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Posts: 4 | Thanked: 0 times | Joined on Apr 2010
#1
I picked up 3 Nokia 770s on ebay for only a few dollars, the catch was they only came with batteries and all three had white screens...


I did some preliminary reading and thought I would be able to fix them up, but then after I got them and tried what I thought would fix them it didnt work. Turns out I uncover posts about the whole WSOD issues.

Anyway, I found a source to buy nokia 770 parts in Europe (Telement), but for three lcd screens, some C-Covers, and a stylus comes out to like $164USD.

That seems like a little much to me, but say I did get three new LCDs....whats to say their not going to blow out again?

Since I had three 770's, I was able to swap around the screens and since some where better than others, I noticed the problems went with the LCDs meaning that a new LCD would restore it....

..The main problem is I don't know the root cause that destroys the LCDs and I don't want to throw a new one on there and have it destroyed.....

I read that the LCD controllers get burnt out, but what causes that? and Could my LCD controllers be burnt out? Its hard to say since the LCD controllers are located on the main mobo, while swapping out the LCDs seemed to tell me that they could be replaced with working ones.

So there must be something on the main motherboard that needs to be replaced/upgraded in order to prevent new LCDs from being fried again...


Any thoughts?


Nokia Part numbers:

N770 4850849 LCD
N770 0266501 C-COVER ASSY 040-005866 P2102 19
N770 0264107 FRAME ASSY 040-005862 P2102 18
N770 0266498 B COVER ASSY 040-005860 16
N770 0266497 A-COVER ASSY 040-005858 P2102 14
N770 9400546 SHIELD PROTECTIVE TAPE 040-005908 P2102 20
N770 9797373 KEYMAT TOP 040-005902 P2102 20
N770 9590743 SHIELD LID BB 20
N770 0266500 BATTERY COVER ASSY 040-005861 P2102 18
N770 9797372 KEYMAT FRONT 040-005901 P2102 20
N770 9900265 STYLUS 040-005907 P2102 19

Last edited by pomprocker; 2010-04-14 at 23:52.
 
Posts: 226 | Thanked: 47 times | Joined on Jan 2008 @ Poland / Bialystok
#2
From my point of view - power sequencing is poorely organised by driving ENABLE pins of low dropout linear regulators.
For n770 all power sequencing for LCD is being held by state of voltages vs loads.
It can lead to a failure.

I've had an opportunity to exchange display in my wsod'ed n770 and it DID work.

For LCD's manufactures give detailed recommended power sequencing diagrams.
Not knowing one it's hard for me to judge what would be optimal.
Yes - there is a possibility to monitor all signals with the scope and doing some tests. Then one probalby could notice the source of this failure.

But... is there anyone who wish to donate 3 x n770 ?
One for finding critical sequence, second to test other sequences except probable one and the third to make some normal vs. crash sequence benchmark?

After all that - one could develop some fix if applicable.
Yes - maybe it's just easy as solder few additional resistors, diodes and capacitors on critical paths but - without knowing for sure - I can only guess.

Last edited by XTC; 2010-04-19 at 16:41.
 
Posts: 4 | Thanked: 0 times | Joined on Apr 2010
#3
I've been able to track down two service manuals for this device both the level 1/2 and level 3/4. I think the document we need to see is some sort of service bulletin describing the problem and the fix.

I assume the fix was to just replace the entire motherboard with a newer revision, instead of swapping out components.

That be the case, how do I find out the revision of the motherboard? How could we somehow compare it to a newer revision?

The level 3/4 manual mention two special asics on the board called Retu and Tahvo (Finnish names for Fred and Barney (as in the Flintstones)) In the manual it says if the LCD Controller is bad to replace TAHVO...Thats all I got out of it...

Last edited by pomprocker; 2010-04-19 at 17:16.
 
Posts: 68 | Thanked: 43 times | Joined on Jun 2010
#4
What a lot of work for that obsolete and crufty device. $164/3 is about $55 and you can probably buy working ones for that.
 
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