T30 Won't Light LCD and No Status Lights - Help!?

[Neil]

Bought this parts T30 thinking I would have an easy fixer upper. It was advertised as "works great on both battery and ac power but has a broken screen. This was a great little computer until the screen went out." So I figured, since I had another working screen, I would swap lids and all would be well. But, I sold my working lid before this T30 arrived. But I still have some parts around to swap out. Here are the symptoms:

Works fine with an external monitor.
Internal LCD works, displays same image as external, just very dark because of no lamp.
CCFL will not light up. Tried CCFL on a different machine and it lights up just fine there.
Status LCDs above keyboard do not light up. Since those LCDs are on the ribbon cable, I thought my problem must be with the cable. Switched out ribbon cables, and neither one made a difference. Still no status lights, and CCFL doesn't light. Switched out inverters too, and neither one made it work.

So, it looks like, instead of a T30 with a "broken screen", I got a T30 with a broken motherboard. Is that what it looks like to you too? Is there something else I can check or test to try and eliminate as the source of the problem? I have another T30 system board, that has other problems, so I can't really use it. And although parts from the one might make the other work, I don't know what parts I would be looking for, and I doubt that I have the skills or equipment to do system board repair anyway.

What are your thoughts?

[rkawakami]

Could be a fuse on the motherboard which protects the power going through the ribbon cable. Might also be a stuck lid switch.

[Neil]

Oh yeah, thanks Ray! I did check the lid switch, by depressing it while viewing the BIOS screen (with the keyboard bezel removed, just pressing the button on the switch itself), and it was not stuck, but it still had no affect. I suspect that without an OS loaded, all the switch would do is turn the CCFL off. Since it was already off, the switch having no affect didn't surprise me. Should it have done something?

And, where would I look on a T30 board to find a fuse that could stop power from the ribbon cable?

[Harryc]

Right around the ribbon cable connector

[Neil]

Well, duh! I'll have to go have a look.

[rkawakami]

The lid switch will, independent of an OS, kill power to the inverter when it's depressed. If that happens, then the CCFL goes out too. My thought was that by toggling the switch, you might discover that it was stuck.

[Neil]

OK, no the switch was not stuck. It seems to be working properly.

Took a look at the area near the ribbon cable connector, and sure enough, there is a fuse labeled F11 just to the right of the connector. It measures 0 ohms, and seems to be well attached to the board. So I guess, that is not the problem.

While looking around, I compared this board to the other one I have with other problems, and noticed a difference. Just south of the keyboard connector is a vertical row of what look like small power resisters (if they are labeled, it's too small for me to read). On the board I'm comparing, there are three of these, and all three measure a little over 4K ohms across them. On the board in question, that I'm trouble shooting, there are only two. The third space is empty, and the solder pads have a shiny mound of solder on them. Doesn't really look like anything was ever attached there, but I don't know. Anyway, the two that are there measure near infinite resistance. So somethings is up there, but I don't know what. Any of you have enough experience to give some advice or counsel?

[RealBlackStuff]

What are the P/N or FRU numbers of the mobos, and tell us which one has 2 resistors, and which one 3.
That way we could try and compare.

[Neil]

The board I'm working on is P/N 26P8433 FRU 91P7698 and has the 2 parts.
The other board is P/N 26P8355 FRU 26P8328 and has 3 of the part.

So looks like I shouldn't expect them to be identical.

[SMA]

If the only fuse you have located so far, is the F11 fuse mentioned above, then I will suggest that you go back to the fuse checking.
I would expect at least 3 fuses near the LCD connector.

Note that the bottom side of the board, just below the LCD connector, is actually the board space nearest to the LCD connector where a fuse can be located.

You could start by locating the fuses on the spare board that you have.
Thereby, finding out if there are any fuses on the bottom side of the board.
If there are no fuses on the bottom side of the board, then you may be able to avoid taking the board out of the machine.

[Neil]

Thanks, SMA, for the encouragement to continue looking for more fuses. I did find two more, for a total of three, near the LCD connector just as you suspected. There is the F11, a rather large fuse, on the right side of the connector, and F5 and F14 (much smaller fuses) on the left side of the connector, and partially hidden by the ultra bay assembly. I also did as you suggested, and looked at the bottom of the other broken board, and couldn't see any bottom side fuses. I did, however, learn why my other board is won't boot. I found a burned I.C. chip on the bottom of the board.

Now that I have located three fuses near the connector, I measured 0 Ohms across all of them. So the reason for no power to the inverter must be something else. Anyone have any other ideas?

[Neil]

Got a 5X magnifier today so I could do some more comparison with the boards. I think I have located a blown fuse on the bottom side of the board right next to the LCD connector. Here is a picture of the other board showing the fuse in question (don't try to view it if you have a slow internet connection). It is marked with an "F", which I assume means it's a fuse. On the board in the picture this device measures 0 Ohms. On the board that won't light up the LCD lamp, the "F" is not visible. Looks blown out, and measures infinite resistance. This is likely where power is being stopped from getting to my inverter, don't you think?

I made an attempt at removing this fuse from the board, but it's so tiny!, I failed to get it loose with my 25 watt pencil soldering iron. Must have been quite the sight with me trying to hold the iron to the board and get my face close enough to focus the jewelers ring on my glasses. I'm just thrilled that I didn't burn my nose!

Still interested in your commends and suggestions.

[rkawakami]

Appears to be a Littelfuse 0434.500 fuse, 0.5A. Mouser.com has this as being "obsolete" in single unit quantities and Digikey says it's a non-stocked item. However, Digikey suggests an 0467.500 as a replacement; it's a little bit wider but the length is the same.

If there's still metal endcaps left on the original fuse, you can "piggyback" the replacement fuse right on top. Just flow some solder over the ends and it should work.

ref: http://www.littelfuse.com/data/en/Data_Sheets/434.pdf
ref: http://search.digikey.com/scripts/DkSea ... 1391DKR-ND
ref: http://www.mouser.com/Search/Refine.asp ... d=0467.500

[SMA]

To get the fuse out, you will need 2 soldering irons. One for each hand.
This to get both sides of the component free at the same time.
It is not as difficult as it may appear, but if you have never done it before, then it may be safer to
exercise at little on a piece of electronics that you can do without.

I do believe that you have located the problem and that all you have to do to get the board going, is to
replace that fuse.