Lenovo NM-C421 partial RTCVCC short

[reparetech]

Hi, I seem to have a partial short on the VCC3SW circuit coming from RTCVCC.

• VCC3SW initially measures about 1.1V.
  
• RTCVCC to ground measures approximately 9 ohms, but it does seem to fluctuate as I have measured it at 2 ohms.
  
• There is no apparent water damage (or any other damage) on the board.
  
• Removing PD0001 disconnects RTCVCC from VCC3SW and VCC3SW is back to 3.3V.
  
• R1301 measures about 1M measured directly on board
  
• C1608 and C1609 have been removed.
  
• There is no CMOS battery connected.
  
• C2001 is a no stuff.
  
• R2002 and R2003 have both been removed.

There is still a short on RTCVCC.


Am I to assume the partial short is coming from the CPU, or am I missing something ?

Thank you very much !

[mcplslg123]

Re: Lenovo NM-C421 partial RTCVCC short

Remove C1201/1204/1612/2002/2003. If its still showing low resistance, Rtc Section of PCh is definitely shorted.

[reparetech]

Re: Lenovo NM-C421 partial RTCVCC short

Remove C1201/1204/1612/2002/2003. If its still showing low resistance, Rtc Section of PCh is definitely shorted.

Thank you very much, this is exactly why I asked on this forum, I never would have thought to check the other circuits related to the RTC.

Unfortunately, the short is still present, so I'll call this one dead.

Thanks again !

[mcplslg123]

Re: Lenovo NM-C421 partial RTCVCC short

Yeh, This is very common fault speacially on SOC boards.

[Th3_uN1Qu3]

Re: Lenovo NM-C421 partial RTCVCC short

Didn't even get to read the whole title and my money was already on shorted PCH section of CPU/SoC... sorry.