[SOLVED] T30: F14 fuse replaced but still no image on LCD

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singbad · #1 Post by **singbad** » Thu Jul 21, 2011 7:33 am

Hi,
I got a T30 with a blown fuse F14 on mainboard (in the 16V supply-line for the display inverter). I replaced the fuse, the voltage is good but still no image on LCD. LCD and inverter are ok.

External monitor works ok and ATI Radeon does not get hot.

Any idea?

Best regards,
singbad

EDIT: It's just the backlight that's missing, I can see a shadowy image in the dark of the LCD.

singbad · #2 Post by **singbad** » Thu Jul 21, 2011 1:05 pm

Im seeking fuse F13 on the board. I remember someone posted fuse-location images - was that for the T30?

BTW: the T30 schematic is meanwhile available on Scribd - does anybody have or can anybody point me to a board-layout plan?

EDIT:
Found it! F13 is down below on the other side of the board, right underneath the display cable socket (and it's blown indeed!). I was wondering where the missing voltage of pin 61 of that connector got lost (VCC3B in the schematic).

BTW, I noticed that the text-search feature of pdf schematics is of unvaluable help in signal and voltage tracing.

singbad · #3 Post by **singbad** » Thu Jul 21, 2011 6:23 pm

Inverter supply voltages are all ok now but still no LCD backlight. There's a signal "BACKLIGHT_ON" missing from U28 pin 55 (IBM 38L2890 PMH2 YAMA TO - whatever this is).

singbad · #4 Post by **singbad** » Mon Jul 25, 2011 2:50 am

The "BACKLIGHT_ON" signal appears to be stuck LOW permanently. After I cut off pin 55 of U28 the backlight works but when I press the lid switch using a screw driver it turns off for about a second and immediately comes back on again. I wonder what the power-management implications are. After the selected number of minutes to blackout the LCD turns black but does the CCFL? Hard to tell in daylight...

(Is the fridge light really off when the door is closed?

)

ozzymud · #5 Post by **ozzymud** » Mon Jul 25, 2011 9:07 am

singbad wrote:BTW: the T30 schematic is meanwhile available on Scribd

Where? Can't seem to find it.

#6 Post by **Harryc** » Mon Jul 25, 2011 9:33 am

Do not post links to schematics on this forum...please!

#7 Post by **rkawakami** » Mon Jul 25, 2011 11:25 am

To further explain... IBM/Lenovo has stated that circuit schematics are still their proprietary property and that they are not to be circulated in public. As such, the forum cannot allow posting of links to these files.

singbad · #8 Post by **singbad** » Mon Jul 25, 2011 4:28 pm

Oops, sorry for posting the links. I've seen the schematics offered for sale from a couple of sources so I thought they must have been disclosed by Lenovo recently.

May I give search hints instead of links?

#9 Post by **Harryc** » Mon Jul 25, 2011 4:30 pm

No. Nothing please. No links, no hints, etc. ...

singbad · #10 Post by **singbad** » Fri Jul 29, 2011 6:57 pm

Today I got another T30 with a missing "BACKLIGHT_ON" signal, not permanently but most of the time. I had to do it again: amputate pin 55 of U28. Now the signal is permanently high and the display works again. No need to worry about the display being always on - the power circuitry has other means (i.e. main and auxiliary voltage supply lines) to shut off the display when necessary.

[SOLVED] T30: F14 fuse replaced but still no image on LCD

[SOLVED] T30: F14 fuse replaced but still no image on LCD

Re: T30: F14 fuse replaced but still no image on LCD

Re: T30: F14 fuse replaced but still no image on LCD

Re: T30: F14 fuse replaced but still no image on LCD

Re: T30: F14 fuse replaced but still no image on LCD

Re: [SOLVED] T30: F14 fuse replaced but still no image on LCD

Re: [SOLVED] T30: F14 fuse replaced but still no image on LCD

Re: [SOLVED] T30: F14 fuse replaced but still no image on LCD

Re: [SOLVED] T30: F14 fuse replaced but still no image on LCD

Re: [SOLVED] T30: F14 fuse replaced but still no image on LCD

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