Chuwi Lapbook SE not starting (x2) - Page 1
Forum section: electronics / repair

author: Iersuo
author_rank: Newbie
timestamp: December 20, 2019, 08:55:07 pm
content: Uhhh... Quite a story with these Chuwi laptops.Bought 2 Chuwi Lapbook SE laptops. Great laptop... Until it stops working all of a sudden.First one worked a week until it just shut off and never came back alive again. Locals said it was the CPU, but could not explain how they tested. One of these did not even disassemble the laptop. Just connected a charger (their own charger) and came back telling that it was the CPU. He might have also connected something to the HDMI port, but I saw only from far away, so not sure. After all of the local workshops had to send the motherboard to the Chuwi factory for repair. Already a full month there and no results. Even no replies... Ridiculous service.Anyways the issue now is that the second laptop has now done the same trick. This time worked about 4 months. Wow...Completely dead. Only power connector LED lights up and I can hear ticking sound from somewhere off the motherboard. Ticking sound only when power supply is connected.Then suddenly turned on after disconnecting the battery multiple times and trying to boot different ways. Turned on and worked for 5 more days perfectly (though only with charger connected, battery percentage always showing 0%). All of this time distinctive coil whine while working.After the 5 days, in the morning just not turning anymore and this time I think for good. Nothing helps.Decided to check the batteries from both of the laptops. 2 batteries tied together to create a higher voltage battery pack.Designated voltage: 7.6VMax power: 8.7VTeared off the tape a bit to get to the battery pack control board and the contact points. EXPECTED to measure 3.8V off each battery cell (Thus 3.8+3.8=7.6V), but multimeter only showing 2.8V off each cell.Measuring off the contact points from the battery pack to the motherboard, not really getting any values... From any of the black wires to any of the red wires - 0V.Only value I can get is when the charger is connected, I am getting 3V from the yellow wire to the red.Also one chip (power regulator I think?) gets hot very quickly as soon as the charger is connected.Any ideas where to look? Battery packs dead?Power regulator gone bad? Hard to distinguish, but might be the source of the ticking sound. Picture in attachments of the the hot chipMarkings:iTEIT8987E1833-BXSS162VBReally the intel CPU as they said? I always like to monitor temperatures in my laptop and CPU never gone over 75°C. Normal usage ~60°C. Would be weird to have 2 INTEL cpus dead so quickly

author: fzabkar
author_rank: Super Contributor
timestamp: December 20, 2019, 09:17:58 pm
content: IT8987E is an I/O chip (keyboard controller) and hardware monitor. Among other things, it monitors the state of the battery and drives the status LEDs. It is not a power regulator.See page 70 of the following document:s472165864.onlinehome.fr/anyware/manuels/N240PU_SM.pdf… or page 34 of this one:kythuatphancung.vn/uploads/download/c5ed7_Quanta_Y11C_dis_lay-vine_r1a_20140902_schematics.pdf… or page 84 of this one:www.e-weekly.co.uk/download/RnD/DRIVERS/CLEVO/W950LU/ESM.pdfpage 25:www.suamainlaptop.com/uploads/files/schematics/HP_X360_Y0D_PIKE_PV_VPRO_ELP4G_.pdfYou need to measure the voltages at each of the coils. If you can upload a detailed photo of the complete PCB, perhaps we could help you to locate the test points.

author: Iersuo
author_rank: Newbie
timestamp: December 20, 2019, 09:47:54 pm
content: The whole PCB. Upper left charging port. Lower right battery port unplugged.

author: Iersuo
author_rank: Newbie
timestamp: December 20, 2019, 09:49:38 pm
content: The PCB Divided into 4 parts.

author: fzabkar
author_rank: Super Contributor
timestamp: December 20, 2019, 10:02:24 pm
content: I can't make out any of the markings on any of the ICs. I suggest you measure the voltages at each of the coils, ie R22, R47, H2R2, 1R0, etc.If any voltage is absent, then check the enable pin of the corresponding regulator IC (or tell us its markings so that we can identify it for you). Also check the resistances between each coil and ground. That should tell us if any of the regulators are being overloaded.

author: Iersuo
author_rank: Newbie
timestamp: December 20, 2019, 10:07:53 pm
content: Ok will do that. Also found the diode on the upper left (right next to the power connector to be OL both ways.

author: fzabkar
author_rank: Super Contributor
timestamp: December 20, 2019, 10:18:47 pm
content: Is this diode in series with the external supply? If so, then that may explain why the battery is not being charged.

author: Iersuo
author_rank: Newbie
timestamp: December 20, 2019, 10:56:02 pm
content: How do I tell if it is in series?Will do voltage test tomorrow, but on quick check at least one coil gives very low and fluctuating voltage.

author: fzabkar
author_rank: Super Contributor
timestamp: December 21, 2019, 12:27:04 am
content: Which diode are you referring to?

