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.

 

[Outofwhack]

Diode mode to ground on exposed pins 53 to 29 of SSD connector are similar between two boards using same SSD.
Pin53 to pin29 reading (dashes separate the pins) 0-.4-.4-0-OL-.4-.4-0-.4-.4-0-.4-.4-0-0-.4-.4-0-.4-.4-0-0-.04-.04-0
My other board had very similar values with only pin 52 varying slightly to 0.7v

Visual inspection of C3710-17 and U3710/11 are all clear of corrosion and chip VCC good. U3710 AND gate had 0.65 on both inputs and 0v on output.
U3711 AND gate had 3.3v on inputs and 3.3v on output

So still wondering where the problem is.
What is the purpose of signals SMC_OOB1_R2D_L and SMC_OOB1_D2R_L ?

BTW I know Ive asked this about iMacs but will all Apple notebooks when powered, fan spinning present video on their thunderbolt ports when the LCD is not connected?

 

[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.

 

[Outofwhack]

Diode mode to ground on exposed pins 53 to 29 of SSD connector are similar between two boards using same SSD.
Pin53 to pin29 reading (dashes separate the pins) 0-.4-.4-0-OL-.4-.4-0-.4-.4-0-.4-.4-0-0-.4-.4-0-.4-.4-0-0-.04-.04-0
My other board had very similar values with only pin 52 varying slightly to 0.7v

Visual inspection of C3710-17 and U3710/11 are all clear of corrosion and chip VCC good. U3710 AND gate had 0.65 on both inputs and 0v on output.
U3711 AND gate had 3.3v on inputs and 3.3v on output

So still wondering where the problem is.
What is the purpose of signals SMC_OOB1_R2D_L and SMC_OOB1_D2R_L ?

 

[2informaticos]

I bet for PCH internal damage.
R7611 is on the feedback loop for 1V05_S0.
If its value increases, output voltage goes high; an overvoltage occured, because of corrosion...