Powering On With a Dead CMOS Battery

[JHEM]

A dead CMOS battery should not prevent the laptop from booting to at least the IBM splash screen.

Sorry Ray, but Thinkpads are different and a dead CMOS battery most definitely will result in a dead machine.

The CMOS battery provides the power to activate the solid state solenoid that actually turns the machine off and on as the power button on all Thinkpads is only a momentary contact switch, not a mechanical on/off switch.

Regards,

James

[rkawakami]

Sorry Ray, but Thinkpads are different and a dead CMOS battery most definitely will result in a dead machine.

So how is it that when I just removed my CMOS battery in my T21 (granted not a T23 that we are talking about here), it turns on just fine?

[JHEM]

Sorry Ray, but Thinkpads are different and a dead CMOS battery most definitely will result in a dead machine.

So how is it that when I just removed my CMOS battery in my T21 (granted not a T23 that we are talking about here), it turns on just fine?

Docked? Docking stations bypass the CMOS battery start function.

Undocked? Try starting it about five times on AC or battery only, which will deplete the internal capacitors.

Regards,

James

[rkawakami]

Docked? Docking stations bypass the CMOS battery start function.

My test this morning with the missing CMOS battery was with the T21 undocked and operating on AC adapter.

Undocked? Try starting it about five times on AC or battery only, which will deplete the internal capacitors.

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. (This can't be good for my disk drive ). In between each start I have shorted out both the main power terminals and the CMOS battery terminals while pressing the power button. I'm hoping that this will discharge any capacitors in the power-on circuit. Of course each time I start the laptop, power from the battery will be charging any capacitors. 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.

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). Both showed the 161 and 163 boot errors. I was still able to start the systems with dead CMOS batteries. My T21 shows boot errors 251 and 271 with the missing CMOS battery, but the laptop still powers on. 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. Am I missing something? Do you have schematics on any of the Thinkpads so I can find out what's going on?

[tfflivemb2]

Sorry Ray, but Thinkpads are different and a dead CMOS battery most definitely will result in a dead machine.

James,

I have to disagree with you here as well. I have an R40 that the CMOS connector to the systemboard broke off completely. It and the CMOS battery aren't even inside the R40. I have been using it this way for about 2 months or more. Before I added the wireless card and had to apply the No-1802.com hack, the R40 would be unplugged for a while, then I would boot it, set the time, and keep on going. Since doing the hack, I haven't unplugged it, because I didn't want to have to perform the hack again.

Once of these days I will get around to resoldering the connector to the systemboard.

[rkawakami]

AHH! There your are! (I'm talking about this part of the thread that vanished from the original post. One of the mods must have moved it as it was getting slightly OT.)

Anyway, as I was saying... I have had the main battery, the CMOS battery and the AC adapter removed from my T21 overnight. I pressed the power button over 20 times and held it for at least 30 seconds. Reinstalled only the main battery (left the CMOS out) and powered on without any problems. Well, okay, I had to reset the date and time (again!), but it turned on fine.

I have since seen other posts about "overcharged capacitors" causing turn on (turn off as well?) problems. 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 guess this is the basis for the "multiple press-and-hold" of the power button to try to discharge any stubborn cap. However, this implies that there is a voltage source charging the capacitor to begin with. If you have a dead or missing CMOS battery, no voltage source, therefore no overcharged cap (at least coming from the backup battery).

My boss at work is the Applications Manager. He deals with our customer's problems concerning our memory modules. IBM is one of the tier 1 accounts. I asked him tonight if he has ever been given any circuit schematics for any one of the Thinkpads. There's about 15-20 different Thinkpads sitting on racks in the lab undergoing testing. He thinks he has but he needs to check his old e-mails. Given that he probably received technical documents with an NDA, and that most likely, they only cover the memory access circuits, there's a good chance that I won't be able to get any information about the power-on circuit. But I figure it's worth a shot asking for them.

[JHEM]

Ray, et. al.,

I split this off into a separate topic in order to better pursue it.

Unfortunately I'm up to my eyeballs in alligators at the moment.

Regards,

James

[tfflivemb2]

Ray, et. al.,

I split this off into a separate topic in order to better pursue it.

Unfortunately I'm up to my eyeballs in alligators at the moment.

Regards,

James

Don't get bit!

[rkawakami]

Unfortunately I'm up to my eyeballs in alligators at the moment.

Not in that lake of yours I hope! (cf. this thread)

My boss was out of town on a business trip yesterday (Friday) so I'll see what he says about any schematics when he gets back.

(edit: corrected 'this thread' link to work properly)

[JHEM]

Not in that lake of yours I hope! (cf. this thread)

No Ray, this wasn't me!

Top of the food chain in my little lake are the snapping turtles, we have a large resident female about the size of a garbage can lid. She makes short shrift of any ducklings or goslings unlucky enough to take their first swim in our waters.

My boss was out of town on a business trip yesterday (Friday) so I'll see what he says about any schematics when he gets back.

I'm searching my various archives for the IBM ECO that discussed this matter years ago.

More later this week, I'm still busy beating off the virtual gators!

Regards,

James

[rkawakami]

Quoting myself....

My boss was out of town on a business trip yesterday (Friday) so I'll see what he says about any schematics when he gets back.

Alas, no luck on the search for IBM documents about the power circuits here at work. I've been looking around the net for problems reported about IBM laptops not powering on.

Getting a little off topic for a second:

The power on problem seems to be related to when the laptop enters hibernation mode and refuses to revive. Most of the "solutions" revolve around putting the laptop inside the refrigerator/freezer in the hopes that it will bleed off the charge from the capacitor(s). Note: I do NOT recommend doing this! The story about the overcharged capacitors seems to originate from around 2001 by an IBM tech who told this to a person who had a power problem:

http://www.windowsitpro.com/Articles/Ar ... 19920.html

(found by Yahoo using "overcharged capacitor ibm thinkpad" search string)

Unfortunately, the bulk of the article can only be read if you subscribe to the site. However reading the comments that have been posted at that site I get the feeling that this is may also the origin of the "multiple press and then hold power button" fix.

I also can't help but believe that this article somehow reinforced the capacitor issue:

http://www.geek.com/news/geeknews/2003F ... 018535.htm

Several years back there was a known problem from some Taiwanese (I believe) capacitor manufacturers that had a high infant mortality rate. Although this is probably not what is causing problems in three and four year old laptops, there may be a preceived connection between bad capacitors and power problems.

And bringing it back on-topic:

Most of what I've found talked about the "overcharged capacitor" issue and not anything about dead CMOS batteries preventing power-on. I still have not run across any information about a depleted CMOS battery proven to be the cause of a failure for an IBM laptop to turn on.

[awdark]

If it means anything, my barebones T20 with bad bios started without a battery and CMOS battery just fine.

I dont know about these capacitors in the thinkpad, but typically those blown capacitors swell and leak upon failure. Perhaps one can check for something like that?

[rkawakami]

I'm searching my various archives for the IBM ECO that discussed this matter years ago.

James,

Since you brought this up again in another thread, have you found any of the IBM engineering documentation on this issue?

[JHEM]

Since you brought this up again in another thread, have you found any of the IBM engineering documentation on this issue?

Sadly, no Ray, but I'm still looking.

Regards,

James