Today i am going to explain you laptop VRM section because this section is very important section in motherboard. i explain you very simply.


Testing And Fault Finding VRM Section:- Laptop Repairing Institute

We are check the VRM Section when after on the power no display Generating Mother Board, CPU not Heat, so we are check VRM Section’s

  1. Check logic on TP1 point, received the logic on TP1 point but CPU is not normal heat proper, and then capacitor faulty of TP2 point or CPU faulty.
  2. If not receive the logic on TP1 point, and then check the input supply coming. On I gate mosfet drain point (P1to p.3.5v, P iv-12v). +ve supply on drain point, then check +ve signal or logic on mosfet gate. Logic is received but not received logic on IP1 point. Then check I gate, B gate mosfet for open.
  3. If +ve signal or logic not received on mosfet gate then +5volt supply check on Vrm Ic Vcc Pin. If supply is not coming then check the 0Ω resistance for open condition. If resistance open again and again then vrm Ic is faualty.
  4. +ve supply received on vcc pin and signal is not coming on I gate & B gate mosfet. So after that check shut down opposite signal on shutdown pin, high signal check on soft start pin, high enable signal check on enable pin, if low single received on SS(soft start) then check capacitor for shorting connect on this pin. After that shut down opposite signal is not received on shut down pin, so we are check in P-3 mother k Ω resistance, and in P.4 mother board check CPU section.
  5. If shut down signal, enable signal, SS soft start signal is ok, but signal not received on I gate and B gate pin, so after that in this condition Vrmc chip is faulty.
  6. After power on received the display, but CPU is hang. Check coil for short condition on IP1 point. Coil is ok then CPU is faulty.

Note: Any computer hand problem of virus, hardware, software, so in this condition , we are disconnect the hard disk with mother board,  if after disconnect the hard disk with mother board, already CPU is hand, the problem is  CPU or VM section. If after disconnect the hard disk CPU is not hang. Then problem is operating system, virus and bad sector in hard disk.

  1. After power on is received the display and system restart again and again, then change the capacitor for shorting on TP2 point.

Note: Restart problem is generate of virus or capacitor.

  1. System on-off again and again the start. So we are check capacitor on TP2 point.
  2. Mother board working with ATx SMPs but we are connect Apower supply of mother board display is not coming, and replace the capacitor of I gate mosfet drain point.

The working of this section is receive the supply 3.3v from SMPS, 2.5v from VRM section and working 14.318MHz  crystal after that provide to CPU free clock pulse of CPU. In this section use the clock generator IC. And 14.318MHz crystal of create the section. Clock generator IC coming many types of company’s. example: ICS, Max, window RI1, VIA etc.

Clock generator IC is a programmable IC. It is provide CPU free clock pulse to CPU according to received Bingryon Fs0to Fs2 pin.

Received the the supply clock generator and then IC osclliator section on received the +ve/-ve supply and provide to CPU free clock pulse to CPU. CPU is received the supply from VRM section and received the clock pulse from clock generator section, after that CPU is on and generate the reset signal for all mother board. It’s procedure is working of this types

  • Diagram of rest Sections:
  • Block Diagram of clock generator Section:
  • Description of clock generator block diagram:

1st clock generator IC received the +ve supply 3.3v from SMPS 2.5v from VRM section and –ve supply received from Gnd.

After that bingry received on Fs0 to Fs2 pin (frecouncy select pin) of clock gererator IC pins. It is working with 14.318MHz crystal and on. Start the working and provide the CPU free clock pulse according to CPU, provide the 29MHz to 75MHz. Clock pulse of RAM, 24.57MHz, 27MHz clock pulse of IEEE1394 section, 27 MHz, 48MHz of USBI.0, 2.0, 66.6 MHZ clock pulse of Pc I express slot, 66,100, 133MHz clock pulse of HDD/CDROM, 8MHz, 16MHz, clock pulse of ISA slot, 33.3MHz clock pulse of PCI slot, 54.54MHz & 74.17MHz clock pulse of N I SC/PAL/Encoder, 66MHz & 54MHz clock pulse of MPEG2, decoder, 66.6 MHz clock pulse of ICH and system control IC.

  • Testing and faultfinding of clock generator section:

We are check of this section when use on the power, no display in mother board and reset signal not received from CPU. CPU is not normal heat and then we are check clock generator sections:

  1. If reset signal is not coming but VRM section, CPU is ok then we are check free clock pulse on clock generator free clock pulse on pins, clock pulse is received but reset signal is not coming. Then clean CPU socket or change the CPU sockets.
  2. If not received clock on clock generator IC free clock pins, then check 2.5v, 3.5v unk Vcc pulse. VDD pins, if +ve supply is not coming from VRM, SMPS sections, then check the VRM and SMPS.
  3. If +ve and –ve supply is coming but received clock pulse on CPU free clock pins, then change the 14.318MHz crystal. If crystal is ok then clock IC is faulty.
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