(347) 552-2258 [email protected]

A1286 2009 820-2523, chime, no image, getting hot

V

VinceLx

Member
Hello,

Here are the symptoms:
- green light on charger ok,
- fan spins ok
- chime ok
- red light on mouse ok
- nothing on display. Sometimes grey screen one second or two when booting, sometimes no. Sometimes it lights on a second time for one second, sometimes no.
- no video
- current around 1.5A at the beginning, then slowly growing, and after 2 minutes can reach 3A, then I stop. Fans are not increasing strangely. Board is quite hot.
If I remove the trackpad connector fans are running full speed, it gets hot but this time cut itself automatically around 2.5A after 5 minutes

I measured all the rails, all the voltages are ok, I cannot detect any lower voltage due to a partial short for example.
PPVCORE_S0_CPU: 1.14V before boot, 0.99V after

Any idea where to start? Can it be the CPU or MCP overheating? How to detect/confirm that?
 
2informaticos

2informaticos

Administrator
Staff member
Did you test external video?
If no image on internal LCD, no reason for searching backlight.
Change thermal paste and see if still turns off.
 
V

VinceLx

Member
With external video (and internal LCD disconnected): nothing, not even grey screen. (on the other hand I see grey screen and video on A1286 2012 board with internal LCD disconnected, but I don't know if A1286 2009 board behaves the same)
With thermal paste current continues to grow but much more slowly, it does not switch off alone after 10 minutes but current is high, 2A. Fans are running higher then.
 
2informaticos

2informaticos

Administrator
Staff member
"PPVCORE_S0_CPU: 1.14V before boot, 0.99V after"
Looks like board boots,
However, confirm if there exists USB activity all the time.
 
2informaticos

2informaticos

Administrator
Staff member
Most likely, as this chip is very old.
Steady mouse light doesn't confirm USB activity 100%.
Use OSX pendrive with Link LED; if flashes, then you have activity for sure...
 
V

VinceLx

Member
So many tricks... :)
So, when using a blinking pendrive with OSX: after the boot the LED stays switched on for 12 seconds, blinks once, stays on 12 seconds, then permanently blinks. I tested this pendrive on a working board, indeed the LED blinks just after the boot. I tested it on a board with bad BIOS chip, it stayed always off.
Question: how can you diagnose a bad CPU, MCP or GPU, from a bad BIOS chip/BIOS software?
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
This not exact science.
Several steps, testing different things.

Looks like yuo have USB activity, but only missing video.
This points to MCP, because of its age too.
You can try a het test on ut, but will not solved the problem.
As you cannot get new MCP chip, is not a good idea to continue...
 
V

VinceLx

Member
I tried heat test, about 10-15s at 180-200 degrees on the die: still no grey screen.

I did this test quickly without heatsink, just switch on, chime and see if there is backlight. Should I put the heatsink back and wait 45 seconds to see if there is a blinking folder, even without backlight?
 
D

dukefawks

Administrator
Disconnect battery indicator to eliminate SMC_LID problem, check SMC_LID too.

Is the backlight coming on and just no image or no backlight at all?
 
V

VinceLx

Member
The board is out of the case, SMC_LID: 3.3V
At the beginning sometimes there was a grey screen one second or two when booting, now nothing. No image also. LCD_PWR_EN: 0V
 
V

VinceLx

Member
I checked again LCD and cable, they work flawlessly with 2 other boards.
I will stop here with this board, I wanted to go as far as possible in finding the issue, it is not worth putting new stuff on it. It will become a donor board :)
 
V

VinceLx

Member
I am back with this one, thinking...
Assuming there is an issue in LCD connector: if I remove LCD connector, at least I should finally have external video?
 
You must log in or register to reply here.
Top