Power to inverter problem?

[boris]

I dropped my T41 off 3 to 4 foot refrigerator. It cracked the hinge, so I turned it on and it worked-monitor and all. I was on business travel and didn't have a spare hinge so I took it to work to continue using it.

When I got to work, it turned on, but the monitor no longer did-though the monitor plug worked for an external monitor.

I got it back home, replaced the hinge. I coated any wires in the hinge that could have been exposed with insulator material "plasti-dip" to ensure no grounding would occur, as well as replacing the florescent LCD bulb with a spare I had.

The bulb, the inverter, & the wiring harness from my T41 were all plugged into my wifes T40 to ensure it lit up. It did.

Here's the question: the inverter, cabling, and bulb all seem to be good-since it lights up in my wife computer. What could be damage on the mother board that would prevent it from lighting up the
florescent tube? My gut would say some sort of power source to the inverter, but I don't know where that is on the board.

Any advice would be appreciated. I use this computer daily and my wife is irritated that I've taken hers

Thank you.

[richk]

How about the little switch at the back of the keyboard bezel or the button it presses below on the LCD cable.

[boris]

Good thought.

Please correct me if I am wrong, but pushing that button hibernates the computer. I mean an external monitor would also be turned off when I press it (all things working properly). So if I am see my desktop through an external monitor and it shuts off when I push the button, the problem wouldn't be the button. I don't completely know how it works which is why I am I am asking, not stating this as fact.

[richk]

It does whatever the event (push the button) is set to do in the power management application. However, if the button is stuck down, you can still start the machine and the LCD will be dim. That's the way you always do it if you use an excternal monitor and a docking station. You press the power button on the dock.

[boris]

Thank you Rich.

I was testing it and it started having OS loading problems. Now it acts as if there is power to nothing. No on/off button response. Even swapping out with a charged battery solicits no response. I'm not sure why a problem gets progressively worse with me doing very little.

Is it time to get another motherboard of have this one sent out for repair?

[Harryc]

- unplug system and remove battery

- press the power button ten times repeatedly

- then hold down the power button for 25 seconds in order to completely discharge the capacitors, etc.

Try plugging in the AC power and attempt to boot. If nothing happens, then repeat the process but run off of the battery instead (no AC adapter).

[boris]

I'll give it a shot. It will be a couple weeks before I can get back to it, but it is certainly worth trying. What does the 10 button push do? I mean does the bios have some way of interpreting that?

[rkawakami]

The theory is that by pressing the power button without any source of power applied to the system you will cause any malfunctioning capacitor to lose its charge. It has been a long-suggested fix which, if I understand the story, was originally given out by an IBM service technician. The explanation goes like this:

- there is a capacitor (or capacitors) on the motherboard which for some reason has retained a voltage charge when it shouldn't (i.e., the "overcharged capacitor")
- this excessive charge keeps the laptop's power-up circuitry from performing normally
- by attempting to power on the laptop without any external power supply (battery and AC adapter), the motherboard is supposed to draw out the stored charge in the defective capacitor(s) and return the system to "normal" operation (after a power source is re-applied)

Personally, I do not totally buy into this story. You would probably do better by flexing the chassis around as this might cause an intermittent connection to be (temporarily) fixed. It is possible that a charge left in a capacitor can inhibit a "one-shot" type of trigger. In this type of circuit design, there is also a resistor connected in conjunction with the capacitor. In electrical terminology it's known as an RC (resistor-capacitor) network. However, in order for the capacitor to retain the charge (for longer than what it is designed for) the resistor needs to be disconnected from the capacitor. If this happens, whatever charge that has been placed into the capacitor will remain there. It has been suggested that this stored charge negatively affects the power-up sequence. As all capacitors are not totally perfect, any charge will eventually leak off by itself but it might take hours to do so. Re-connecting the resistor will immediately start to discharge the capacitor. If indeed this multiple-push-and-hold technique has proven itself to work, then perhaps this pushing and holding is actually putting some physical (not electrical) stress on the motherboard and that causes a broken/loose connection to be fixed and "cures" the power problem???

Certainly some residual power is left in a system immediately after it has been turned off or disconnected from an external power supply. Pushing the power button once and holding it for a few seconds should be sufficient enough to cause any "stored charge" to be released. After which, where is the power that the electrical circuits need to operate coming from? The CMOS (backup) battery? This battery is used to keep the real-time clock operating and any important system data retained in volatile (CMOS) memory. Is there any way that this battery is being used to partially operate the laptop and allow the power button to discharge capacitors? I don't know for sure but I seriously doubt it.

<end of pseudo-rant and getting back OT>

The power to the inverter could be protected by a fuse. If all other things have been checked out (stuck lid switch, LCD ribbon cable, inverter, etc.) and you are still not getting the backlight to turn on with the T41 motherboard, then I'd start poking around for any loose component on the motherboard and check any fuse that you come across. Fuses typically are labeled with an "Fn" designation. The fuses on a Thinkpad motherboard can also appear quite different from each other. You will need an ohmmeter to check them. Without any power applied to the laptop, put the meter leads across the ends of the fuse and if you read anything more than 0 ohms, it's bad.