Managed to get a dead T20 live again...

[Msmax]

Tried today to get a dead ThinkPad T20 Mainboard, which had the "Blink of Dead" problem, back to live again.

All the prevous tricks with batteries and repeatedly pressing the On/Off button did not work with this mainboard any more.

I measured the voltage levels of the Power Converter IC and found it to be in a Shut-Off mode all the time, with or without battery. I do not know yet what is the cause of the regulator to be in this state, need further investigation.

Bypassing this security feature with a resistor did bring the mainboard back to live immediately. It started and booted till the red message displaying that no harddisk was found.
Note: This mainboard has never booted before as long I had it. I had bought it defect "as-is" from Ebay.

The next when I pressed enter to continue the unit died. If I switch it on now then the "ON" LED will come up but no display anymore.
Before the bypass only the harddisk and battery LED would blink for a second.

Not sure what went wrong. Maybe the resistor leads shorted to GND some where. Will check this tomorrow again.

For now I need some notebooks which suddenly do not boot anymore for my testing. Mainboards only are welcome, but will pay for complete T22 machines with this problem. Just need a few to compare (and if I get it a live again then I will have some nice working notebooks!).

Your help is appreciated. Get rid of those boards which is of no use for you lying on the shelf for years... need you help now!

Thanks, Msmax

[dsigma6]

You'll probably want to post in the marketplace so everyone sees this. Your troubleshooting should stay here so that it can be expanded, but yea...

[Dark Savant0]

I need to check back here more often...

Could you post picks of what you did and where you applied your solder? I have a dead T20 that I want back alive (mainly because it would be a better machine than all these random Porteges I picked up, plus it actually has a dvd drive) and if any advances can be gained from your experience, that would be great.

Thanks.

[Msmax]

Hello D,

If you have a multimeter then you can easily find out if the ADP3421 is causing problems.

Measure the voltage level on pin 17. This should read normally between 4V-5V. If it is zero then probably the ADP3421 is in shut-off mode. If you read the right voltage here then your problem is not related to the Vcore voltage of the processor.

If it detects an undervoltage in the 16V or 3,3V power supply line then the ADP3421 goes into this mode and pulls pin 17 to ground, reading 0 volt if measured with a voltmeter.

I checked both supply lines with the scope and both are ok on my machine. I do not know yet why it goes into this mode. I suspect the ADP3421 has problems with aging. Will try to find a new one and replace it to make sure.

If you carefully lift pin 17 from the PCB pad, then you can apply here a voltage level of about 5V through a resistor of ~220 Ohms.

Press the Power button and the machine lives again.

If any one has some more info on component level of troubleshooting then please share your findings.

Regards, Msmax

[rkawakami]

Msmax,

Hmm... maybe there's one of those AD chips on my T22. If I get some time this weekend, I'll pull it apart and look.

I assume you've checked pin 15 (SD/) and made sure it's not low? And how about the capacitors on pins 18 and 19?

[Msmax]

Hello Ray,

Pin 15 is always low if not powered up.
Point is that the /SD will be brought to 3.3 volt level if the power button is pressed, but the ADP3421 will not switch the output to generate the Vcore because it already is in shutt-off mode. Note: the power button is not directly wired to the /SD pin. The /SD signal is generated via other components on the board, but it is not relevant for this problem.

For my above described test, pin 17 should read between 4V-5V in the next setup:
- keyboard removed
- power supply plugged in
- battery removed

This level of 4V-5V is generated with a resistor divider circuit from the 16V power line. They are close to the right side of the chip, just below 2 capacitors.

I'm 100% sure there is an ADP3421 on all the T2x mainboards.
There is also an ADP3410, but this is just a FET switcher.

I will have a look at those capacitors.

Regards, Msmax

[Gerry Arsabuk]

Hi Fellows
MSMAX, did you make any advance in the problem? my machine with the same problem, i tested pin 17 of ADP3421 and it has 2.4 , V . Also tested pin 24 (Vcc) and is 0V.

I read a thread in other forum written by " GLYN" refering to the eprom 24RF08
http://xml.hardwareanalysis.com/feed/topic/28867/

i repeat, i do have 2.4 V at pin 17...should be eenough to power up? or MUST be between 4 and 5 VOLTS ???

thanks
Gerry