author: Iersuo
author_rank: Newbie
timestamp: December 22, 2019, 10:39:48 am
content: Isn't a diode mark just next to the charging port? I thought that the part itself is maybe on the other side of the PCB? Sorry, maybe I am wrong.Anyways I measured all of the coils and results are in the pictures attached. 3 of them missing any voltage and the battery port only has 3V coming to one pin, thus the reason for the low charge of the battery?If these pictures are still not clear, point me where to take better pictures from.Thank you a lot for the input!

author: SaabFAN
author_rank: Frequent Contributor
timestamp: December 22, 2019, 11:42:38 am
content: Diodes next to the charging ports on Laptops are almost always TVS Protection diodes. Some have two diodes connected back to back inside the package while others contain just one diode.Are you sure that you measured the coils correctly? Hundreds of kOhms for a coil is extremely high. Would explain the problems, however (coils burned out).

author: Iersuo
author_rank: Newbie
timestamp: December 22, 2019, 11:47:13 am
content: Coils measured all to the chassis. All coils measured the same way and to all connection points.Also verified that I get 0 Ohms from chassis to battery connector's ground terminals.So I think the resistance measurement done correctly?

author: fzabkar
author_rank: Super Contributor
timestamp: December 22, 2019, 09:22:12 pm
content: There are several missing supplies (0V), but I can't find datasheets for any of the associated regulators. :-(It could be that the board is in standby mode, but I can't tell.The regulator with the 19 ohm load is probably VCCGI, and the one with a 273 ohm load is probably VDDQ. Both are sitting at 0V.Are there any ICs on the other side of the PCB?What are the voltages on pins 14, 15, 16, 30, 44 and 51 of the RT5077A PMIC?The functions of the SLP_Sn pins are defined in section 12.13 of the APW8858 datasheet.PMIC_EN controls VNN, V1P8A and V1P2A.SLP_S4 controls VPP_OUT and VDDQ.SLP_S3 controls VTT, VCCRAM and VCCGI.SLP_S0 controls VDDQ, VTT, VNN, VCCRAM and VCCGI.Edit:Here is an application diagram for the RT5077A PMIC:https://www.richtek.com/Products/Power%20Management%20IC/RT5077A?sc_lang=en&specid=RT5077ADatasheets and notes:RT9610C, Richtek, High Voltage Synchronous Rectified Buck MOSFET Driver for Notebook Computer, 5V, marking 2Qw, WDFN-8L:https://www.richtek.com/assets/product_file/RT9610C/DS9610C-00.pdfMDV3605, MagnaChip, Single P-Channel Trench MOSFET, -30V, -20A, 18.0mOhm, marking V3605, PDFN33-8:http://www.magnachip.com/powersolutions/down.php?filename=MDV3605.pdfHP8K24, Rohm, dual Nch+Nch Middle Power MOSFET, 30V, +/- 27A & +/- 80A, 8.8mOhm & 3mOhm, HSOP-8:https://www.rohm.com/products/mosfets/small-signal/dual/hp8k24-producthttps://d1d2qsbl8m0m72.cloudfront.net/en/products/databook/datasheet/discrete/transistor/mosfet/hp8k24-e.pdfNCEMASLD-64G, FORESEE / Longsys Electronics, NAND flash and eMMC controller, 64GB, 256Gbit x2, 3.3V / 1.8V, 153FBGA:http://www.kindlehk.com/updatefile/file/20190410203634_22235.pdfALC268, Realtek, 2 + 2 ch high definition audio codec, 3.3V & 5V, QFN-48:http://www.hardwaresecrets.com/datasheets/ALC268_Sound.pdfNB679, Monolithic Power, Synchronous Buck Converter, 28V, Low Iq, Fixed 5V, 8A, with 100 mA LDO, marking ALTy, QFN-12:https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/NB679/document_id/4030/NB680, Monolithic Power, Synchronous Buck Converter, 28V, Low Iq, Fixed 3.3V, 8A, with 100 mA LDO, marking ALVy, QFN-12:https://www.mouser.de/datasheet/2/277/NB680_r1.03-371611.pdfCW2013CSAD, CellWise, Low-Cost 1s Fuel Gauge IC with Low-SOC Alert, Lithium‐ion, no sense resistor, 2.5V - 4.5V, marking 2013CSAD, TDFN8:http://www.hytic.net/upload/files/2016/10/%20Cellwise-CW2013CSAD.pdf3165D2W, Intel, Dual Band Wireless-AC 3165, 802.11ac Wi-Fi and Bluetooth adapter:https://www.intel.com/content/www/us/en/products/docs/wireless-products/dual-band-wireless-ac-3165-brief.htmlhttps://fccid.io/PD93165D2RT5077AGQW, Richtek, 7-Regulator PMIC for Intel GLK (Green Lake) Platform:https://www.richtek.com/Products/Power%20Management%20IC/RT5077A?sc_lang=en&specid=RT5077Ahttps://www.richtek.com/~/media/Richtek/Products/ProductSpecs/RT5077A/en/Version2/46309xqxje.GIFhttps://www.richtek.com/~/media/350AF3512EEE48EE9A355CCC1B55ECA5.pdf5~23V & 4.5V ~ 5.5V2x Buck Controller; 1x 5A, 1x 4.5A, 1x 4A, 1x 2.5A LV Buck; 1x 1A VTT LDO; 1x 1A SwitchI2CIntegrated Power Sequence for APL; 1% References; SoiX State for WIN8 Connected StandbyWQFN6x6-52similar RT5074A PMIC for Intel Apollo Lake platform:https://www.richtek.com/assets/product_file/RT5074A/DS5074A-00.pdfAPW8858, Anpec, Power Management IC (PMIC) solution for Intel GLK(*) platform (not used in this design, but has useful Green Lake info):http://www.anpec.com.tw/ashx_prod_file.ashx?prod_id=953&file_path=20181011152242170.pdf&original_name=APW8858.pdfmarkings K4 + AUO (or AUD) + 6T0V10, DFN-8 package, dual N-ch MOSFET, probably 10A

