Counterparts to take over the morning’s board, said a Lenovo SL400 no CPU power, is the second revision board ah, I said trim see, good for you
Phone, get our hands on a look out pieces of burning there is no obvious place, I thought better to repair or supply, electric power measure the CPU
Pressure really did not come out, the measurement has several other large inductor voltage, MAX8770 has been replaced by the other side, do not worry again
Check to see if there blown down and welded up the problem, only rest assured that looked at the field with an oscilloscope control tube did not wave appears
, Had slowly checked to see if version number is rocky40, open the drawing as shown on page 80
First check the power supply 25pin and 19pin chips voltages are normal, the measured signal SHDN # 38pin open and found no voltage, SHDN #
Issued by the R8009 over from CPU_VRON measured resistance does not open, not in the measurement 38pin-to-ground short circuit, so it is obvious
How the other obstacles not found it? Heart feel pleased but should be repaired soon
Who is directly generated by tracing CPU_VRON, first look
Timing diagram is as follows,
To generate this signal CPU_VRON on the premise that ALL_SYSTEM_PWRGD first out of the signal, only ALL_SYSTEM_PWRGD produce
The EC will send CPU_VRON 99ms delay signal to the MAX8770 start the CPU power supply to open conditions, with ideas like, search
Drawings ALL_SYSTEM_PWRGD signal is generated the following circuit
This circuit is relatively simple needs of all the voltage is ok to send a set of PG signal here is not as long as there is a PG signal to the
Bit, ALL_SYSTEM_PWRGD signal will be to get low, measuring about R9201 power supply +3 VS normal, D9202 is normal for the first 1pin
There 3V, which has the following 3-way is only a, 1.05V_1.5V_PWRGD, DDR_PWRGD, VGA_1.1V_PWRGD, in this
Measurements and found several large inductor L8300 there is no voltage, memory voltage originally did not come out, U8300 will not be issued
DDR_PWRGD signal, repair nightmare has just begun here, Figure
Memory chip using a power supply TPS51116, 15PIN 5V 10PIN11PIN opening signals are 3.3V, the external circuit is also normal,
No apparent short-circuit, but the reference VTTREF 5PIN voltage has not, the chip does not work, leading to 1.8V output voltage
, They begin to suspect that the chip is broken, replaced chip failure remains, MOS tube and no damage, repairs into a deadlock, in the Forum Search
See if there can refer to the Lie Zi, found to have the same trouble but does not address, halo! Only slowly on its own investigation, and to open
Before replacement of suspect components, found a similar plate first 5PIN replace capacitor C8306, failure remains the same, then changed again
22PIN capacitor C8303, or, as in an instant with the oscilloscope measurements 21pin power of DRVH did not wave, it is not
Other way had one foot in front of a TPS51116 IC chip measuring whether there is any short circuit, when measured 23pin found this
To infinity, the measure does not pass 23pin to the inductor L8300 to see the schematic should pass, in the measurement of two-side infinite inductance, halo
Ah ~ inductors met ah bad the first time, the replacement of the inductor, power current floating up, and Lenovo ThinkPad’s LOGO appeared,
Troubleshooting, a little do not understand why the open circuit inductance instantaneous power measurement with an oscilloscope waveform does not control the class? 5PIN voltage reference VTTREF how it has not been produced? Your fingers a little higher Thank you!
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