Aspire 4720z won't run on battery, seeking additional repair options

Hi,

Please help me. Here is the description of my problem [detailed so that you may start from full information]:

Laptop [let's name it as PROBpc] won't run on battery.
PROBpc = ACER Aspire 4720z, running on Ubuntu 12.04, with AS07A41 battery
On boot Setup table, "Phoenix TrustedCore(tm) Setup Utility": System Bios Version V1.3709

Battery of PROBpc is known to be good [tested by installing in another Aspire, where it charged properly and this other Aspire was fully functional with the adapter unplugged from the laptop]. Voltmeter reads 11 volts between the - and + pins of the battery.

PROBpc can detect the presence and type of its battery as shown by this current [now ] information read from the files of ubuntu


filesystem/PROC/ACPI/BAT1,

-... /info:

present: yes
design capacity: 4000 mAh
last full capacity: 1831 mAh
battery technology: rechargeable
design voltage: 11100 mV
design capacity warning: 300 mAh
design capacity low: 73 mAh
cycle count: 0
capacity granularity 1: 32 mAh
capacity granularity 2: 32 mAh
model number: Chapala
serial number: [edited to blank]
battery type: LION
OEM info: SONY

- .../state:
present: yes
capacity state: ok
charging state: charging
present rate: 0 mA
remaining capacity: 526 mAh
present voltage: 12287 mV

The above info is not just a remnant of old data. When another battery [which is bad, charges to only 10% even charged for a long hours] is installed the data are blank on most category except of LION a nd few 0s. When the good battery is installed, data again bacomes similar to above.

PROBpc is fully functional when operating with its AC-DC adapter, with and without the battery.
PROBpc's LED on Power button, Power ON, and charge status [orange when charging, green when fully charged] operates normally.
When the adapter is not plugged, and PROBpc is supposed to work on battery, Pressing the POWER button has no affect,the PROBpc is totally dead: blank and black screen, no lighted LED anywhere, no turning sound of CDROM.

Reading different fora, I have tried without success: removal of battery and adapter and pressing the Power button continuously for 60 seconds, and pressing it repeatedly within another 60 seconds. [supposed to remove static electricity]

From different fora updating flashing the BIOS was recommended. I prepared for this by downloading procedures, precautions, and different versions of phlash.exe, and crisis recovery disk to be installed in a USB with Free DOS.

However, due to the state of PROBpc which is fully functional while on Adapter power, and the risk involved in flashing {not on data lost but on "bricking" the laptop], I suspended flashing option. Also I am able only to get from internet only one version: BIOS3810. I can not find the old version V1.3709. I got a backup copy of the BIOS of PROBpc using backup only option of flashing program. However I have no way of checking if the backup is accurate. Also, even if it is an exact copy of my BIOS, then I will be back to square one if after failure of updating I am to flash back the old BIOS.

Instead of just reading discussion in fora, I now registered in "notebookreview" so that I can get recommendations specific to my PROBpc.

Thank you.

 

Maybe it has a blown fuse on the mainboard, or on the power jack/USB board. There is one one fuse on the mainboard near the battery connector, and another two I think on the power board. They are a 1206 size SMD fuse. You will need to check them with a multimeter for continuity, and if one is blown, then the next question will be: why?, so you will need to look into that before replacing them and installing a battery.

Regards, Rob

 

Thank you Rob. I will look into those fuses.

BTW after waiting for sometime without any replies [but more than a hundred viewings] and after more browsing, I decided [before I received your reply] to take the risk and flash my BIOS with the only available version [for 4720z] from Acer site: BIOS version 13810.

I got an error report as follows:

BIOS update failed: New BIOS is not compatible with the current system BIOS. New BIOS part number doesn't match system BIOS part number.Error code: -120"

As an experiment, what I did next is to flash the BIOS with the one I saved before for this same unit [this should therefor not raise compatibility issues or part number issue].

I got this error report:

"BIOS update failed. Image verification failed. BIOS image check sum verification failed. error code:-104.

The good thing is that this laptop is still working fully except for the non-power up when using only the battery.

I will "exercise", based on the service manual, how to disassemble the laptop deep down to the boards. I will reply after I have tested the fuses.

Thanks again.

 

Rob,

One fuse labelled 7 [7 Amperes based on Little fuse company table] right behind the power jack tested good. I have not yet disassembled the laptop,-making my measurement through a hole I cut in the battery compartment just behind the power jack.

Taking off the plastic lid at the bottom of the laptop; I can see portions of the motherboard. On the board containing the battery connector, are two SMD components [I labelled them as "fuses"] smaller than 1206 and two coils labelled PL8 PL7 [see attached picture CoilandFuse.jpg]. See also attached chargercct.jpg. The two fuses are connected in parallel to each other [continuity test shows that they are open circuit, "blown"]. My analysis is that they are the equivalent of the PF1 in the chargercct. Also PL8 and PL7 are equivalent to PL5 and PL4. Continuity test showed that PL8 and PL7 are connected in parallel, and that one terminal of the 2 fuses in CoilandFuse is connected to the positive terminal of the battery connector. The other terminal of the fuses is connected to the terminal of PL8-PL7. The connection matches that in chargercct.

I then made measurement without the battery:
There is no voltage at the terminal of PL8-PL7 with respect to ground when the adapter is plugged to the laptop, with the laptop off and charging LED lit. When the power button is pressed, PL8-PL7
started to be below 1 volt from ground. This went up to 1 then 1.25 V as the brightness of the screen increases. PL8-PL7 gets hot after a few minutes [but bearable to brief touch]. The same voltages appearswhen the battery is installed.
I would like to see the circuit of the "Power Board" power [jack/ USB ] since it seems that the blowing of the fuse is related to the circuit between Vin and BAT points.

I have only pictures of the Power Board from suppliers sites in the internet. I have been searching for the schematic of the power board but could not find any.

Citing of links to schematic diagram of the Power Board will be much appreciated from you or other readers of this thread.

 

Sorry,here are the mentioned attachments. .

I had to go to FAQ to learn how to reply and attach files.

 

The 4720 is very easy and quick to dismantle completely, and doing this will give you total access to the mainboard and power jack pcb. With a meter and your eyes, it is easy to track the high current paths through the mainboard and power jack board. I haven't found a schematic of this board, only the mainboard, but if you suspect there is something wrong with the power board(which I do), it is very cheap to replace and save yourself a lot of time. You can pick one up on ebay for about $20, sometimes even less.

As for the bios, I don't believe it has anything to do with your problem and you might cause yourself a bigger problem with a bad flash. Only update it once the computer is running properly, and then only if you know how to recover from a bad flash. Secondly, if the computer is running fine with all its installed hardware, there is usually no reason to update a bios anyway.

Oner last thing...make sure the battery is removed and the external power is unplugged before dismantling the computer. There are some live power connections going through the ribbon cable to the power on/off board.

Regards, Rob

 

I have replaced the keyboard of this laptop before. I found the dis-assembly easy, but returning the ribbon cables back to their connectors/sockets difficult.

I will schedule the dis-assembly and post later.

 

Re-inserting the ribbon cable should be very easy. Perhaps you may not realize that the black strip adjacent to where the cable enters the connector actually hinges up to release the cable. To re-insert it, you slide the cable into the connector making sure of exact alignment, then hinge the black retainer bar back down. If you pull the cables out and push them back in without releasing the black tension bar, the cables will be damaged. You have to swing the black bar up very, very carefully, as they can break quite easily, which can be a slight disaster.

Regards, Rob