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Old Yesterday, 10:39 AM   #61
jkb242
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Default Re: Need schematic for Visio LC420

Quote:
Originally Posted by budm View Post
So right now the PS-ON wire, BL-ON wire, and the Dim wire are cut and no longer have any connection to the main board for testing the power supply/inverter combo board, correct?
Checking sound will just have to find out because we do not know at this point what else are bad on the main board.
Please recall this set has a combined inverted power board and this is the second board with the TV same symptom. This board has only two wires leading from the inverter section of the power board, so the lamps are all in parallel.

Hope this helps.
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Old Yesterday, 10:49 AM   #62
budm
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Default Re: Need schematic for Visio LC420

There 1 pair of high Voltage wires.
The lamps are driven out of phase that is why there are two transformers due to the length of the lamps, inside the panel there are ballast cap for each lamp so the lamps are not connected directly in parallel, unless the lamp are EEFL type then they they can be connected directly in parallel and not need for the ballast caps.
"Please recall this set has a combined inverted power board and this is the second board with the TV same symptom" bur we already know that it has problem with the bad main board, right now you are trying to verify if the power supply/inverter and lamps are OK or not.
What is the LCD panel model number?

CCFL, EEFL
http://www.iitk.ac.in/asid06/proceed...rs/TC2_1-I.pdf
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Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/

TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809

Last edited by budm; Yesterday at 10:53 AM..
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Old Today, 08:40 AM   #63
jkb242
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Default Re: Need schematic for Visio LC420

Thanks for the reply and the link to the reference material.

The panel number is LC420.

By disconnecting the main board and applying 5vdc to the control pins on the power connector, have we not eliminated the main board for backlight testing?

So this forced on testing should be viable correct? If so, there must be a bad lamps in the panel. Are the LCD LAMP testers reliable. I was going to try that testing the individual lamps. Can you help me understand what the protection circuit sees if there is a bad lamp? Isnít the lamp gas filled so there is no means for shorting correct? Is the protection circuit on the power board? Again, this is the second board but itís possible that both power boards boards are not defective that I can prove for sure.

Thanks
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