[Solved] Repair / LA-6847P Rev : 1.0 / Shorted - Page 1
Forum section: electronics / repair

author: xan
author_rank: Regular Contributor
timestamp: August 09, 2018, 10:10:28 am
content: Hi Everyone!Back again this time with LA-6847P board, it's from a toshiba nb and won't power on it comes with a power adapter 19v / 4,74A and notebook is working with nominal 19v / 3,95A. I just recover it with a new Si4483ADY (PQ8) like the shorted one before... and a new polifuse on B+ line (PF2) but after 1 sec after connected to the adapter, a small whistle come from it and back again with Si4483ADY shorted like beforecould you help find witch section is shorted and give it a new life. Below schematics and datasheet, i will provide some measurements after but it's so hurting if i remove shorted mosfet 19v is stable but i can't measure so much more on the board instead if the component it's on the board adapter goes on under protection mode and stop regulating power, same with battery pack..Thank's

author: xan
author_rank: Regular Contributor
timestamp: August 09, 2018, 01:16:33 pm
content: below 1st results.

author: Rasz
author_rank: Super Contributor
timestamp: August 09, 2018, 04:16:03 pm
content: if PQ8 fries there is something bad behind it

author: xan
author_rank: Regular Contributor
timestamp: August 09, 2018, 04:32:28 pm
content: 1st) Do You think PQ7 it's safe ? (i just burned it 2 times 350° cause it's nearest..) did you see continuity values are ok ?2nd) It could be PF2 (p.43) BATT_S1 or i misunderstood diagram flow ? i think gate voltage about 7.5v on PQ7 it's ok so PACIN flow from PR64 correctly...3rd) Should i remove PR45 to isolate the two Mosfet and goes on ?

author: Rasz
author_rank: Super Contributor
timestamp: August 09, 2018, 06:10:04 pm
content: 1 "The definition of insanity is doing the same thing over and over and expecting different results"2 fixing laptops is not about randomly guessing which component to replace3 use lab supply with current limit. Dont fix laptops using factory PSU, use a bulb at the very least.4 remove fried PQ8, measure resistance to ground on B+ and BATT+ points on diagram5 does it work on battery alone? dont test if you didnt already, it might result in another fried component

author: xan
author_rank: Regular Contributor
timestamp: August 10, 2018, 01:21:26 pm
content: Quote from: Rasz on August 09, 2018, 06:10:04 pm(first time another from other lab, second it was me)Quote from: Rasz on August 09, 2018, 06:10:04 pmof courseQuote from: Rasz on August 09, 2018, 06:10:04 pm(i'm looking for a good 'cheap' one)Quote from: Rasz on August 09, 2018, 06:10:04 pmDesoldered PQ8 resistence to ground 'diode mode' = 0 B+ / BATT+ line taken from 'PC4210U_1206_25V6M +' to ground 'diode mode' = 0.570 See attachments i have some extra measurements. (i have teste much more things i got 5v on a small resistor 4.7u ..etc, i will write after...)Quote from: Rasz on August 09, 2018, 06:10:04 pm(for now PF2 tested on continuity not permit to make more test i need to desolder it again.. should it stay on board ? For now i placed battery pack twice and i get about 10.5v on a side of PF2 .. but nothing else on that line...)

author: Rasz
author_rank: Super Contributor
timestamp: August 10, 2018, 10:06:27 pm
content: Quote from: xan on August 10, 2018, 01:21:26 pmso now you know where the problem isB+ powers everything, now go down the diagram, locate PL11 PL20 PL21 PL801 etc and start pull;ing them one by one and checking which side the short is

author: xan
author_rank: Regular Contributor
timestamp: August 12, 2018, 12:08:44 am
content: thank's hope for the right way! ok all this filter pl10 coil it's ok and pl11/pl19(seems a small coil)/pl20/pl21/pl601/pl801/pl802 all to ground = 0 ... still inpsecting... hope i pulled everything on B+ rail ... the lastest test are for pr45/pq6/pl19/pc73/pc74/pc75/pc23/pc24/pc25/pc26... some of it main rail.I found pc27 (above pq7 on schematics) and pc28 (above pq8 fried one) both fail continuity to ground = 0 ... (is this making any sense?)anyway for now seems first component to fail continuity = 0 are pc27 and pc28i will make more measurements tomorrow..... any idea ?

