laptop toshiba p200D - Page 1
Forum section: electronics / repair

author: freebil
author_rank: Regular Contributor
timestamp: July 21, 2016, 01:13:01 pm
content: Hello. I bought a multimeter and I have a laptop that when I press to start it does not turn on. The blue led shows that there is voltage. Moreover multimeter shows that power supply output has 19.1V. I would like some advice about how to start. I am totally new to this. Here are some photos of the laptop motherboard. The first 4 are from one side and the last from the other side.

author: singapol
author_rank: Frequent Contributor
timestamp: July 22, 2016, 12:47:47 am
content: UT139C is a good multimeter,congratulations. Power supply at 19 V means power is good. Please check cmos battery voltage, it's the round silver coin disc inside the blue round socket at the left corner near blue led. Is it still 3V or dead/flat? Some system will not start if this battery is dead.

author: amyk
author_rank: Super Contributor
timestamp: July 23, 2016, 10:33:25 am
content: That's a Compal board. Googling "Compal JASAA" gets you a schematic.

author: poot36
author_rank: Frequent Contributor
timestamp: July 24, 2016, 06:00:21 am
content: Good work on eliminating the power supply as the problem. I would first start by checking that the power switch has voltage. Put the negative probe on the metal shell of any of the USB connectors and probe all the pins of the power switch with the positive probe with the laptop plugged in. You should get anywhere from 5V to 1.8V on the switch. If you do press the switch and see if the reading goes to zero volts. If it does the switch is good. Does it charge the battery? Also unplug everything that you can from the motherboard except for the power jack, power switch, and cpu to eliminate a short in another component.

author: wblock
author_rank: Regular Contributor
timestamp: July 24, 2016, 11:13:27 am
content: Is that liquid damage at the bottom of the first picture?

author: poot36
author_rank: Frequent Contributor
timestamp: July 29, 2016, 03:52:35 am
content: All of the white looking residue is from the stupid plastic covers glued to the motherboard for who knows what reason. There is no liquid damage that I can see. Is there power going to the power switch?

author: freebil
author_rank: Regular Contributor
timestamp: August 02, 2016, 07:42:14 pm
content: Thanks for the answers and sorry for the delay.1.) The voltages in power switch arepin1: 0Vpin2: 1.2Vpin3: 3.3vpin4: 3.3Vpin5: 3.3Vpin6: 3.3Vpin7: 17.3Vpin8: 0Vpin9: 17.3Vpin10:17.3VWhen I press the power button all 17.3 voltages go to 0V.2.) There is no liquid damage. It is glue as @poot36 said!3.) It cant charge the battery. When I have the battery on the motherboard and I plug in, an orange led flashes. So, I removed the battery.Any help is appreciated!

author: poot36
author_rank: Frequent Contributor
timestamp: August 02, 2016, 11:00:41 pm
content: If there is close to the adapter voltage going to the power switch the motherboard is most likely dead. The power switch is usually controlled by the keyboard controller chip and if that is not receiving the correct voltages nothing will work. Here is the link to the schematic:http://kythuatphancung.vn/uploads/download/8b839_Compal_LA-3831P.pdfTry and find the 5V and 3.3V standby voltages. On page 31 of the pdf you will find the keyboard controller chip. You should measure 3.3V on pins 9,22,33,96,111,125, and 67. If not you will have to troubleshoot the standby voltages shown on page 40. I have seen a dell motherboard with a similar fault that would start the standby voltages for a few seconds and then have them shut down so connect your probes then apply power to the laptop. Also take out the dedicated GPU if this model has one as a fault in in can cause this problem. Good luck.

author: freebil
author_rank: Regular Contributor
timestamp: August 13, 2016, 04:17:10 pm
content: Quote from: poot36 on August 02, 2016, 11:00:41 pmThank you very much for the info but I cant find the controller chip on the mainboard. Could you please check the photos and tell me where is? Thanks

author: NottheDan
author_rank: Frequent Contributor
timestamp: August 13, 2016, 05:09:16 pm
content: Quote from: freebil on August 02, 2016, 07:42:14 pmThat's an error code, indicating the nature of the fault. Take a note of which LED it is and the flashing pattern, then try to find someone with access to the maintenance manuals to tell you what it says.

author: poot36
author_rank: Frequent Contributor
timestamp: August 13, 2016, 06:09:41 pm
content: I cant see the controller chip on any of you photos so I presume that it is under the graphics card due to where the keyboard connector is located. The chip will have the markings ene KB926QFA1 on it. If this chip is not working properly nothing will work.

author: freebil
author_rank: Regular Contributor
timestamp: August 13, 2016, 07:19:32 pm
content: Quote from: NottheDan on August 13, 2016, 05:09:16 pmThanks for the answer. Some time ago it was flasing with pattern, but now it is flashing one time and it turns off. So, there is no any pattern.Quote from: poot36 on August 02, 2016, 11:00:41 pmThanks for the answers! All these voltages are 3.3V. Please help me with next steps if it is possible.

