shybear
Senior Member
Last Activity: 07-06-2026, 10:48 AM
Joined: 01-05-2010
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Have you disabled SECURE BOOT under BIOS ?... -
Bad news. As you said +3.3V_SPI to GND is 0R02 ohms and so inject a low voltage on it, current rise up at 2 - 2,5A . L ooking carefully with thermocamera its clear BGA chip UH1 overheat in a point. Just as last chance I removed CH9 but shorts is still present. Time to looks for an other mainboard.
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Original RTC battery is 2,78V but just to be sure I tested it using a new working battery (3,27V) but mainboard doesn't power on.
Actually I'm testting mainboard keeeping all dismount and also video board dismounted.
Anyway I think the problem could be related on BIOS. On BIOS chip UC5 if power is connected I don't find 3,3V on pin 8 as expected and CH9 give me just 0,02 ohm.
ON PU100 PIN 16 & 17 I've 3,3,V.Leave a comment:
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In these days I tried to looks for something wrong but no luck. Any other suggestion ?Leave a comment:
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PQ 17/22 =>(1-2-3) 19,55V (4) 9,1V (5-6-7-8) 19,8V
PQ 18/23 => (1-2-3) 19,55V (4) 19,5V (5-6-7-8) 19,8V
If (5-6-7-8) voltage is detected on PQ17 / PQ18 on PQ22 / PQ23 is 0,3mV and viceversa. This depend in which usb-c is plugged power.
Searching on schematic @ +SDC_IN that should be 19,5V I get:
PR700 19,55V
PR706 (2) 19,55V
PQ700 => (1-2-3) 19,55V (4) 8,99V (5-6-7-8) 19,55V
PQ20 => (1) 19,55V (2) 9,6V (3) 19,55V
This last values are present always no matter what USB-c is used....Leave a comment:
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Yep you're basically right but not just flip connector, it dependd from the used port of JUSBC1 used so:
using the upper one (PIN 1Bxx) => works PQ2105 so:
+20V_VBUS_1 => 19,78V
+5V_VBUS_1 => 4,88V
(VBUS_2 not working)
using the lower one (PIN Bxx)=> works PQ2101 so:
+20V_VBUS_2 => 19,78V
+5V_VBUS_2 => 4,88V
​(VBUS_1 not working)
Any other voltage test could I try?...Leave a comment:
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OK, I also think that even if battery doesn't charge laptop should powering anyway. I don't have an othery battery to test, anyway I think that first step its that mainboard power on.
So i focused and tested VBUS valuesand I get these results:
+20V_VBUS_1 => 30mV
+5V_VBUS_1 => 0V
+20V_VBUS_2 => 19,78V
+5V_VBUS_2 => 4,88V
So there is something else wrong on VBUS1 section but testing components (except PR2134 that I've replaced) seems to be fine. Any suggestion?
​​​​​​...Leave a comment:
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Could you give me some voltage reference points of cpu rails? I focused on voltage battery because it seem the other voltage are present on the board.
The only thing I've discovered is that PR2134 was shorted that is part of the +5V_Vbus circuitLeave a comment:
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PR62 100K (OK) PBAT_PRES# => 3.3mV and other pin (1) => 3,3V
PBATT1 (pins 1-2-3) => 10,8V with battery connected doesnt' change with or withour power supply and 194mV just with battery...Last edited by shybear; 02-06-2026, 05:46 AM.Leave a comment:
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PIN 20 & PIN 19 10,8V
PIN 18 4,9V
Sorry!...Leave a comment:
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With battery and power (on USB-C) on IC PU700 I've (referred to GND):
PIN 20 => 10,8V
PIN 19 => 4,9V
Just for refernce actually I'm using a standard USB-C power adapter that give 20V - 3,25A (65W)...Leave a comment:
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It's still the original one mounted. 97Wh Type NYRJH 11,4VLeave a comment:
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Sorry my mistake, in post #3 you asked me value between PIN19 - PIN20
"Then, meter in resistance mode and test the resistance between pins SRP & SRN (20 & 19) of the charger IC"
PIN 20 goes to PR727 (10R) and on the other side to PC718 and PC719 and PR715 pin1&2 (0,01R) , so if I test resistance between PIN 20 - PR715 I've around 10R ohm.
PIN 19 goes to PR728 (10R) and on the other side to PC719 and PC720 and PR715 pin3&4 (0,01R), so if I test resistance between PIN 19 - PR715 I've around 10R ohm.
So, as you said:
IC charger PU700 => BQ24780SRUYR...Leave a comment:
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I just tested it agin if I reverse test point I have around 126K. I also tested it with an other meter!Leave a comment:
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I take values with board dismounted, graphic card disconnected and DC oower board disconnected. Power from type-C give 20V 0.043A no matter if battery is plugged or not.
IC charger PU700 => BQ24780SRUYR without battery an power give me around 12Mohm betwwn 18 (PR710 4K) and 19 (PR728 10K)...Leave a comment:
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Dell Precision 7530 Dead
This laptop with Compal LA-F591P Rev.1.0 mb doesn't power on and doesn't charge battery. I've already dismounted all and removed everything, resetting BIOS, check power ON button.
I found boardview and schematic so I started first of all an accurate check of mosfet, transistors and dioodes and others power components. Next I tested voltage and I found on board correctly 19,5V, 5V, 3,3V, 1,1,5V. On positive pin of battery on pins 1,2,3 there shoud be 13,5V but its 0 and so I searched back from it and +20V_VBUS_1 is absent.
Going back to this +20V I checked all mosfet and diodes that... -
Updates aren't working because I suppose that Lenovo removed or changed cloud origin. Anyway if you make the USB dirve with v. 3.5.78 (79?) without launch next U1 for updates it still works. I wish to remeber my suggestions to make USB boot on laptop succesfully.
- use usbfmtpw.exe to format USB suggested FAT32 never mind about the ending erro, then extract 3.5.79.rar on it..
- before to run U1 I suggest to update BIOS on Windows by Lenovo updates app and next shut down.
- before to use USB pen: remove drive, then eneter BIOS settings (F2) and disable Secure Boot under Seurity...Last edited by shybear; 01-21-2026, 02:35 PM.Leave a comment:
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Same problem with same mainboard here. 19V stop on PQB1 even if tested it looks fine as 2nd. mosfet PQB4. On the other side of PCB there is PQ101 (3 pins mosfet) and on gate pin of it I tested 5V. Checking carefully resistance between G-D and G-S its about 500K and on drain and source there are 0V. Bypass PQ 101 conneting gate to ground as suggest at post #8 solved issue.Leave a comment:
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Yep I was looking here too😉Leave a comment:
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ok, thanks, I've seen that its also possible to buy photoled couples (emitter + reciver) so to be sure that both run at same wavelenght.Leave a comment:
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