Hi,
I erroneously posted this request under general discussions. I apologize for any confusion and hope starting a new thread is okay.
I would greatly appreciate some help. I have three 2010 MacBook Pro 820-2850 boards that won't chime or boot resulting in black screen.
I have already replaced U7400 Q7410 on one board and U7000 and Q7030 on another.
Confirmed all traces, resistor values and solder connections associated with these buck converter circuits and replaced any that were bad.
Compared diode mode voltages on the buck converters with known good boards and all agree.
It appears that these circuits now appear to be operating correctly.
All of the following observations are without battery connected.
Get steady green charger light, steady fan spin and steady on sleep indicator LED.
Voltages look good and all power good signals and reset lines appear correct.
Reset SMC produces no change when board is installed in known good chassis.
USB mouse LED does NOT turn on.
Memory stick LED will light.
Measured 5 volts at USB connector.
PPBUS_G3Hot is 12.59V
With no RAM, get 1 beep.
No change when trying either RAM slot on its own.
No signs of corrosion.
GPU panic cap and thermal grease changed
Can force shutdown using power button on known good keyboard so that interface appears ok.
Battery indicator and charger LED work and PPBUS_G3HOT is adjusted to 12.59 so I assume SMC is ok.
CPU Vcore is about 1.1Volts.
Same symptoms with all cables (except trackpad) disconnected.
Don't know history of these boards as I bought these computers as is on eBay although one board had been previously worked on around the LCD backlight circuit.
I'm assuming getting 1 beep with no RAM means the EFI (BIOS) and CPU are both good but could someone please confirm that is a valid assumption or how to confirm they are good?
Any suggestions on how to proceed?
Thanks!
I erroneously posted this request under general discussions. I apologize for any confusion and hope starting a new thread is okay.
I would greatly appreciate some help. I have three 2010 MacBook Pro 820-2850 boards that won't chime or boot resulting in black screen.
I have already replaced U7400 Q7410 on one board and U7000 and Q7030 on another.
Confirmed all traces, resistor values and solder connections associated with these buck converter circuits and replaced any that were bad.
Compared diode mode voltages on the buck converters with known good boards and all agree.
It appears that these circuits now appear to be operating correctly.
All of the following observations are without battery connected.
Get steady green charger light, steady fan spin and steady on sleep indicator LED.
Voltages look good and all power good signals and reset lines appear correct.
Reset SMC produces no change when board is installed in known good chassis.
USB mouse LED does NOT turn on.
Memory stick LED will light.
Measured 5 volts at USB connector.
PPBUS_G3Hot is 12.59V
With no RAM, get 1 beep.
No change when trying either RAM slot on its own.
No signs of corrosion.
GPU panic cap and thermal grease changed
Can force shutdown using power button on known good keyboard so that interface appears ok.
Battery indicator and charger LED work and PPBUS_G3HOT is adjusted to 12.59 so I assume SMC is ok.
CPU Vcore is about 1.1Volts.
Same symptoms with all cables (except trackpad) disconnected.
Don't know history of these boards as I bought these computers as is on eBay although one board had been previously worked on around the LCD backlight circuit.
I'm assuming getting 1 beep with no RAM means the EFI (BIOS) and CPU are both good but could someone please confirm that is a valid assumption or how to confirm they are good?
Any suggestions on how to proceed?
Thanks!
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