820-2915 green light no power pulsing rails

[Jay]

Howdy folks,

Building on another post: https://www.rossmanngroup.com/boards...ssing-pp3v3_s5

Same issue. Green light all G3H rails OK but at PP5V_S5 and down all I get is pulsing.

SMC_PM_G2_EN and S5_PWRGD pulsing.

SMC_PM_G2_EN does not pulse at Q7080 but does pulse everywhere else.

Also pulsing are:
- PP5V_SUS
- PP5V_S3
- PP5V_S0
- PP3V3_S4
- PP3V3_SUS

Replaced U7201, issue persists.
First time I see this, not sure where to go from here.

Power draw on PSU jumps from 0.008 to 0.036, occasional spike to 0.166 amps.

 

[dukefawks]

History? What does Q7080 have to do with SMC_PM_G2_EN? PPBUS voltage?

 

[Jay]

History unknown but doesn’t look like anyone has been in here before. Q7080 is also on that line according to the boardview so that’s where I also measured, is my bv messed up?

PPBUS at 18.5v, drawing from memory so if that’s not accurate I can re-messure later. Number looked right at time of measuring else I’d have made note of it.

 

[dukefawks]

Stop using the BV as a schematic. BV is only for reference when looking up stuff, verify on the schematic. PPBUS at 18V would be bad...check.

 

[Jay]

Noted.
PPBUS fluctuates rapidly between 12.04 and 12.6V

 

[dukefawks]

Check all rails for shorts. Check resistance between pins 17/18, 27/28 of u7000. Was the GPU messed with?

 

[Jay]

Resistance 17/18 = 2.6ohm, 27/28 = 20.3ohm. GPU has not been messed with from what I can tell.

PPBUS_G3H = 7.4 mega Ohm and dropping
PPVIN_S5 rails = 5.7 mega Ohm and dropping (keeping same value as PPBUS_G3H)
PPDCIN_G3H = 0.L
PP3V42_G3H = 12 kilo Ohm
PP5V_S5 = 093.5 kilo Ohm
PP5V_SUS = 073.8 kilo Ohm

 

[dukefawks]

There are a lot more power rails than that!