Thinkpads Forum

I have a T61, type 7661-E17, that when the power button is pressed to turn the machine on, whether on AC or just battery, the ThinkLight will flash once. Once this T61 is powered up, the ThinkLight functions normally by turning it on/off with the Fn+PgUp buttons. It's unusual and the only ThinkPad I've ever owned that does this, that I can remember. I can't picture in my mind what the cause of this behavior would be.

I've read about software control of the ThinkLight, to use it for various notifications and such, but this is not what I've got going on.

Anyone have any ideas what might be causing this? Or, has anyone ever experienced something similar?

My T410 systems do this as well, along with the CAPS LOCK and mute LEDs. I believe it's part of the POST sequence.

AFAIK no machine before the T410 ever flashed at bootup.
I have seen many T6x/R6x/X6x machines, no one ever flashed its Thinklight!
Must be a software glitch!

RealBlackStuff wrote:Must be a software glitch!

What kind of software are you thinking? Firmware, maybe? BIOS glitch? It happens right at the button press before any software is loaded, which makes me think it must be a hardware glitch, but I dunno.

Very interesting that the newer ThinkPads do this, I didn't know that. Still something strange about this T61....

Could be a Grub(?) fault, you seem to run a lot of Linux.
Or maybe a HD/SSD with W7/W8 from a T410 or higher was put in that T61?
I have run almost every variety of T6x BIOS, incl. Lenovo, Middleton, Zender, TTAV134, you name it. Never a flash!

My X220 always does this at start up, not sure about the others, I will check.

X201i does flash thinklight too
X301 does not


I have never regarded this as a fault, just the routine it goes through on start up?

After further investigation, I think there may be a ground fault of some sort. Not only does the light flash with the press of the power button, but also with the machine off, the light flashes when the AC adapter plug is inserted, and also when the plug is removed.

Looks like I may have to tear the thing down and see if I can fine something out of place. Except I don't really know what to look for.

Edit: Well I've since torn the thing down, and didn't find anything amiss other than the power jack's screw was loose. Tightened that back up, looked for any other problems and couldn't find any. Re-assembled, and the ThinkLight still flashes on pressing the power button.

But!...After putting it back together, the LED CCFL is not lighting up! Press power button, ThinkLight flashes, ThinkPad splash shows up on dark screen, press F1, BIOS comes up...still no back light. And...GET THIS...press Fn+PgUp and the ThinkLight AND the LCD back light come on! Seems what is happening is pressing Fn+PgUp turns the ThinkLight off and suspends the system too. Pressing Fn brings the back light and the ThinkLight back up. Fn+F4 still does what it's supposed to do also.

Well, after a couple of power off cycles things are back to like they were before, ThinkLight flashes, CCFL lights up and I can boot into BIOS. Still flashes when the AC adapter plug is inserted or removed too. BTW, same thing happens with HDD removed or installed, so I don't think it's a software glitch. Still puzzled, though.

2nd Edit: As it is right now, I can't get the display to light up unless I turn the ThinkLight on. Pressing Fn+PgUp suspends the system. Fn wakes it up...with the ThinkLight off, but have to turn it back on to get the CCFL to light up. Tried swapping keyboards, but that didn't make any difference.

All those signals come from the inverter.
Reseat the LCD-cable on both mobo and inverter, and/or try to replace the inverter if you have a spare one.

Kilowatt wrote: X201i does flash thinklight too

More observations:
X201 - does flash thinklight at startup
and X201 tablet in non-tablet body does the same

RealBlackStuff wrote:Reseat the LCD-cable on both mobo and inverter, and/or try to replace the inverter if you have a spare one.

Swapped lids with a similar T61, and fault stayed with the base, not the lid with the LCD cable and inverter.

Any other ideas?

After all these months, I'd forgotten about writing that I swapped lids...now I'm not so sure that I ever did.

Anyway, RBS, you were right on the money with the inverter being at fault. I finally got around to getting a hold of a new inverter, and swapped it in this afternoon. It works! Normally I might add. So, bottom line...faulty/failing LCD inverter all along.

UPDATE: It looks like I was too hasty declaring the problem solved. I booted the T61 up this morning to install an OS, and left the machine on sitting on the desk for a couple of hours. When I returned the display had shut off, and would only come back on if I turn the ThinkLight on with Fn+PgUp. Now it's just like with the former inverter, ThinkLight flashes at power on, and LCD will not light up unless ThinkLight is on.