[SOLVED]820-4924 - No Power.

[gcain]

Board came in with a dead keyboard, but I've never seen it power on.

Green / Orange light all good.

ppbus_g3h = 12.58
pp3v42_g3h = 3.433
pp5v_s5 = 5.02
pp5v_s0 = 0v
pp3v3_s5 = 3.344
pp3v3_s4 = 0
pp3v3_s3 = 300mV

 

[gcain]

P3V3S3_EN on U8010 missing.

U8010::1/3 = 300mV

PM_SLP_S4 is 0v.

 

[TCRScircuit]

So we need to restore PM_SLP_S4 L in order to get P3v3S3_EN. Look at page 64 of the schematic and check the resistors for S3 Enable. Included a pic of the resistors you need to check.

 

[TCRScircuit]

However, Since Pm_SLP_S4_L is missing, Those resistors are not likely the cause of the problem, but they need to be checked.... PM_SLP_S4_L comes from the CPU, But can't be generated if the CPU isn't on or if the clock signal is messed up. Check your clock circuit and see if you have Vcore.

 

[gcain]

PPVCOMP_S0_CPU = 0v.

Thanks for the info TCRS, I'll investigate why VCore is missing quickly.

 

[gcain]

If nothing above s4 is on, surely S0 won't be there?

 

[larossmann]

Does PM_SLP_S4_L turn on really quickly then go to 0 or is it 0 from the moment it is plugged in? Does this turn on when everything is disconnected from the machine? Dead keyboard means liquid somewhere, how does U1950 area look? Clock area? SMC area?

 

[dukefawks]

U6100 area termination resistors and traces suspect too

 

[gcain]

Does PM_SLP_S4_L turn on really quickly then go to 0 or is it 0 from the moment it is plugged in? Does this turn on when everything is disconnected from the machine? Dead keyboard means liquid somewhere, how does U1950 area look? Clock area? SMC area?

My DM doesn't pick up anything and I don't have a scope yet.

Board has never turned on for me, but the guy that received the job swears it was working.

U1950 looks spotless. The board as a whole is really really clean.

 

[gcain]

U6100 area termination resistors and traces suspect too

All resisters around U6100 look really and measure fine.

 

[TCRScircuit]

gcain Check your clock circuit.... If everything looks and measures ok leading to u1900, I would take the long shot and replace the chip... Takes 2 min and It will rule out the possibility of a bad clock chip...

 

[gcain]

The board performs an SMC reset just fine (light on charger flashes green, then orange again).

Inspecting clock circuit now.

 

[gcain]

dukefawks Should I replace the clock chip?
I'm reluctant to just replace random chips hoping for a result.

 

[Gurmon]

dukefawks Should I replace the clock chip?
I'm reluctant to just replace random chips hoping for a result.

without a scope you wont know if the 32khz signal is clean and stable. If you have another chip try it.

 

[gcain]

Tried to track down a scope again, but no dice.

Thanks Gurmon, will swap the clock chip and report back.


Oddly enough, the board booted (CPU got hot) once yesterday at random, but hasn't done so again.

 

[gcain]

Plugged another battery into the board and it boots up every time.

So it appears it will only boot when a good battery is connected. Trying to work out how come I didn't pick up on this.

Can someone suggest what would be wrong that it will only boot with a known good battery? Going to try work backwards to see how I missed this.

Luckily I hadn't started removing chips.

 

[Gurmon]

Fault will be around u7100. Is Q7180 opening ?

 

[dukefawks]

Since your PPBUS is fine at 12.6V it must be a one wire issue. Do you get a green then orange light?

 

[gcain]

Board only works if battery is connected.

Green/Orange light etc. all good.

 

[dukefawks]

Smc_adapter_en high? Checked current sense circuit around isl6259?