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A1278 820-2936-B no image

H

hgoncalves

Active member
Hi.

I have an A1278 820-2936-B with no image.

Already tried known good display, but still no image.

J9000 voltages:
Pin 2/3 (PP3V3_LCDVDD_SW_F) = 0V
Pin 4 (PP3V3_S0_LCD_F) = 3.3V
Pin 22 (PPVOUT_SW_LCDBKLT) = 0V

PPBUS_S0_LCDBKLT_FUSED = 12.56V

Can you help?
 
H

hgoncalves

Active member
Hi.

Big mistake. Sorry...

Because it was consuming 0.600A on bench PSU, no big coil was shorted, and it had fan spin, I assume it was booting. Big error.

It has no USB activity, and CPU core coils have 0V and 0.012 on diode reading.
 
2informaticos

2informaticos

Administrator
Staff member
All the other coils have correct voltage?

Post U2850/60 voltages.
Check R7402 and traces for corrosion.
 
H

hgoncalves

Active member
Yes, all coils have voltage, except L7550, L7510 and L7520 that have 0V.

U2850:
1= 3.3V
2= 0.046V
3= 0V
4= 0V
5= 3.3V

U2860:
1=0V
2=3.4V
3=0V
4=3.3V
5=0V

R7402 seams OK (90.5kohm), and her traces are good. however, on CPUIMVP_TON only has 0.555V, and on PPBUS_S5_HS_COMPUTING_ISNS has 12.53V (not sure if that's normal values)
 
2informaticos

2informaticos

Administrator
Staff member
"4=3.3V
5=0V"
I bet for inverted readings there.

Check all SPI Bus Series Termination resistors and their traces.
Try known good BIOS, clean ME.
 
H

hgoncalves

Active member
You're right, sorry.
U2860:
4=0V
5=3.3V

All SPI Bus Series Termination resistors and their traces are OK.

Can you please share a clean ME?
 
H

hgoncalves

Active member
TKS.

After flashing the BIOS, It powerd on 2 or 3 times, but now it doesn't power on again. However, now I only have 0V on L7550. All other coils have voltages but no USB activity nither image.
 
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