Apple MacBook Pro A1229, 17 inch, 820-2132-A Half fan spin problem

Hi
I have an A1229, 17" model,
Board code is 820-2132-A

This machine does not auto power on so I plugged in charger and touched the
power on pads with tweezers and got green light

The fan spins and stops, It keep on doing this
It is about 2-3 seconds from when fan starts to spin and stops


I get 5v, PP5V_S5 on pin 1 on u7300 and c8900

I checked all_sys_pwrgd, on Pin 4 of u7880 and get 3.2v

On c1252 which is PPVCORE_S0_CPU i get 0,7v

If I keep My probe on c1252 and when the fan starts I get 0.7v but then
when fan stops the voltage goes down to 0v but when fan starts spinning
again the voltage goes to 0.7v

This just loops

I tested resistors surrounding u7900 (ISL6255AHRZ)

I have checked R7905 which is 18.1 ohm

R7906 is 2.4 ohms
R7904 is 000.2 ohms

i tested for shorts on PPVCORE_S0_CPU and got 0.4 ohms
I get 5v on the fan connector also

I cant see anything wrong visually


Can someone please help
Thanks

Please heat up the GPU core using a hot air gun (200°C, 10-15 secs) and see if the MLB will fire up. If YES, GPU chip needs to be replaced. If NO, we will continue with diagnostics.

Hi
Thanks for the reply
I did heat up the gpu but it did not turn on
If it was a gpu problem, I would get a black screen

It should at least turn on and the fan should spin continuously rather than starting and stopping

beezjuice ha scritto:If it was a gpu problem, I would get a black screen

Not always. Short circuit on GPU power rails gives the same symptoms. Please measure the voltage and resistances to ground on all SMPS coils.

I have tested the s0 rails for ohms
and they are below
PP5V_S0 2.245k ohm
PPVCORE_S0_CPU 0.5 ohm
PPVCORE_S0_NB_GFX 42.1 ohm
PP3V3_S0 0.7k ohm
PP1V8_S0 1.3k ohm
PP1V5_S0 462 ohm
PP1V25_S0 130 ohm
PP1V05_S0 26.3 ohm
PPVCORE_S0_NB_R 26.1 ohm
PP0V9_S0 1.4k ohm

beezjuice ha scritto:PPVCORE_S0_CPU 0.5 ohm

Too low resistance, it means CPU may be faulty.

Tested on another board cpu resistance is the same

beezjuice ha scritto:Tested on another board cpu resistance is the same

What is your CPU model? I have the same A1229 with the same MLB and T7700 CPU. It is 100% working and the resistance to ground on both L7100 and L7101 inductors is 11Ω. Check the resistance of multimeter cables by shorting the probes.

Hi
I will check and report back
I have just noticed that the flex flat cable that goes from the I/O board was weak because of the pins coming loose from the pads and consequently ripping three pads which are not ground or not connected
I am trying to find a replacement

When I was testing for voltage, the magsafe light caught my attention
It was on steady but flickering so slightly as though the connection is loose, now i know why

I am just wondering is this the cause to why it is not turning on

--- Posts merged ---

Can you tell me what the resistance is for you on PPVCORE_S0_NB_GFX, please

--- Posts merged ---

My cpu is T7800
When I short My multimeter leads, My reading 000.3 ohms
I put one multimeter leads on ground and other on pin 2 on the coil and get the following
L7100 is 0.5 ohm
L7101 is also 0.5 ohm

I also measured these on another board which is dead and they are both 2.9 ohms

beezjuice ha scritto:I am just wondering is this the cause to why it is not turning on (...) now i know why

You did not specify what is the actual problem with your MagSafe connector so we cannot say anything about that.

beezjuice ha scritto:Can you tell me what the resistance is for you on PPVCORE_S0_NB_GFX, please

121,4Ω.

beezjuice ha scritto:My cpu is T7800
When I short My multimeter leads, My reading 000.3 ohms

So the actual resistance to ground on L7100 and L7101 is about 0.2Ω, which is way too low. Please desolder L7100 and L7101 and check whether that low resistance appears on CPU side pad or on the opposite pad. If it's on CPU side, most likely your CPU is short. If opposite, one of switching transistors may be short.

beezjuice ha scritto:I also measured these on another board which is dead and they are both 2.9 ohms

This is more probable resistance for T7800 CPU. I cannot compare as I have T7700 on my MLB.

Vogelek23 ha scritto:

beezjuice ha scritto:I am just wondering is this the cause to why it is not turning on (...) now i know why

You did not specify what is the actual problem with your MagSafe connector so we cannot say anything about that.

The problem is that the flat flex cable that goes from the left io board to motherboard has its pins coming off the cable, and now has a few ripped pads. I am trying to find a replacement part
I think it was working just by the pins making a slight connection to get the green light but sometimes it would randomly go off.
Also noticed sometimes the light on the magsafe charger used to flickr slightly as thought the connection was not right some where
but then the flat flex cable caught my eye

Vogelek23 ha scritto:

beezjuice ha scritto:Can you tell me what the resistance is for you on PPVCORE_S0_NB_GFX, please

121,4Ω.

Mine is lower, does that mean the gpu is broken

Vogelek23 ha scritto:

beezjuice ha scritto:My cpu is T7800
When I short My multimeter leads, My reading 000.3 ohms

So the actual resistance to ground on L7100 and L7101 is about 0.2Ω, which is way too low. Please desolder L7100 and L7101 and check whether that low resistance appears on CPU side pad or on the opposite pad. If it's on CPU side, most likely your CPU is short. If opposite, one of switching transistors may be short.

Does that mean my cpu is broken also

Vogelek23 ha scritto:

beezjuice ha scritto:I also measured these on another board which is dead and they are both 2.9 ohms

This is more probable resistance for T7800 CPU. I cannot compare as I have T7700 on my MLB.

beezjuice ha scritto:Mine is lower, does that mean the gpu is broken

Please note that PPVCORE_S0_NB_GFX is not a discrete GPU chip power rail but northbridge integrated Intel graphics. But if you have an integrated GFX only (discrete GPU is not soldered), the resistance may be different, however, it shouldn't be lower than 40Ω.

beezjuice ha scritto:Does that mean my cpu is broken also

You have set your Service Level = 2, so what's the point to ask another question without doing what you have been advised? I have already said what needs to be checked in order to determine where is the problem, but you have ignored that (or at least did not share any results). Please don't expect any further help if you are not going to do as advised. We are not a fortune tellers here and require some measurements results to go further with diagnosis, especially when it comes to such a complicated electronics like computer logic board.

Thanks for the reply
I am getting the measurements you asked
I was just asking your opinion

I was looking on the board view
L7100 pin 1 goes to IMVP6_PHASE1 and Pin 2 goes to PPVCORE_S0_CPU
I then looked at all the points it connects to regarding PPVCORE_S0_CPU
I saw that it connects to R1100
R1100 is 100 ohms but i measured mine and it is 000.4 ohms
could this be bringing the ohm reading down on L7100 and L7101

Please share the photo of this R1100 resistor as I cannot find it on the schematic.

Hi
Thanks for the reply
attached in where it is on schematic

Remove R7122 and R7123 and measure the value of R1100 again - if there is still a short circuit on it, CPU is faulty for sure. But if the measurement will show 100Ω, U7100 is faulty.

So Hi
L7100 , L7101 have been lifted

The short to ground is on the cpu side
L7100 pin 2 is 0.5 ohms

on L7101 pin 2 is 0.7 ohms