Hi i've THINKPAD T450S - NM-A301 with no power when i diagnosed it i'm only getting 20v on the main power nothing else on U41 chip that generate 5v and 3v i only get 20v on VIN pin and 0v on EN, EN1 and EN2 pins when i check the schematic EN, EN1 and EN2 signals comes from SIO chip and there's no 3,3v around SIO chip there's only 20v on pin 65 that's. Is the SIO chip dead? please help
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Re: THINKPAD T450S - NM-A301 no power
What do you have on pin 22,29,2?
You need the ic to generate vreg3 and vreg5 before talking about en1 and en2 -
Re: THINKPAD T450S - NM-A301 no power
Hi on U41 Chip on Pin 2 = 0v. Pin 22 = 3.3v. Pin 29 = 0vComment
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Re: THINKPAD T450S - NM-A301 no power
Remove all power. Meter in resistance mode (2k scale).
Measure the resistance to ground of VREG5 (pin 29) of U41.
Post the readings.
VREG5 will only enable if EN (U41, pin 12) is a logic HIGH.
EN (pin 12) of U41 receives this signal from the TQFP128 (Toshiba) part TB62D516FG (TQFP128 14X14) @ U101 (pin 96) = KBC ??Attached FilesComment
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Re: THINKPAD T450S - NM-A301 no power
This should not be the diode mode setting. Suggest the 2k ohm scale (or closest on your meter).VREG5 Pin 29 = 0.451 resistance to ground
Can you confirm the resistance scale used for this measurement ?Comment
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Re: THINKPAD T450S - NM-A301 no power
The rather high resistance is ok and confirms there is no excessive load (ie. short circuit or a bad cap) on this rail. So this rail has no reason to turn OFF.
Now for this rail to enable, the EN pin of U41 needs to be a logic high as per the shared datasheet for this component.
This logic level for the EN pin comes upstream from the Toshiba component (pin 96).
Is the Toshiba component warm / hot to the touch ? Review if the power rails are present on this component.Comment
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The screen seems to blackout and stay black, but with a flashlight I can see the display.
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Assuming... -
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