T42p inverter/backlight/fuse/? problem

[sbjoe]

Also posted the following over at the lenovo forum so please accept my apologies for the redundancy to anyone who frequents that venue as well:

Just replaced the inverter with no joy in the result. Before I get into describing more precisely the symptoms and looking for further advice I'd like, if possible, to test the inverter for output to the lcd. I'm guessing that a vom to the 2-pin connector should tell me whether there's anybody home there; is that at least approximately correct? If so presumably it should be set to dcv in the - what? - 1000 range..?

[rkawakami]

Welcome to thinkpads.com!

I would NOT attempt to measure the output voltage from the inverter using an ordinary voltmeter. I know, 'cause I tried that once and ended up with a burnt clip and inverter socket.

ref: http://forum.thinkpads.com/viewtopic.ph ... 45#p230845

About the only way that I would attempt to verify that the output from an inverter is working would be to connect a known good CCFL. But even that has some questionable results since inverters are usually matched to a particular CCFL. Another method I tried is documented here:

http://forum.thinkpads.com/viewtopic.php?f=18&t=48910

It requires some disassembly of the LCD bezel and a neon bulb but it only seems to work when there's a good CCFL in operation.

[Brad]

For me in the past when I swap LCD parts the problem has always been the LCD and not the inverter. Of course I haven't been lucky enough to find a bad inverter along the way. Perhaps you have.

Brad

[sbjoe]

Thx Ray! Hope I haven't fried a brand new inverter as I went ahead and disconnected the 2-pin connector and fired it up with the bezel off. Anyway, I guess it's time for a little background. This is a refurb I got from IBM something over a year ago. From the first though, when it's on battery power almost always when I awakened it from standby the monitor would come on normally and then go black for a second or two and then come back on and function normally. I'd come to think of this as normal until it began recently to happen more frequently and for longer periods. It finally quit lighting up altogether, except that one time a few days ago it came on for a few minutes and then went black again. Looking more closely and with an external monitor attached I can see that there's a very dim image on the screen, so presumably that rules out the display adapter. The vom test, conducted before reading your caveat, is inconclusive at best given the info in your link. The best that can be said is that there was no *apparent* frying of parts. This monitor has never displayed any of the pink/red screen that I'm given to expect usually accompanies a failing backlight, thus my decision to replace the inverter, alas to no effect. Up until the end it displayed no other obvious symptoms of impending doom, the display being bright clear and responsive to Fn Home/End. The led's on the inverter - actually, both of them - continue to operate normally and as expected. Any ideas short of throwing in the towel and taking it to a pro? I saw one thread somewhere in which a similar sounding condition apparently resulted from a blown fuse on the mobo; that would certainly be preferable to a new screen or attempting to replace the backlight, especially until I've verified inverter output. Guess I'm off to R/S in search of that elusive small neon bulb.

I wish, Brad! Unless I've been cursed with 2 bad inverters, including one that's brand spanking new.

[Brad]

Joe,

Sorry to say that in my book you have a bad LCD.

I have seen what you describe and replacing the LCD solved the problem. I did the inverter dance before so I thought I would save you the time.

You could save yourself lots of time and trouble by finding another compatible LCD or complete LCD assembly as your budget allows.

Brad

[sbjoe]

Joe,

Sorry to say that in my book you have a bad LCD.

I have seen what you describe and replacing the LCD solved the problem. I did the inverter dance before so I thought I would save you the time.

You could save yourself lots of time and trouble by finding another compatible LCD or complete LCD assembly as your budget allows.

Brad

Appreciate the offer Brad. I'm not quite ready to take that route just yet but your offer does give rise to another question - actually two:

first, is the ribbon cable at all likely to be the culprit? I've not seen much in the way of indications that those things are much prone to failure;

second, is the attachment point of that cable to the back of the lcd as delicate as it looks? Does it unplug easily and typically without issue?

I'd sure hate to replace the lcd and find later that it's a fuse or some other issue with the mobo...

No joy at R/S looking for a neon bulb; guess I'll google some more..

[ArtShapiro]

is the ribbon cable at all likely to be the culprit?.

It is certainly possible. It's a paper-like contraption.

I had a ribbon cable fail on a T20; I replaced the inverter and, when that didn't help, I confidently replaced the panel. It was a major bummer when that, too, failed to fix the video. Sent the machine off for repair, and it was the ribbon cable.

Still have the perfectly good LCD panel sitting three feet from me, where it has sat for about six years.

