There's about 15-20 different Thinkpads sitting on racks in the lab undergoing testing. I asked him tonight if he has ever been given any circuit schematics for any one of the Thinkpads. He deals with our customer's problems concerning our memory modules. My boss at work is the Applications Manager. If you have a dead or missing CMOS battery, no voltage source, therefore no overcharged cap (at least coming from the backup battery).
However, this implies that there is a voltage source charging the capacitor to begin with. I guess this is the basis for the "multiple press-and-hold" of the power button to try to discharge any stubborn cap. From a circuit design standpoint I can understand that a capacitor which is already fully charged (when it's not supposed to be) and not discharging when it's supposed to, can prevent a "one-shot" pulse from occuring. I have since seen other posts about "overcharged capacitors" causing turn on (turn off as well?) problems. Well, okay, I had to reset the date and time (again!), but it turned on fine. Reinstalled only the main battery (left the CMOS out) and powered on without any problems. I pressed the power button over 20 times and held it for at least 30 seconds. I have had the main battery, the CMOS battery and the AC adapter removed from my T21 overnight. One of the mods must have moved it as it was getting slightly OT.)Īnyway, as I was saying. Am I missing something? Do you have schematics on any of the Thinkpads so I can find out what's going on?ĪHH! There your are! (I'm talking about this part of the thread that vanished from the original post. All of the information I have seen concerning Thinkpads with bad CMOS batteries is that you will get boot errors, not that you won't be able to power up. My T21 shows boot errors 251 and 271 with the missing CMOS battery, but the laptop still powers on. I was still able to start the systems with dead CMOS batteries.
Two of the 600X systems you see in my sig were recently bought off of eBay and had totally dead CMOS batteries (I tested them with a voltmeter). I guess the real test would be to remove all batteries and wait for several days or open up the case and short out all of the capacitors on the motherboard.
Of course each time I start the laptop, power from the battery will be charging any capacitors. I'm hoping that this will discharge any capacitors in the power-on circuit. In between each start I have shorted out both the main power terminals and the CMOS battery terminals while pressing the power button. So far I have been able to start my T21 with a missing CMOS battery 20 times using an almost depleted battery with no AC adapter or docking station. JHEM wrote:Undocked? Try starting it about five times on AC or battery only, which will deplete the internal capacitors.
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