One thing I observed was that if the USER button is not pressed, the
40W printing took some time (indicating that CPU was trying to find
some boot code in NAND) and when the USER button was pressed while
resetting the 40W was being printed immediately. This indicated that
SD card is not being detected by the CPU so I further did some
hardware testing and found some things as below:
1. There is no supply voltage (3V) at the SD card connector pins.
2. SD DET pin shows something about 0.7V when SD card is not inserted
and goes to 0V when inserted. The 0V is expected as it shorts the pin
to ground when card is inserted but when the card is not inserted, it
is pulled up to 1.8V. So I further checked some voltages at the test
points as per schematic.
3. Voltages found to be in line with specifications are:
VBAT = 4.14V
VDD1 = 1.2V
VDD2 = 1.2V
VDD_PLL1 = 1.8V
3.3V rail = 3.27V
4. Following voltages showed some errors:
VDAC_1V8 = 0V
VDD_PLL2 = 0.2V
VDD_SIM = 0V
VMMC1 = 0V
VIO_1V8 = 1.0V
5. Voltage across J2 is observed to be 0.1V indicating current draw of
1A. I doubt this is normal value?
6. Also the board heats up little more I guess. Since I do not have
any comparison board, I can not say this heating is regular or not,
but based on the voltage errors as observed above, it seems there is
some hardware problem occurred.
Probably, due to overcurrent, some LDOs are operating in protected
mode and hence their outputs are being shut down.
On Sep 22, 10:09 am, Maxim Podbereznyy <
lisar...@gmail.com> wrote:
> just check for 3V at the respective pin at the SD connector
>
> 2011/9/22 Gopal <
gopal.amle...@gmail.com>: