820-00165 fan spins, flashing folder, tried good SSDs, not seen by diskutil

[Outofwhack]

Initially no fan spin, 33mA draw and very clean board except slight corrosion around R7611, cleaned up and got fan spin but left with flashing folder.

pp3v42_g3h 3.4v
ppbusg3h. 8.9v

draws 780mA

pp5v_s5 5.09v
pp5v_s0 5.3v


ssd_pwr_en 3.3v
smc_pwrfail_warn_l 0v
ssd_pcie_sel_l 0v
smc_oobi1_r2d_conn_l 3.3v
smc_oobi_d2r_conn_l 3.3v
p1v05_s0_vref 1.8v
p1v05s0_fb 1.05v
pp1v05_s0 1.05
ssd_reset_l 3.3v
ssd_clkreq_l 0v
ssd_clkreq_conn_l 0v
pp3v3ssd_vmon 1.02v
ssd_reset_conn_l 3.3v

U3740 OR-gate seems suspect to me with OR -gate input pins 6 at 3.3v and pin7 at 0v and output pin 8 at 0v (but another 00165 board I have gives same result)

I can boot from high Sierra or El Capitan install media on USB drive but cannot see internal SSD in disk util.

Any ideas?

 

[2informaticos]

"U3740 OR-gate seems suspect to me with OR -gate input pins 6 at 3.3v and pin7 at 0v and output pin 8 at 0v (but another 00165 board I have gives same result)"
Zoom in the pdf and look at OR gate input corresponding to pin 6...

"smc_pwrfail_warn_l 0v"
Can you compare with good board?
I expect 0V to mean failure; signal name ends in "_L".

Possibly corroded traces, or components related with SSD connector.

 

[Outofwhack]

smc_pwrfail_warn_l is also 0v on another board I have so I think I will assume this is normal.

Wow well spotted, after I zoomed to 800% I can see the negation!

 

[2informaticos]

Compare diode mode to ground on all SSD lines, with good board.
Do it with the same SSD connected in both.
Don't forget to check on both side of C3710-17 and U3710/11 data pines.

 

[2informaticos]

Once external monitor is detected, external video is enabled.

 

[Outofwhack]

Will the external monitor be detected if the OS is not booted?

 

[2informaticos]

The connector has hot plug detect capability (HPD) for display port.
Detection is done by hardware.