m703
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