UMPC Sony Vaio P (no power/video, power led not always on, 1.8v rail missing) - Page 1
Forum section: electronics / beginners

author: Haruki
author_rank: Contributor
timestamp: September 04, 2025, 08:45:17 pm
content: Hello, i bought this 2009 UMPC Sony Vaio P for just 20€, sold as faulty / to repair.Seller said "no power", but the orange charging light is present, so is not "full dead".There are few tiny boards inside, cleaned all, no visual damage on the components but for sure it was already opened before.That's part of the main board where the big coils are and what i found:11vmain rail ok (psu is 10.5v)3.3vL1701 and5vL1700 on standby okL2100 should be for the battery charging (disconnected), 0.086v hereWhen i try to power it on, i have 2 different situations.1) Usually, green light is not present and that's the new voltages:2.5vL1062 ok1.095vL1601 ok0.850v L1500 +VCPUCORE up to 0.004v then0v1.8v L1600 (DDR2 ram) up to 0.140v then0v2) Sometimes (and not sure why), green light is present and that's what change:0.850v L1500 +VCPUCORE is now ok and stable1.8v L1600 (DDR2 ram) start with 1.8v but after 2-3 seconds drop to 0v(0.850v +VCPUCORE is still present as all the other voltages above!)So...seems that something is off with the 1.8v ram rail.L1600 1.8v inductor has 4k ohms resistance toGROUND, so is NOT shorted. This is the first thing that I checked.It's as if sometimes the PC finds something wrong and won't start up (no green led, case 1 more often), blocking only certain voltages (cpu core 0.850v and 1.8v rail), while other times (green light, case 2, rarely) everything starts up but after a few seconds it “notices the anomaly” and the 1.8 voltage rail is cut off... but the computer does not shut down and the other voltages remain active.The 8 ram chips are soldered on the board so i can't remove them or test with another ram.I can't find any repair video about it, but i found thefull schematic of the mainboard MBX-187, it's below! 1.8v rail is at page 18!It's a valuable little "retro" pc so before i start to mess with it, any help is really appreciated. Thanks!

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: September 05, 2025, 10:36:50 am
content: Check the inductor, diodes and MOSFETs.

author: Haruki
author_rank: Contributor
timestamp: September 06, 2025, 07:57:34 am
content: That is...super generic. For the inductors i already wrote what voltages they have. Could you be more specific about what part I should focus on and what I should do? Thanks...IC1600 MAX17017 seems the chip where the +1.8VSUS start (with other voltages).I tested SUS_ON (pin 39, ONA) and PWRGD_+1.8VSUS (pin 26, POKA) of the chip during startup and that is the results in case 1 or 2 (when also the green led is on, not always as wrote before).

author: Simmed
author_rank: Frequent Contributor
timestamp: September 06, 2025, 10:55:34 am
content: Quote from: Haruki on September 04, 2025, 08:45:17 pm4k ohm coilmost power stage inductors are <0.1ohmdesolder and check ?** yea i just saw the schema , 8A is not 4kRso when inductor is not therecheck downstream for short / irregularity ?Q1600 i wonder what it does ? 100R ?SL1608 is a wire jumper ?

author: Haruki
author_rank: Contributor
timestamp: September 06, 2025, 12:04:55 pm
content: Quote from: Simmed on September 06, 2025, 10:55:34 amEhm....the 4k ohms on the first post is the resistance of the L1600 1.8v inductorwith ground....not between the inductor itself... i know that the coil is like a wire and should be 0 ohm and it's fine...I thought it was obvious that the written measurement was to make it clear that the inductor is NOT shorted to ground, and that was the first thing I checked.Also because, as I wrote above, in case 2) the 1.8v is present for few seconds, then drop to 0v, while all the other voltages around the board is still there.It's as if sometimes the PC finds something wrong and won't start up (no green led, case 1 more often), blocking only certain voltages (cpu core 0.850v and 1.8v rail), while other times (green light, case 2, rarely) everything starts up but after a few seconds it “notices the anomaly” and the 1.8 voltage rail is cut off... but the computer does not shut down and the other voltages remain active.I will edit the first post to make it more clear...

author: Simmed
author_rank: Frequent Contributor
timestamp: September 06, 2025, 12:41:49 pm
content: hmmm oklooking at max17017 pdf diagramyou probably need to check PWRGDALWthe schema has the red box ONA POKASUS_ON and RUN_ON are 2 different logic sent to this max17017 = are these ok ?yea sounds like SUS_ON is turned off, but why ? sorry i cant see what is outside the diagramthe above are just myguesses

author: Haruki
author_rank: Contributor
timestamp: September 06, 2025, 12:45:57 pm
content: I edited the first post, maybe now is more clear, reload the page.As for the tests on that chip, I only checked SUS_ON (pin 39, ONA) and PWRGD_+1.8VSUS (pin 26, POKA) and I did the 2 red box on the image to make clear what i tested.Full schematic pdf of the mainboard is on the first post! max17017 chip, +1.8VSUS etc are at page 18.I will try to check the other one you wrote. Thanks!EDIT: PWRGDALW pin 13 SHDN is 3.3v always, on standby and also on case 1 or case 2.+1.5VRUN (pin 7 and 8, OUTD) i think have a problem also...on case 1 voltage is up to 0.7v then 0v, while on case 2 is up to 1.5v few seconds then 0.7v.

author: Simmed
author_rank: Frequent Contributor
timestamp: September 06, 2025, 09:45:35 pm
content: from OUTA to OUTDi think max17017 is done with some sequential delayOUTD is last to turn on, look at ONA to ONDPOKC signals ONDso ONA + ONB always turns on firstmax17017 pdf says it has some fault turn off featureso you need to check the FBA ok? CSPA/NA ? R1602 ? R16xx for FBA ?i didnt fully read if max17017 has current sense for FBB FBC ?if OUTC over current ? im not sureOUTC > VCCP > CPUso is VCCP short to GND ?just my guesspage 20 have some array of MOSthe supplies go fromxxALW > xxSUSxxALW > xxRUNxx ALW > xxRSMi suppose all of them stayed on ?

author: Haruki
author_rank: Contributor
timestamp: September 06, 2025, 11:08:50 pm
content: Uhm ok, will try to check them also... I tested the board again with the bench psu this time (10.5v) to see how much current are there.standby/off 0 ampere | case 1 (no led) = 0.170a then 0 | case 2 (led on) = 0.220a two seconds then 0.092aNot sure if this can help!

author: Haruki
author_rank: Contributor
timestamp: September 17, 2025, 08:08:09 am
content: Hello, just writing here to give a conclusion. I fixed the tiny laptop!In a last attempt before give up, i tried to push some components around the board just to be sure that nothing was half desoldered or damaged (but visually fine), and that's happened (photo n1).A little resistor near a secondary MAX chip (not the one where we are focused) moved and was bad with wrong value (220k on the schematic).Replaced it with another one (more big but same value), and now it's working fine.1.5v and 1.8v are there and the umpc turns on!From the schematic that resistor seems super important and probably why i had case 1 / case 2 and unstable voltages before.Sadly the Vaio is a bit worn out, with two missing keys, wrong screws and the seller broken many plastic clips so it doesn't close well...but for just 20€, it's fine(they are sold for much more!)I will try to restore the original OS with all the oem stuffs (Vista best OS ever).So many days and at the end was just a hidden bad resistor. Thanks @Simmed for the help anyway!