author: Rasz
author_rank: Super Contributor
timestamp: August 12, 2018, 02:53:45 am
content: Quote from: xan on August 12, 2018, 12:08:44 amobviously, you are supposed to pull one side of those coils into the air and check which side is shortedQuote from: xan on August 12, 2018, 12:08:44 ampc27 cant be shorted, unless you managed to fry something in the meantime, it was fine before your second post in the threadpc28 is 0 to ground because it is sitting on B+

author: xan
author_rank: Regular Contributor
timestamp: August 12, 2018, 04:33:55 pm
content: of course i'm wrong ... my fault pc27 is not shorted!! anyway... i'm swimming around right no... no destination...go now stillsome more i have power ic voltage above

author: xan
author_rank: Regular Contributor
timestamp: August 13, 2018, 05:11:11 pm
content: Do you think all the component on B+ line could be shorted ? i mean all mosfet and some caps ? i have strange readings across all the line...PQ17 +gd i have at start 550 and after goes to about 1900 and +gs start from 0 and goes to 1300... +drain to source = 550 and reverse 505 this meaning it' fried ? or it's the effect of b+ shorted...again on PQ6 sitting on B+ it's ok the gate is isolated = gs = gd = (and reverse) = 1 but ds = 550 and sd = 505...again PQ19 gd = 1 it's ok +gs = 1600 -gs = 450 ... are this test useful to see if a component it's on fail and should be removed? do you experience too ?(sides of the mb down)

author: Rasz
author_rank: Super Contributor
timestamp: August 13, 2018, 09:49:33 pm
content: >from 0 and goes to 1300charging capacitor

author: xan
author_rank: Regular Contributor
timestamp: August 15, 2018, 03:22:01 pm
content: that's right it was caps, i post updated value on schematics attached... i've taken more accurate voltage measurements i need to know from where 0.30 v coming from... maybe it's near the solution..B+ is out of this 0.32v it's around csin csip power IC and batt+ what do you think ? are the value for the power controller on tollerance ? the circle it's coming to the closure! (excluding all the possible damages along the B+)

author: xan
author_rank: Regular Contributor
timestamp: August 17, 2018, 06:00:52 pm
content: Here some update, i finally repair with success 1st B+ line, it's not anymore shorted but i dicovered some other shorts along B+ like expected... but i start test again.. and again... (+VGA_COREP / VGA_CORE / +VTTP )what do you think? could be vga 216-0774009-A11PARK_FCBGA631 - UV1D - PARKR1@ ?? do you experience ? Some suggestion to be quickly?

author: xan
author_rank: Regular Contributor
timestamp: August 17, 2018, 06:05:53 pm
content: and here second part

author: Rasz
author_rank: Super Contributor
timestamp: August 18, 2018, 01:54:50 am
content: some legend for the colors would be niceI would venture a guess its fine now, that cap was the sole fault, minus all the things you managed to screw up in the process of "repairing it"

author: xan
author_rank: Regular Contributor
timestamp: August 18, 2018, 07:49:22 pm
content: update i cut out all +VTT / +VTTP (p.42 via jumpers pj11 pj13) and next line +1.05v (p.46 via jumper pj20) now only next to +1.05v is on short nothing to repair there.. VTTP / VTT is safe but i have low resistence and then chargin cap.... still measure...What's that 1.05 used for ??Here backside PCH coreis that? R? C? 50% of chance! anyway is on short!Could do you help to locate missing component on schematics ?

author: Rasz
author_rank: Super Contributor
timestamp: August 19, 2018, 11:10:42 am
content: I really dont understand what you are doing at this point. Yes, low voltage high power rails for GPU and CPU naturally have low resistance, no those are not shorted.

author: xan
author_rank: Regular Contributor
timestamp: August 19, 2018, 12:19:55 pm
content: Ahhh yeah sorry ... i am little bit confused...??? so.. i will power on the machineB+ is safe... but i don't expect machine pass over VALW steps.. Let's do it!