Art

[sbjoe]

At least I'll be somewhat practiced at taking this thing apart when this is settled. Sounds like I'd do well pulling the cable and testing each lead for continuity. Maybe I'll get real adventurous and take a peek at the mobo while I'm in there...

[rkawakami]

I'd say that ribbon cable problems would fall under the "intermittent operation with movement" symptom and then progress to "non-operation". For example, moving the lid around makes the display cut in and out but if kept still, the screen works fine. Then one day, no movement of the lid will make the display come back. The attachment at the back of the LCD panel is not that delicate. I've pulled off and then re-installed several of them and the worst part is trying to line up the ribbon with the receptacle (bad eyes in my case ).

Before going out and spending some $$$ on another LCD, make sure that the lid switch is not stuck. If it is and your system has been set to "do nothing" when the lid is closed, then that can also cut power to the inverter.

[sbjoe]

Good point about the ribbon cable likely being subject to lid movement if bad. Unfortunately I've not noticed anything of the sort, and not for lack of trying. As for the lid switch, the machine is set to go on standby when the lid is closed, and as I'm using it right now via an external monitor that doesn't seem to be the case. Guess I can relegate the cable to the 'not so likely' category. FnF3 makes both monitors go completely black.

[sbjoe]

Update:
Cranked it up this AM still connected to the external lcd & ~halfway through the boot process the screen on the laptop suddenly lit up perfectly. Lasted ~15min at which point it just as suddenly went dark again. During this period I was careful not to touch the lid or move the machine. Does this eliminate or raise any possibilities? Thx

[rkawakami]

Well, it won't be a "regular" fuse. By that I mean one that burns out and then has to be replaced. It could be a thermal fuse but I don't know if there's one in the power circuit for the inverter. And it still could be the ribbon cable or some other loose connection (non-movement from you notwithstanding). Sorry, but you're probably not out of the woods just yet .

[sbjoe]

Thx again Ray. Since last posting I've managed to get the monitor to stay mostly lit although it goes out once in a while. What I did was to turn the brightness down a couple of notches from the max. That seems to have improved things - to the point that I've disconnected the external monitor and put the front bezel back on the lid. I think I've all but ruled out the inverter as the machine is acting pretty much with the new one as it did with the original. My untutored guess is that I'm getting an intermittent open circuit at some point that may well be heat related. When the screen goes black, I've so far been able to bring it back by turning off the monitor using Fn/F3 for a few minutes after which it almost invariably lights back up for several minutes to an hour or more. Right now as I type I'm seeing some faint flickering on the screen. The question that's plaguing me is whether any of this is at all likely to be originating at some point other than in the lcd itself.

[rkawakami]

Just to clarify, but are both inverters FRU 93P4161? That's the part which is referenced in the HMM for the UXGA panel. From the sounds of you reducing the brightness level and getting a more stable operation, I was just wondering if you're overdriving the wrong inverter and it's shutting down on you. Either that, you're using the correct inverter but it may be drawing too much current.

[sbjoe]

No Ray, the new inverter is a 39T0359. I'd tried to find the 93P4161 at the IBM/Lenovo parts website & called when it came up empty. The original part has been superceded by the one I bought from an online supplier for a lot less $$ than direct from IBM. It's virtually identical in outward appearance but is touted at some sites as being lead free. The panel is indeed a UXGA. The 39T0359 I think was used originally in the T43 Thinkpads.

[rkawakami]

A search of the T43/T43p HMM says that FRU 39T0359 is for a 15" XGA panel. A UXGA T43p uses two different inverters; 27K9976 and 39T0361, although the panel seems to be the same (maybe there was a change in manufacturer during the T43p run).

[sbjoe]

Would be a bit of a bummer to find I've got the wrong inverter. I don't have the T43 HMM; maybe I should make another call tomorrow - oops, Monday I guess - and see if I can get confirmation of correct replacement for the NLA 93T4161. Meanwhile, I suppose I can pop the bezel off again and see if I can get the original 93T4161 to work at the reduced brightness setting. Your comment about the possibility of the inverter maybe drawing too much current is interesting as well. I can almost swear that the maximum volume coming from the onboard speaker(s) is considerably higher than before. Could that have any connection?

[sbjoe]

OOPS, again. Should read 93P4161, not 'T'.