author: Iersuo
author_rank: Newbie
timestamp: December 25, 2019, 10:37:44 am
content: Thanks! A lot of useful info there. Any suggestionon how to take measurements from the PMIC? Without shorting it out 😯

author: Iersuo
author_rank: Newbie
timestamp: December 25, 2019, 01:54:59 pm
content: Also the picture of the PCB's backside in attachment. Not a lot of interesting going on in here, but there is a few test points. If only I would have enough experience to trace these...Also back to the origin of the issue, I can add another detail:The first (pre-fatal) shutdown occured while watching a movie and quickly pulling the laptop towards me. Laptop was laying on the bed. Either coincidence, or static created by the fabric.To clarify, after that, I was indeed able to get the laptop working again for another 5-6 days. Except battery was not charging anymore and laptop only worked off charger during this time.I really suspect that static to the chassis might have killed this laptop and maybe even the first one.Just got a reply from Chuwi that the motherboard of the first laptop has been repaired and now sent back to me. Still skeptical about this though...Any ideas how to track down the loss of power at coils? Afraid to short the PMIC

author: fzabkar
author_rank: Super Contributor
timestamp: December 25, 2019, 08:27:02 pm
content: I think this thread needs input from someone who repairs motherboards for a living. I confess that I don't have much experience in this area.ISTM that your laptop has two different problems, but I can't be certain. Am I correct in assuming that it should normally be able to run from the charger only, with the battery unplugged?AIUI, the RT5077A PMIC powers up with default, internally set, voltages. Subsequently, when the SoC powers up, it can modify these voltages via the PMIC's I2C interface. I could be wrong, but ISTM that the V1P8A and V1P2A rails are sitting at their power-on default levels (1.67V and 1.1V). Subsequently these would be increased to 1.8V and 1.2V, respectively. If I'm right, then it would appear that the SoC's BIOS has not POST-ed. Alternatively, could it be that 1.8V and 1.2V are the power-on defaults and are subsequently reduced after POST-ing?Perhaps it might be worthwhile concentrating on the battery charging circuit, just in case the two faults are related in some way? I would probe the pins of the V3605 MOSFET to see if it is being turned on. Also check each side of the R010 resistor. There is a QFN-20 chip to the left of the ITE chip. Could that be a battery charger IC?Edit:At the risk of introducing a red herring, there appears to be a serial flash memory (SPI) adjacent to the FORESEE storage device. It would probably contain the BIOS code. Its minimum working voltage is 1.65V which is just below the measured V1P8A voltage (1.67V). I don't know what to make of this.GD25LB64C, GigaDevice, serial flash memory, 64Mbit, 1.65V - 2.0V, WSON-8:https://www.gigadevice.com/datasheet/gd25lb64c/Edit #2:You could gain access to the PMIC_EN and SLP_Sn pins via their nearby resistors.

author: Rasz
author_rank: Super Contributor
timestamp: December 27, 2019, 04:06:51 am
content: Quote from: Iersuo on December 20, 2019, 08:55:07 pmgreat laptop indeeddid you buy the second one, or is that a replacement?service people telling you its cpu is not weird, those chinese laptop like products have no protection between cpu and usb, trivial to fry processor while plugging peripherals/just grabbing computer on the side.clicking/cracking sounds while working is often an overloaded switching regulator driving something shorted, whining one is normal for "just" overloaded oneThe only coil with decent capacitor attached (marked by you 19ohm) is 0V, meaning main CPU Vcore is not enabled/failed, might be fried cpu resulting in protection kicking inWhy buy this garbage instead of 3 year old thinkpad?

author: fzabkar
author_rank: Super Contributor
timestamp: December 27, 2019, 05:30:58 am
content: The photos aren't clear, but ISTM that there are ESD protection diode arrays near the HDMI and USB connectors.I'm guessing this is the device:https://www.chuwi.com/product/items/Chuwi-LapBook-SE.html