Hp 15 la-a993p ec_on not present

[mcplslg123]

I have this mb LA-A993 REV 2.0 and its not turning on. Dc jack light present. EC_RST# & EC_ACIN present but no EC_ON signal on KBC9012. EC_ON is the enable signal for RT8243A(PU301,pin 13) and hence i dont have +3VALW and +5VALW though +3V LDO and +5V LDO present on pin 15 and 14 respectively.

I have replaced KB9012 and programmed it with a known good dump, flashed main bios with HP virgin bios with correct BID. Still no EC_ON. Replaced PU301 also-same no result.

Impedance on all coils/jumpers checked and there is no short.

How to proceed further? Why EC_ON signal is not generated by kbc??

LA-A992P schematic i'm attaching and is same as LA-A993p. Btw, having same issue on another HP LA-A994P.

[piernov]

Re: Hp 15 la-a993p ec_on not present

Weird one… Are you sure you are using the correct AC adapter power rating?
No reaction when triggering power button? Try with a charged battery as well if possible.

Double check EC solder joints under microscope and try with another EC dump maybe.

Also make sure all the power rails for the EC effectively get to its pins.

[mcplslg123]

Re: Hp 15 la-a993p ec_on not present

Thanks @Piernov for replying.Here are the replies
01 Adapter is HP original and tested ok.
02. Yes, no reaction when trigerred. Checked no voltage rising even for a split second on 3V and 5V Coils as well as on EC_ON pin.
03. Ec solder joints are perfect under microscope.
04. Yes the power rials for EC to work are all present .
05. Not tested with a charged battery. Will check and revert back.

If i inject 3V from another dc supply on enable pin of pu301, then i do get 3 & 5v on coils but still it doesnt switches at all.

[SMDFlea]

Re: Hp 15 la-a993p ec_on not present

Have you looked at +3VL, RP8,DK1 etc

[Techtiger]

Re: Hp 15 la-a993p ec_on not present

Have you looked at +3VL, RP8,DK1 etc

Maybe the PR8 is faulty or PR315

[pyry]

Re: Hp 15 la-a993p ec_on not present

EC-ON is a signal that comes out of the kbc after you press the power button. That's why there is no +3VALW and +5VALW
make sure that the power button status change, reaches the kbc
sorry for my English

[mcplslg123]

Re: Hp 15 la-a993p ec_on not present

Thanks for replies to all. PR8 is not faulty and PR315 is ok as per schematic. I know EC_ON is active only after power button pressing. I have already mentioned in my description that its the enable signal for 3/5V regulator ic and hence i dont have 3/5V ALW signals. Power button drops to zero and rises on pressing-so its fine. +3VL is present and i have looked on DK1 and found nothing wrong.

Btw, i wouldnt have posted here if it was very simple thing or if the schematic can explain the fault. I have probed thoroughly but couldnt find anything wrong in my analysis. Hopefully, someone here has encountered it and knows how to rectify it.

PS: I have another LA-A994P mb with exactly the same fault and this mb was tested ok but was lying unused for almost a year and now when i tried to turn it on , it too have developed the same fault-NO EC_ON. So , most probably, it should be a minor fault and there may a trick too rectify it. I came across ayoutube video with same problem but it didnt disclosed the solution as its a paid video by some indian techie.

[mcplslg123]

Re: Hp 15 la-a993p ec_on not present

@piernov, tested with a charged battery-same fault

[anshad]

Re: Hp 15 la-a993p ec_on not present

Interesting fault. You are more experienced than me and seems to have already tested and verified all the regular failure points. Please Let us know the solution once you find out so may helpful in future for others.

Btw, if you have DSO, check all those voltages and signals using DSO and make sure that no glitches/anomalies present on those.

[mcplslg123]

Re: Hp 15 la-a993p ec_on not present

@anshad, i"ll surely share if i'm able to solve this puzzle. So far not succesful. ADP_ID is also good.

