Dell Precision 7530 Dead

[mon2]

Continue to trace the active voltage onto PQ17 -> PQ18 and also PQ22 -> PQ23. Finally if each is enabled, there should be a voltage @ +SDC_IN.

[shybear]

Continue to trace the active voltage onto PQ17 -> PQ18 and also PQ22 -> PQ23. Finally if each is enabled, there should be a voltage @ +SDC_IN.

PQ 17/22 =>(1-2-3) 19,55V (4) 9,1V (5-6-7-8) 19,8V
PQ 18/23 => (1-2-3) 19,55V (4) 19,5V (5-6-7-8) 19,8V
If (5-6-7-8) voltage is detected on PQ17 / PQ18 on PQ22 / PQ23 is 0,3mV and viceversa. This depend in which usb-c is plugged power.
Searching on schematic @ +SDC_IN that should be 19,5V I get:

PR700 19,55V
PR706 (2) 19,55V
PQ700 => (1-2-3) 19,55V (4) 8,99V (5-6-7-8) 19,55V
PQ20 => (1) 19,55V (2) 9,6V (3) 19,55V
This last values are present always no matter what USB-c is used.

[shybear]

In these days I tried to looks for something wrong but no luck. Any other suggestion ?

[mon2]

Confirm the voltage of the RTC battery. This is a coin cell style of battery.

The Dell Precision 7530 uses a 3V CMOS/RTC battery, often with a 2-wire, 2-pin connector (e.g., NGRJG, 0GW0K9). It is located under the base cover, near the main battery, and typically requires removing the base cover and a securing screw to replace. This battery powers the system clock and BIOS settings, often failing with "System CMOS checksum bad" or "Time-of-day not set" errors.

Key Details for Replacement:

• Part Numbers: Often listed as compatible with part # NGRJG or generic 2-pin, 2-wire, 3V RTC batteries.
• Location: The RTC battery is located underneath the bottom base cover, specifically positioned near the main battery.
• Replacement Steps:
  1. Remove the seven base cover screws and remove the base cover.
  2. Disconnect the main battery connector.
  3. Locate the small, wrapped RTC coin cell battery (usually near the hard drive/palm rest area).
  4. Unplug the 2-pin connector from the motherboard, remove the old battery, and install the new one.
  5. Reassemble the base cover.
• Compatible Models: The same RTC battery often works with the 7510, 7520, 7540, 7710, 7720, 7730, and 7740.

[shybear]

Original RTC battery is 2,78V but just to be sure I tested it using a new working battery (3,27V) but mainboard doesn't power on.
Actually I'm testting mainboard keeeping all dismount and also video board dismounted.
Anyway I think the problem could be related on BIOS. On BIOS chip UC5 if power is connected I don't find 3,3V on pin 8 as expected and CH9 give me just 0,02 ohm.
ON PU100 PIN 16 & 17 I've 3,3,V.

[mon2]

What is the resistance to ground of +3.3V_SPI? It is 0R02 ohms? If shorted, inject 1 volt (max) onto this line. Who is heating up? If it is the PCH / CPU, game over. The +3.3V_SPI power rail is being shared by the PCH.

[shybear]

Bad news. As you said +3.3V_SPI to GND is 0R02 ohms and so inject a low voltage on it, current rise up at 2 - 2,5A . L ooking carefully with thermocamera its clear BGA chip UH1 overheat in a point. Just as last chance I removed CH9 but shorts is still present. Time to looks for an other mainboard.