author: xan
author_rank: Regular Contributor
timestamp: August 19, 2018, 03:54:24 pm
content: led light on -> now fan spin on -> 5 seconds.... but like i say no video the system stop itselfany suggestion for inspect GPU_COREP/GPU_CORE, +1.8v, and +1,05vskeep you updated next!

author: xan
author_rank: Regular Contributor
timestamp: August 23, 2018, 09:11:22 pm
content: Here a little update on voltage (after B+ no more shorted), do you think somethings is wrong on this voltages... ?(see attachment, don't take care about continuity info)Thank's

author: Rasz
author_rank: Super Contributor
timestamp: August 23, 2018, 09:28:33 pm
content: 5V shouldnt be 6V, maybe something wrong with TPS51125 feedback

author: xan
author_rank: Regular Contributor
timestamp: August 23, 2018, 09:35:05 pm
content: ooh sorry.. my fault on png conversion.. it's 5.14v...(attachment better res values)

author: Rasz
author_rank: Super Contributor
timestamp: August 23, 2018, 09:37:55 pm
content: so the problem is not on powerlines

author: xan
author_rank: Regular Contributor
timestamp: August 23, 2018, 09:41:47 pm
content: should i probe testing again voltage during power on pressed, on all of the other jumpers ? PJ101 PJ23 etc etc ... right ?

author: Rasz
author_rank: Super Contributor
timestamp: August 24, 2018, 09:50:28 am
content: why? according to what you already measured problem is not on power rails

author: xan
author_rank: Regular Contributor
timestamp: August 24, 2018, 03:43:24 pm
content: of course... infact i have this readings... i have only to confirm pj20 value, i discover it was desoldered (and i forgot it to solder back)... i keep close it and test again..

author: xan
author_rank: Regular Contributor
timestamp: August 24, 2018, 04:36:05 pm
content: After solder to close pj20 power is stable, all the 2 led (1st power/suspend 2nd batt charge/full led thought battery is disconnected, i never try pull it back for now) are on green state and remain on green light for all 10 minutes during the machine power on, fan near gpu start spin and stop after but in few seconds temp grow and start spinning faster at full rmp, seems all it's ok! but still no video, no boot...

author: Rasz
author_rank: Super Contributor
timestamp: August 25, 2018, 01:10:51 pm
content: put a scope/ logic analyser on bios lines and see if its being loadedor buy a post code card for laptops

author: xan
author_rank: Regular Contributor
timestamp: August 27, 2018, 06:08:47 pm
content: no scope... i just try to reload bios with usb key and wincrisis utility to have a fresh bios firmware... but unlucky for now... pressing Fn+B, power cord plugged and power on, fan start spinning faster for few seconds, then stop itself.... but no luckeverythings is the same but now Fn+B just make half second fan spinning and then stop... and i think the flashing procedure not really start..Another impression, keyboard seems to work, but no lights for caps-lock and num-lock... try the common Ctrl-Alt-Del... obviously nothing happens, machine stay turned on.

author: xan
author_rank: Regular Contributor
timestamp: August 28, 2018, 05:56:14 pm
content: 1) What kind of test equipment do you suggest ?(seems a pcie tester is the faster and cheaper solution, but i don't see around some half mini-pcie equipmet so a standard mini pcie should work without screw it on the board right)2) With some kind of post debugger should i solder on motherboard debug pinout ? or simply put into mini pcie the debugger ?

author: Rasz
author_rank: Super Contributor
timestamp: August 29, 2018, 12:26:09 am
content: afaik for laptops you plug into LPC (https://en.wikipedia.org/wiki/Low_Pin_Count) or dedicated debug port

author: xan
author_rank: Regular Contributor
timestamp: August 29, 2018, 09:02:24 pm
content: It's Done!! thank's for the tips i can't believe... i discovered i had bad soldering on pj8 and pj10 on vga_corethe code given from Debg post card suggest me to check that area again!Anyway TYFAYS!c660 back to life!(As you said before B+ after two fried Mosfet and a fuse short was only caps on B+)