[rkawakami]

My understanding is that inverters are supposed to automatically shut down when an "open" lamp is detected. However, it's been my experience that running an unloaded inverter typically generates some audible noise; a buzz or spark. Although this was with the CCFL unplugged from the inverter's output terminals.

As to the louder speakers, I can't comment other than to say that my hearing is temporarily reduced after last night's Fleetwood Mac concert .

[sbjoe]

I didn't get anything audible when I fired it up with the output leads disconnected. No noise or sparking when I touched the vm probes to the contacts either, but no reading also. Think I'll sleep on it and unless I get a better idea I'll plug the old 43P4161 back in tomorrow and see what happens. I've got it turned down to 3 bars on the brightness scale now and don't see any visible flickering.

[sbjoe]

Got the original inverter back in and it's been rock solid at reduced brightness for the better part of an hour now. Guess I'll monitor - pun definitely intended - it over the long weekend until/unless something happens to move me off the dime.

[sbjoe]

Further update. Yesterday, following the HMM, I removed and reinstalled the mobo, giving it a close if not particularly informed visual inspection which was unrevealing. When I started it back up, the display panel lit up normally briefly during startup after which it went completely black without even a shadow image of what was on the other monitor to which it's tethered. I went into advanced settings of display properties and managed to get the shadow image back on the screen, but at only about half size surround by a large black band on all sides. So it looks like the day's efforts have only compounded my problem. Anybody got a clue as to what's up with the reduced size of the display?

[ajkula66]

Had you swapped the cables, I would say that it's a cable issue, but you haven't.

Now, is the LCD expansion enabled in BIOS?

[sbjoe]

Haven't a clue George. Is that something I'm likely to be able to find and sort out fumbling around in there or had I best find a road map?

[rkawakami]

Screen expansion option/feature can be found within the BIOS. Power up the system, press and hold the F1 key until you get the Entering IBM BIOS Setup Utility message. Once there, and by default, the "Config" line should be displayed in white letters; this means that that option was be selected if you press the Enter key. Since that's the one you want, press the Enter key to access the Config menu. Use the arrow keys to then select the "Display" option. When you have done so, again press the Enter key to access the Display menu. Arrow down to the "HV expansion" option. It's probably set to "Off". That's the reason why the screen looks squished and is surrounded by black borders. Press the Enter key and a popup menu will be displayed where you can use the arrow key again to change the option to "On" and then press the Enter key. Once that's done, press the F10 key to bring up the Setup Confirmation window. The "Yes" option should be in reverse video, so press the Enter key to make the system accept the change.

[sbjoe]

Thx Ray, that's at least approximately what I'd expect. However there's a hitch in this pony's gait in that my panel now can't be relied on for much more than a few random seconds at at time so I'm pretty much dependent on the external monitor which as currently configured remains blank during the startup sequence until the windoze login screen, so when I attempt to access bios I've nothing but a blank screen. I'll see if I can find some setting from within Windows to remedy this but if you or anyone can lead me there I'll be more than willing to follow.

[sbjoe]

Belay that last post. The display came on for long enough for me to access bios. Unfortunately HV Expansion was already on. When I saved & restarted the screen displayed normally until the login screen at which point it reverted to the reduced size. It had displayed normally while I was in the bios as well. Panel went dark shortly after I got back into Windows. Stumped again.

It also puzzling that the external lcd doesn't display during boot. From what I could gather from the bios settings it seems that it should...

[rkawakami]

There's a BIOS setting which controls which display is the default. It's probably set to LCD. However, you should be able to activate the external monitor after the system is turned on, certainly if it's sitting at the main BIOS screen, by the Fn+F7 key combination. Since your HV expansion is already on, then I don't know what else could be causing your problem.

[sbjoe]

Whew! Clicking on the Dual Display option at the FnF7 screen got the display back to normal. It's stayed lit pretty much all day now thru several monitor on/off cycles with the FnF3 combination. Wish I could consider the problem solved but it'll be a good while before I'm ready to take it off its lcd tether with any confidence. At least I'm relieved to think maybe my own worst efforts have yet to have destroyed the system board. I've got some neon bulbs coming in the mail soon so at least I may be able to get a clue as to whether the problem lies somewhere other than with the panel which at the moment still seems rock solid.

[sbjoe]

Just came down after dinner and turned the monitors back on. Turned the panel brightness up to 3 bars and it went dark shortly thereafter accompanied by a sequence of several seconds of hollow popping noises, not very loud, but clearly audible. Dunno if the change in brightness was causative but there you are...