author: NottheDan
author_rank: Frequent Contributor
timestamp: August 13, 2016, 08:39:18 pm
content: Maybe the explanation here helps, maybe not:http://www.hardwareanalysis.com/content/topic/51345/

author: poot36
author_rank: Frequent Contributor
timestamp: August 14, 2016, 05:55:04 am
content: Ok that is good. The next thing to check is the 5V standby voltage shown on page 40 of the pdf. If you don't have that voltage then we will have to figure out why there is no voltage. If you do then that is good and we go back to the keyboard controller chip and find the pin that the power switch is connected to and see if the switch is correctly triggering it. If it is not then we have to figure out what is wrong with the switch part of the circuit. If it is correctly triggering then the fault could be the power detect circuit is not working that is also connected to the keyboard controller chip as well. If it is showing the correct input then the most likely fault is the keyboard controller chip itself and as this may be a programmable chip you cannot just go and replace it you have to get a pre programed chip or program it yourself. Have fun fixing the laptop and I hope you learn a lot about how a laptop powers up as a result.

author: freebil
author_rank: Regular Contributor
timestamp: August 16, 2016, 11:27:43 am
content: Quote from: poot36 on August 14, 2016, 05:55:04 amThank you! There is 5.145V voltage. So now, I am seeing page 31 and see if the power switch triggering correctly. But I am noob. How I can see this?

author: poot36
author_rank: Frequent Contributor
timestamp: August 17, 2016, 02:13:37 am
content: On pin 32 of the keyboard controller chip is the power button input to the chip. It should be at 3.3V when the power switch is not pressed and go to 0V when the switch is pressed. After further reading of the schematic it does look like you are supposed to get close to the adapter voltage on the power switch so that is good I guess. You can also try clearing the CMOS by shorting out the blue button cell battery for 10 seconds or so and see if that makes any difference.

author: Srbel
author_rank: Frequent Contributor
timestamp: August 17, 2016, 06:41:30 am
content: Quote from: poot36 on August 17, 2016, 02:13:37 amShorting the battery???

author: freebil
author_rank: Regular Contributor
timestamp: August 17, 2016, 07:40:38 am
content: Quote from: poot36 on August 17, 2016, 02:13:37 amThanks! The pin 32 has 3.3V and when I press the power btn it goes to 0.48V. Where to short the battery? Thanks again for your help!Moreover, in page 33, I see that the on/off btn connects to D13. The voltages for pin 1,2,3 are 17,28V , 3.3V and 17.63V. When I press the on/off btn the voltages go 0V, 4.77V, 0V.

author: Vietk123
author_rank: Contributor
timestamp: August 17, 2016, 05:58:40 pm
content: Just a quick question guys. Is this the same process of trouble shooting for all non power boards? Thanks for all the good info because it helps me learn more and more.

author: Srbel
author_rank: Frequent Contributor
timestamp: August 18, 2016, 06:27:27 am
content: Quote from: freebil on August 17, 2016, 07:40:38 amDon't short the battery. Short the 2 pins on the "Clear CMOS" jumper. Or take the coin cell battery out and put it back after 10 seconds.

author: Prehistoricman
author_rank: Regular Contributor
timestamp: August 18, 2016, 11:13:36 pm
content: Quote from: Vietk123 on August 17, 2016, 05:58:40 pmEssentially, yes. Find manuals. Check out errors. But always remember step 1 of troubleshooting: measure the voltage!

author: h.bashar
author_rank: Contributor
timestamp: August 18, 2016, 11:48:17 pm
content: Hi, don't want to bring your hopes down, but the big graphics card chip (the green BGA pacakge soldered on the MB), its solder joints tend to fail because of thermal recycling of the component , i.e when it gets hot and cool down the solder joints under it are mechanically stressed and may fail, if you exhaust all your options in power supply troubleshooting, this could be the problem and it will need to be reworked using a BGA rework station.Other thing to check is the LCD display inverter, not sure if you have checked that the laptop boots to an external monitor or not so give it a try and see how it goes.Keep up the good work as its a good learning experience.Best regards

author: poot36
author_rank: Frequent Contributor
timestamp: August 19, 2016, 03:28:19 am
content: This laptop has a soldered in rechargeable battery for the CMOS. Well there may be a clear CMOS jumper on a desktop most laptops do not have one. In this case though there is one labelled J4 on the motherboard. Find it and short it out for 10 seconds or so and see what happens. I would also check the POK line from the U6 chip on pins 11 and 30. If this is at 3.3V the power is ok and we can move on to the last standby voltage generated by chip U7 at 1.2V. You should get 1.2V from inductor L7 if not then there is a problem. If you don't get 3.3V from POK then the chip that supply's the 5V and 3.3V standby voltages does not think that they are in spec and shuts down to prevent damage to the laptop. The POK signal also turns on the 1.2V standby voltage. Also check pin 127 ACIN_R on the keyboard controller chip that it is at 3.3V and also pin 121 SYSON is at 3.3V. The ACIN_R indicates a valid power adapter is powering the system and the SYSON tells the rest of the computer to turn on all other voltage regulators and other various components.

author: Prehistoricman
author_rank: Regular Contributor
timestamp: August 19, 2016, 07:11:56 pm
content: Quote from: poot36 on August 19, 2016, 03:28:19 amSurely shorting it would damage the battery?

author: poot36
author_rank: Frequent Contributor
timestamp: August 20, 2016, 01:48:54 am
content: As this laptop has a dedicated CMOS clear jumper using it will not damage the battery. The battery in this circuit is protected by a high value resistor that prevents a high current flow out of the battery but grounds out the CMOS chip resetting it in the process.

author: Prehistoricman
author_rank: Regular Contributor
timestamp: August 20, 2016, 01:58:25 pm
content: Quote from: poot36 on August 20, 2016, 01:48:54 amOh, sorry, I misread your previous post.