manumathew.017
Member
I had 8.5V at the boost circuit output, I have changed the backlight driver and wired the missing feedback line. When I connect the feedback wire input fuse is failing, Not sure why. I don't see any short at output
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A1466 No back light
- Thread starter manumathew.017
- Start date
So you get image, only missing backlight?
Post diode mode to ground at both pins of D7701; w/ and w/o LCD connected.
Any history available?
Post diode mode to ground at both pins of D7701; w/ and w/o LCD connected.
Any history available?
manumathew.017
Member
Voltages at diode mode with respect to ground
Without display - 0.610V and 0.417V
With display - 0.607V and 0.416V
Without display - 0.610V and 0.417V
With display - 0.607V and 0.416V
Be sure to connect feedback trace correctly.
And change U7701.
And change U7701.
manumathew.017
Member
Look at the feedback pin and the missing pins, I think its an impossible task to solder the missing line ,
I don't understand what is the problem there.
R/C7704 looks good as their trace to U7701 too.
When feedback is broken (XW7720), this is what you need to do.
R/C7704 looks good as their trace to U7701 too.
When feedback is broken (XW7720), this is what you need to do.
xw7720 fix.jpg
drive.google.com
manumathew.017
Member
I am sorry, I didn’t understand that picture, could you give me bit more information?
Compare it with boardview; then run corresponding wire.
We have posted XW7720 pictures on the forum...
We have posted XW7720 pictures on the forum...
manumathew.017
Member
I have made a connection from the xw7720 n via to D7701cathode.
When I connect the screen I get 0V at o/p, Still, the display image is there.
But Q7706 is not turning ON. Q7706 gate has 8.2V.
When I check Q7707 Gate - the 5th pin is 0V and the 2nd pin is 3.3V.
When I connect the screen I get 0V at o/p, Still, the display image is there.
But Q7706 is not turning ON. Q7706 gate has 8.2V.
When I check Q7707 Gate - the 5th pin is 0V and the 2nd pin is 3.3V.
So missing EDP_BKLT_EN signal.
"I had 8.5V at the boost circuit output"
Impossible without that signal.
Fuse gets burnt again?
"I had 8.5V at the boost circuit output"
Impossible without that signal.
Fuse gets burnt again?
manumathew.017
Member
Yes earlier I had 8.5V , that was before fixing the feed back issue. I have also changed the driver IC . Fuse is good now
Re-check all you done there.
Be sure didn't run wire between traces in wrong way.
Here some pictures.
Be sure didn't run wire between traces in wrong way.
Here some pictures.
manumathew.017
Member
Confirm continuity with schematic...
manumathew.017
Member
Yes the o/p has connection to the feed back pin of driver IC
Still missing EDP_BKLT_EN?
manumathew.017
Member
Now I can see both BKLT_PLT_RST_L and EDP_BKLT_EN are present and 3.3 V but Q7706 is not functioning I mean I get 0V at PPVIN_S0SW_LCDBKLT_FET. And 8.3V at PPVIN_S0SW_LCDBKLTFET.
I don't have Q7707 MOSFETs spare. Am I allowed to connect LCDBKLT_EN_DIV_L directly to Ground for testing purpose?
I don't have Q7707 MOSFETs spare. Am I allowed to connect LCDBKLT_EN_DIV_L directly to Ground for testing purpose?
manumathew.017
Member
Yes, the problem solved, I have shorted the 1st and 6th pins of Q7707. Found the backlight is present. Then I have replaced the Q7707 with a new one. Now it's perfect. Thanks for the support
Why not LCDBKLT_EN_L???
Bypass pins 1/3 of Q7707.
Bypass pins 1/3 of Q7707.
manumathew.017
Member
However the issue is resolved. Apparently the driver IC and Q7707 were faulty. Replaced both and it's working perfectly