Thinkpads Forum

I have been gifted a DEAD ThinkPad 770Z (9549-81U). It is virtually new and has not been used for years. All the batteries were completely discharged. I replaced the CR2025 CMOS battery and verified that the voltage out of the AC power supply was good. Nothing lights up or powers up when I try to start it with AC power (with and without the main rechargeable battery installed). Holding the power switch on for a longer time doesn’t do anything. The reset switch has no impact and is the only thing on this spotless unit that appears to have been manipulated and shows some wear and tear. Can a bad/damaged reset switch result in absolutely no power going to the unit?

I’ve searched the Forum for similar problems but to no avail. A Best Buy “Geek Squad” rep basically told me that if I try to power up with the AC power supply (rechargeable battery removed) and none of the LED’s light up, then more than likely it’s a bad system board and not worth replacing due to cost. Is there anything else I should try before giving up on this “finger print free” unit? Any help would be appreciated. Thanks.

Bad MB! If you don't want to replace the MB with one from eBay, I'd be interested in the unit as a parts machine.

Regards,

James

You could search eBay for a new M/B. Don't know if you'd find much though.

Also, if you are ever willing to part with the comp, I'd be interested in making a trade for it.

I appreciate the offer of trade or spare parts usage but this gift is with some strings. If I cannnot fix it myself, I would feel obligated to return it to my friend and let him make the final disposition. Also, I don't know whether the system board is bad. That was an of the cuff comment by a Best Buy repair guy who never saw the unit.

I'm still hoping someone can explain to me how the reset switch works and whether that could be the cause of the dead unit. Also, any other suggestions would be appreciated. Thanks.

A few nights ago, my 760XD would not power on, nothing happened when I hit the switch except the keyboard LCD showed the normal icons. I removed the main battery, unplugged the computer and held the reset switch and the power switch at the same time for a few seconds. Try doing that with your 770. If this does not fix it, you probably have a bad motherboard.

The reset switch purges cmos settings and stops power from running through the system while it's pressed. The only way I can imagine a reset switch killing a unit is if it got pressed to hard and ended up stuck, thus preventing power from running through the computer. It's possible, but I doubt this is the culprit, though I could stand corrected if you are very lucky.

The reset switch does not purge CMOS settings.

It does not stop power from going anywhere.

It holds the reset signal on the CPU and usually all the internal peripheral devices so they cannot execute any instructions and are set to power-on conditions. A stuck reset switch would very likely make the system appear to be completely dead.

I gave what I assumed because I noticed I can never get power to go through the comp when the switch is down and I always lose my settings when I hit that switch.

Well, I guess I stand corrected. Still, back on track, either way, a stuck reset switch can cause a computer to not work.

I will remove the keyboard & back of the upper shield to access the reset switch area. I hope I get lucky and have it in a stuck mode. Thanks.

I removed the keyboard and loosened the LCD to get access to the reset switch. The upper shield has a flexible metal tab attached in the reset switch area. It appears to me that the function of the reset switch is to ground the upper shield to the system board below it by the use of the point of a pen to short the tab to the board. Since the tab was not touching the board below it, I assume that the reset switch cannot be the cause of NO power to the unit. Please let me know if there’s a flaw in my reasoning or how the reset switch operates.

Also, after removing the keyboard, I checked the voltage on the standby battery (05K4652) and found it to be .3V instead of 3.6V. I assume again that a dead standby battery wouldn’t impact on NO power to the unit.

Your comments and any suggestions are appreciated. Thanks.

JD1124 wrote:Also, after removing the keyboard, I checked the voltage on the standby battery (05K4652) and found it to be .3V instead of 3.6V. I assume again that a dead standby battery wouldn’t impact on NO power to the unit.

It most assuredly would!

Dead CMOS battery equals a dead Thinkpad!

Change the battery.

Regards,

James

If the CMOS battery is dead, the computer should still turn on. I'm not sure about all ThinkPads, but the ones I've worked with powered up fine without CMOS battery.

1. Sorry, if I confused anyone. I originally replaced the dead CMOS battery CR2025, which is a round lithium button battery putting out 3.0V.

The one under the keyboard is an oblong Ni-MH battery with two leads (P/N 05K4652 referred to as a Standby Battery) putting out 3.6V. I'm not sure of the function of the standby battery. It is the Standby Battery, not the CMOS battery that is only putting out .3V. I'm under the impression that the LED's should still light up even if both of these batteries were dead. Is this not the case?

2. Also, do you agree with my previous assessment of the functioning of the reset switch and that it cannot be the culprit of preventing NO power to the unit?

Thanks for sticking with me.

AlphaKilo470 wrote:If the CMOS battery is dead, the computer should still turn on. I'm not sure about all ThinkPads, but the ones I've worked with powered up fine without CMOS battery.

The only way I know to accomplish this Alex is while the unit is in a docking station as they normally have their own power supplies and bypass the laptop's power switch.

The CMOS battery in most Thinkpads, since at least the 755 series, provides power for more than just maintaining the date, time and configuration settings.

When you push the power switch you're making a momentary contact that energizes a solid state solenoid on the MB that actually turns the unit on. The CMOS battery provides this momentary power.

Hence, a completely flat CMOS battery leads to the all too familiar unresponsive Thinkpad.

Regards,

James

Then I guess some ThinkPad's are exceptions to this because I've powered many 760's without CMOS or suspend batteries while repairing and building them.