[caspian]

Re: Hp 15 la-a993p ec_on not present

It seems that this laptop is one of those that take a lot of work.
Does the laptop charge the battery ?
Now, you can check some input pins of KB9012 to find a wrong one. for example, pin 65, 115, 77, 78. or you can measure resistance on KB9012 pins to find a shorted one.
If they are all fine, since you have replaced KB9012 only once so far, it is possible that this new KB9012 is defective too. I guess you got it from a donor board.

However, it is possible that all these steps lead to no change too.

[mcplslg123]

Re: Hp 15 la-a993p ec_on not present

It seems that this laptop is one of those that take a lot of work.
Does the laptop charge the battery ?
Now, you can check some input pins of KB9012 to find a wrong one. for example, pin 65, 115, 77, 78. or you can measure resistance on KB9012 pins to find a shorted one.
If they are all fine, since you have replaced KB9012 only once so far, it is possible that this new KB9012 is defective too. I guess you got it from a donor board.

However, it is possible that all these steps lead to no change too.

@caspian, thnx for your reply. I've already checked ADP_ID, LID_SW,EC_SMB clock & data lines, EC_RST, PCH RSMRST, RTC sections thoroughly. Just to summarise, every basic requirement for 9012 to be working has been checked and nothing is wrong.

9012 I've replaced thrice-2 from donor boards and 1 new. Thay have been flashed with a known good dump as well. All the kbc's are i beleive working as i tested one of those kbc on dell inspiron 3521 and it worked perfectly. So kbc is fine but still no EC_ON.

[SMDFlea]

Re: Hp 15 la-a993p ec_on not present

The EC_ON works on a seperate power plane in the KB9012. Pin 112 is GPXIOD02,its ALW_PWR_EN in the datasheet,and EC_ON in the schematic.Page 232 (KB9012) has the power latch logic.Now, i`m a bit lost on the next bit on page 234 with the comparison behaviour,the best i can make out of all that VCDAC, VCCR,PA0_REG stuff is it needs VCIN0,VCIN1 to work on Pin 102 and 109.Those are VCIN0_PH , VCIN1_PH in the schematic.There are 2 references to them on page 44 .Check PR 25,26,27 .

[Weelcup]

Re: Hp 15 la-a993p ec_on not present

Hi
I dont know if my contribution will add anything more than what all the friends suggested.
But if it was me, I would do the following.
-Check for any shorts on power rails (specially 3v 5v you already did)
-Check for the 3.2v on the power button and try to short it to ground to turn on instead of pressing the power button.

Then of course program both chips (bios and EC)

I would also suggest you to check all EC pins if case there was any short to ground.

I remember that I had an acer board that refuses to provide EC_ON signals and the reason was a 3pin diod marked X321 which was related to the power on circuit. I noticed the same 3pin diode on couple of other boards in relation to the power on sequence. On lenovo g50-70 for example that diode is located on the power button circuit board. In any case you found one then it should out the 3.2v before even pressing the power button.

Regards

[mcplslg123]

Re: Hp 15 la-a993p ec_on not present

@weelcup, your all suggestions have been already taken care of. No short in 3/5V rail, No pin of kbc other then ground is shorted, bios is known good. The 3 pin diode you are talking about is perhaps LID Switch and its good.

I'll look into the points highlighted by @smdflea.

[mcplslg123]

Re: Hp 15 la-a993p ec_on not present

Here is a quic update. I left the two boards with cmos battery unplugged for last 15 days almost and today i checked both mb's. To my surprise, both mb's were showing 3/5V ALW on coil, EC_on was present. Both mb turned on and i got display. Now, i"m scratching my head.

[caspian]

Re: Hp 15 la-a993p ec_on not present

I think you should keep track of resistance on EC_ON for a while without/with the CMOS battery.

[mcplslg123]

Re: Hp 15 la-a993p ec_on not present

I think you should keep track of resistance on EC_ON for a while without/with the CMOS battery.

Yeah, its a good idea. Will take a note

[bladimir guaza]

Re: Hp 15 la-a993p ec_on not present

loading port there is this the damage

[raajkumar]

Re: Hp 15 la-a993p ec_on not present

I have a same issue on LA-B972 Board. Unfortunately i don't have schematic for the mboard. I checked with similar schematics but i don't have RSMRST, EC_ON on this mboard. does anyone having any clue.