Laptop completely unresponsive - Sony Vaio VPCSB190X

blinky1041

Honorable
Oct 5, 2013
3
0
10,510
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Hello all, and thanks for taking a look at this issue.

My roommates laptop suddenly stopped working the other night. The story is that it had been sitting, powered up, with the charging plug inserted into the jack. He moved the laptop and realized that the charging plug was not fully inserted and pushed it in fully. At that point, the computer turned off (without shutting down) immediately, without prompting. Says the battery charge was indicated at ~1/3 full when this occurred. He reports witnessing no physical or static electrical shocks at the time.

Now there is no response whatsoever from the computer. Will not boot or power up at all. No charging or hdd activity lights, nothing. This status does not change regardless of whether or not plugged into charger, with or without battery. 30 second power button push has had no results.

I did some very basic troubleshooting with the following results:

  • Power button switch operating correctly, assuming dpst nc switch, both poles in parallel
    Ribbon cable from switch pcb to pcb on keyboard has continuity on all contacts (didn't check for shorts)
    19.4 VDC @ daughter "power" pcb (where plug and battery power inputs are located) input when plugged into charger
    Battery voltage is suspect in my limited judgement. I measured the following voltages from battery ground (black heavy wire) starting at the adjacent contact:
    2.266V
    0.2mV
    0.0mV
    0.1mV
    3.222V
    4.0mV (red heavier wire)
I'm not sure of the internal structure of the battery (assuming 3S nP for 11.1 V rated Li Ion). My basic understanding is that the positive and negative battery terminals should be at the voltage that the pack is rated for (11.1V) and not 4.0mV. and that the other contacts are used for balancing, although I don't know why there are 5 balancing terminals.

If the above assumptions are correct, it would seem that the battery is toast.

The battery cannot be the only problem as the computer is dead with the battery removed as well.

Any ideas?

Thanks again.
 

blinky1041

Honorable
Oct 5, 2013
3
0
10,510
0
Found out what the problem was: I was concentrating on the battery charging board. Turns out that there was a short between the power input and ground terminals on the mother board.

Lacking a regulated DC power supply, I connected a fresh AA battery in series with a multimeter set on DC current measuring and applied power to the power input and ground on the motherboard. As the AA supplied nearly 10A to the shorted connection, I only applied power for approximately 3 seconds at a time and felt my way around the board.

One of the 3 surface mount 10uF 25V smoothing capacitors on the input circuit feeding the power supply on the motherboard heated up very quickly. I removed it from the board and voila: the battery charges and the computer now boots. I'll hold off putting it into service until I receive a replacement, but the problem seems to be solved!
 
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