I do, however, wish I thought about that CMOS battery before trading off that 755CD of mine for a bunch of parts.

The standby battery (if like mine in the 750P) allows you to warm-swap main batteries. A very cool idea if you have charged spares available.

That standby battery is not needed at all for power-up.

I just mentioned the standby battery after the CMOS so noone would ask about that. I didn't think anyone would, but still, to kill the questions before they are asked.

But yes, I agree with you about the standby battery. My 380ED does not have that standby battery feature and I never realised how nice that feature was before I owned a computer without it.

Thanks guys for clearing up the the battery issues. Now, the item you haven't commented on was what I previously asked regarding the reset switch:

"I removed the keyboard and loosened the LCD to get access to the reset switch. The upper shield has a flexible metal tab attached in the reset switch area. It appears to me that the function of the reset switch is to ground the upper shield to the system board below it by the use of the point of a pen to short the tab to the board. Since the tab was not touching the board below it, I assume that the reset switch cannot be the cause of NO power to the unit. Please let me know if there’s a flaw in my reasoning or how the reset switch operates."

Is my assumption correct?

You could always test the switch. An ohmmeter with a continuity mode is the usual tool for that job. Then you'd know if it's stuck or not.

The reset switch isn't really a switch in the normal sense. The upper metal shield under the keyboard has a flexible metal tab attached to it in the area of the reset switch. The directions call out to insert the tip of a pen into the opening of the reset switch if the system locks up. It appears to me that this action would ground the metal shield to the system board below it. In my case, the tab was not touching the board below it, therefore I assume that the reset switch cannot be the cause of NO power to my unit (I did check for continuity with a meter).

Since I haven't found a problem in any of the more obvious areas, I must conclude that the system board must be the culprit. What's frustrating is that typically when you have no power in typical electrical appliences, the cause for NO POWER is usually the easiest to identify and fix.... guess not in computers. Thanks for all your comments and suggestions.

Your hardware maintenance manual should have a power system checkout.

770 Power Checkout, page 533 in the book I have.

If you look around on IBM's suport site or do a Google search, you should be able to find the latest copy of the Hardware Maintenence Manual for your laptop computer.

Also, have you checked your AC adaptor with a voltmeter?

I have verified that the AC power supply has the proper output voltage. I also downloaded the Hardware Maintenence Manual (Jan 99; S10L-9621-02; 136 pgs). Since I cannot charge a battery I can only use the AC power supply. The troubleshooting process leads me to "Undetermined Problems". In this circumstance, you should remove the DIMM, hard disk drive, PC card, battery pack, any external devices, etc., and then plug in the AC to see if it powers up. I haven't done this, but since I don't have any of the LED's lighting up while using the AC power supply, does it make sense for me to remove all these components? Would you guys suggest that I try that?

Well, you have nothing to lose. I tried the same thing as wel as everything else in the book on the dead 600E I used to own and to no avail, but still, I'd give it a try anyways. There's nothing to lose in doing this.

I'll give it a shot after I get back from a volleyball tournament this weekend. Thanks.

Also,can't believe nobody mentioned this.....make sure the little switch that the LCD depresses when you close the LCD is not stuck down or no good....if so it would keep the machine from waking up....

And yes,if you have a dead laptop,the first thing to try is remove EVERYTHING you can...HD,CD,Memory,Etc.....then if it does boot,start adding the parts back in one at a time until it dies again ,and then you know what part is the culprit..!!!

Good Luck....

Later...

Greg St.L

The lid closure switch would not likely cause this problem. On the 600X anyway, which is just a little later vintage, the machine can be turned on and used just fine with the lid closed... with an external keyboard, mouse and monitor.

Even my 750P will at least attempt to start with the lid closed, then it immediately suspends before the OS starts.

I’m back and will make another run at this dead unit. There is no sticking lid switch that I can see. Matter of fact, I don’t even see anything that resembles a switch…. The latching mechanism moves freely and doesn’t appear to activate any power switch.

I’ve also run into a problem trying to remove the upper shield. The picture in the manual I downloaded (Hardware Maintenance Manual Jan 99; S10L-9621-02; 136 pgs), doesn’t match with my unit… as far as to the location of the screws and their accessibility. Does anyone have a later or different version of the manual they can provide me? Thanks.

That's the right manual you've got. That's the same one I have used to open up my 770Z and 770E. I found the diagrams accurate for my machines, including the information about getting past the keyboard and heat shield.

Phil.

JD.

I would do absolutely anything, to wake a ThinkPad 770Z back to life.

1½ year ago, I bought a dead 770, that wouldn't do anything.
It turned out, that the CPU-card had pulled itself out from the slot, due to thermic reasons.

Reseating the CPU-card brought the 770 back to life, and it's still alive.

It may be, that the 770 uses CPU-cards of the MMC-1 formfactor, and the 770Z uses the MMC-2 formfactor, but with that experience in mind, I would definately try reseating the CPU-card.

If that doesn't help right away, then try reseating it one or two times.

If that doesn't help either, then disassemble the machine completely and clean up the slots and contacts.

Assemble it again.

BTW.
When you have the machine in parts, then take out the 64 MB module, that sits in the third, and normally unreachable, memoryslot.
It could be defective.
The slot can be ignored, since it shares banks with one of the other two user-upgradeable memoryslots.

Good luck

Kindest regards
Brian

Thanks to all of you who have responded. I've got the unit apart and will check for any obvious defects before I reassemble it and hope for the best.