820-3787a no backlight image can be seen liquid damaged.

PCTRONICS

New member
Gday guys I'm using schematics for 820-3332 so hope layout is similar. unit has corrosion on c8513 PP1V5R1V35_S0GPU would this cause no backlight? because I wouldn't think so unless this rail must be complete before backlight shows up. or is it as simple as replace backlight driver? I'm getting 0.560 Diode on L9000. I'm not 100% familiar with this retina model so any help would be great. I'm getting 12v on both sides of the fuse.
 

2informaticos

Administrator
Staff member
820-3787 schematic and boardview available, search better the Internet.

Do you get image, only missing backlight?
 

2informaticos

Administrator
Staff member
Check diode mode to ground at pin 1/J8300 w/ and w/ LCD connected; no power applied, of course.
Also check if F7700 is OK.

Post voltages for Q7706 and U7701, pins 5, 18, 17, 11; LCD connected this time.
Be sure to have continuity from U7701 to R7708/09.
 

PCTRONICS

New member
R7708/09 have cont. R7709 is 16K it should be 150K is this the feedback?

F7700 is fine

J8300 P1 with lcd on is 0.033 Diode mode
J8300 P1 w/o lcd is 1.149 Diode mode

Q7706 P1 -0.060 P2 -0.060 P3 12V P4 12,3V P5 0.060 P6 0.060

Hope this helps
 

2informaticos

Administrator
Staff member
Check R7743/44.
Be sure no short on pins 5 & 18 of U7701, if you need to replace them.
Check first if =PP5V_S0_BKLTCTRL arrives to R7743/44...
 

PCTRONICS

New member
Im getting 5v on both those resistors R7743/4 both 2.5Ohms and both are 0.374 in diode mode
 
Last edited:

JohnB8812

New member
There is nothing wrong with the driver you said you have 0.003 with the screen connected but it 1.1 without. Replace the blown fuse and measure again with a KNOWN GOOD screen
 

2informaticos

Administrator
Staff member
"J8300 P1 with lcd on is 0.033 Diode mode
J8300 P1 w/o lcd is 1.149 Diode mode"
Ooops, I didn't read this full.
You have LCD assemblw problem; video cable, or display itself (more probably).

But confirm again all measurments, because you posted 0V on pins 5 & 18 of U7701 first time and 5V next post.
Always measure voltages with LCD connected.
Please provide accurate information.
 

PCTRONICS

New member
What fuse?. i said i had 12v on both sides. the fuse F7700 is fine unless you are referring to another one. ill try another screen.
 

PCTRONICS

New member
My apologies i measured U7701 with the machine off. the second measurement was with machine on. thanks am getting a screen now. will update in the next hour. both pins 5 and 18 are getting 5v.
 

PCTRONICS

New member
Thanks for your help guys. it was the screen after all. Oh well i guess i better ring the customer and tell him the bad news.
 
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