820-3115 green light no boot no fan spin ppbus_g3h 4v

[gadgetfix]

hey all i got a machine it got green light no fan spin but the ppbus_g3h measuring low 4.10v?
pp3v42_g3h is good 3.4v

no sign of water damage
what can cause this?

 

[2informaticos]

Start measuring resistance between pins 17/18 and 27/28 at U7000.
If didn't solve, post voltages for U7000 (basic pins).

 

[JohnB8812]

Yep exactly what 2informaticos said probably current sensing

 

[gadgetfix]

u7000 17/18 27/28 both 0 resistance

 

[2informaticos]

Did you check on 200 ohms scale?
You should get 2-3 ohms at 17/18 and 20 ohms at 27/28...
If good, post voltages for pins 2, 3, 9, 15, 19, 20.

 

[gadgetfix]

on 200 ohm scale, I get 3.5 ohms on 17/18 and around 20 ohm on 27/28

 

[gadgetfix]

voltage on pins

2 - 16.8v
3 - 4v
9 - 0.02v
15 - 0.05v
19 - 5.10v
20 - 5.09v

 

[2informaticos]

Check if R/C7025 are there and good.

 

[gadgetfix]

both look good. what is the point of having a 0 ohm res?

 

[Paul Daniels]

0R resistors are more useful than one would initially think. They can be used as an additional layer on a board (letting you jump over traces), they can be used to let you enable/disable behaviours or isolate sections during testing / debugging, and they can sometimes be used as desperate-last-hope fuses.

 

[gadgetfix]

Thanks Paul

 

[JohnB8812]

With those measurements, this seems like a bad ISL6259. Is PPBUS shorted to ground? If so, find short. If not, replace ISL

 

[gadgetfix]

changed isl now fan spin green light ppbus 12.68v
i will check in machine and report back.

thanks john

 

[JohnB8812]

Awesome let us know how it goes! 12.68 seems a little high, so make sure it charges a battery properly and runs off of one.

 

[gadgetfix]

Awesome let us know how it goes! 12.68 seems a little high, so make sure it charges a battery properly and runs off of one.

Just curious why its good to run with battery? should boot with one without right? Anyways I threw it into a working case and no chime, no display. fan still spins. I put under thermal cam and u1800 seems a little hot. its around 60-70c I know the cpu's do get Real hot on these but not sure if this helps in anyway. Would there still be fan spins if CPU was not good?

 

[JohnB8812]

Yes will run without battery was assuming it might have been fixed. Light on a USB mouse lighting up? CPU Vcore present?

 

[gadgetfix]

1.11v measured on ppvcore_s0_cpu

 

[2informaticos]

When board really works, VCORE should drop around 0.8V.
Look if U2600 sends out 25MHz at pin9.
Check all traces and resistors around SPI chip U6100.
Also try new BIOS, with clean ME.
Check if R7403 is OK.

 

[gadgetfix]

everything look good cant check for pin 9 as i got no oscilloscope.

 

[2informaticos]

"everything look good"
Does this mean visual inspection only?
You must measure all the mentioned resistors.

Post at least what DC level get on pin 9.