Toshiba L500 blinking power LED

[spleenharvester]

Was sold to me as "powers up, but no display".

On receipt it doesn't even do that. There is no i3 CPU or DDR3 RAM plugged in - but upon plugging in the adapter, the power light flashes extremely rapidly. A relay can be heard clicking somewhere.

Noticed on visual inspection a small MOSFET is missing most of its numbering - maybe a burn mark - the pads (shown below) in this area read only 30.8ohms to ground. Is this normal, even without the CPU plugged in? This is the MOSFET: http://pdf1.alldatasheet.com/datashe...PCA8028-H.html

Caps in middle of CPU socket have stable 1.4v though.



Felt around the board and nothing seems to get hot. There is 19v at VIN but I can only find oscillating 1v~2v voltages in the other areas of the board, as well as lots of 12~13v voltages.

Unfortunately no schematics for this one. LA-5321P, not even those dodgy sites seem to know of its existance. :-/

Cheers

[spleenharvester]

Re: Toshiba L500 blinking power LED

MOSFET shows only 037 on the DMM on the Diode test. Think I may change. Would this cause the issue I am experiencing?

[spidey]

Re: Toshiba L500 blinking power LED

try this one:

http://tr.scribd.com/doc/86898760/La-5322p-Nswaa-Ntwaa

[spleenharvester]

Re: Toshiba L500 blinking power LED

Most of the pages aren't visible in that preview Scribd does my nut in. If anyone has an account there I'd much appreciate it

Though I can see from that, the ISL62883 +VCORE line is okay, which means the B+ line must be okay. The MOSFET is attached to one of the APW7138 lines.

[spleenharvester]

Re: Toshiba L500 blinking power LED

New development: with AC + battery plugged in, LEDs are stable, battery charges - it powers up then dies a few seconds later.

With battery on its own, there are no signs of life.

[spleenharvester]

Re: Toshiba L500 blinking power LED

Okay, two questions:

1) Can I replace the TPC8028 () with a TPC8036 () or a TPCA8023 ()?

I'm guessing the TPC8036-H will be the best bet, because in a board I have it has 4xTPC8028 on the schematic but 2xTPC8036-H on the actual board so they must be cross compatible.

2) Should I replace it with a hot air gun? Given it's a QFN8 chip with pads underneath I can't use a soldering iron can I?

Cheers

[spleenharvester]

Re: Toshiba L500 blinking power LED

Bump

[degutji]

Re: Toshiba L500 blinking power LED

Try this one bro

[spleenharvester]

Re: Toshiba L500 blinking power LED

That one's for the Inventec socket P version but thanks anyway man

Also new situation, there are two MX25 IC's on the board, I am not sure which is the BIOS chip. The larger one (MX25L3205) is recieving 0v, whereas the smaller one (MXIC 25L2005C) is receiving the 3.2v. Surely if the BIOS was recieving no power it would not power up at all?

I'm starting to think this shorted MOSFET is supplying the power to the BIOS chip, everything else seems to have power except when only on AC.

[sparker1]

Re: Toshiba L500 blinking power LED

Try this one then,

[spleenharvester]

Re: Toshiba L500 blinking power LED

Seems to have some similarities mate thankyou

Also, replaced PQ31 TPC8028 today, no change - the replacement MOSFET also reads as short but is fine out of circuit.

Removed PL7 (see OP pic), the short is on the side furthest from the MOSFETs. So apparently unrelated. I can't see where it connects to - the pad has 29.7 ohms resistance to ground but I can't find anything else with that.

[spleenharvester]

Re: Toshiba L500 blinking power LED



All components in red read as 29.7 or 27.4 ohms, often closest side to the HM55 chip. I've tried a light reflow on the chip with no change.

Should I keep removing stuff? Are the SMD 'lytics likely to be shorted? Are tiny inductors likely to be shorted?

[degutji]

Re: Toshiba L500 blinking power LED

Looks like short on CPU area, try update bios first for make sure

[spleenharvester]

Re: Toshiba L500 blinking power LED

CPU 1.4v vcore is there so seems to be okay. I'll get round to updating the BIOS at some point.

Also, really odd thing - I touched a few inductors near the HDMI port in "blinking mode" and then the power light was stable. I only managed to make it do this twice and it doesn't do it now.

The problem may be +1.8v related - when powered up (both AC and battery together), the parts that are usually shorted read as having 1.8v, which quickly drops, and the motherboard powers off when it reaches 0v.

[degutji]

Re: Toshiba L500 blinking power LED

if you say so, try to reball HM55 Chip. I've done on HP & Toshiba last time with succeed after reball / replace that Chip

[spleenharvester]

Re: Toshiba L500 blinking power LED

I have no utilities to reball unfortunately and a light reflow did not work.

If anyone ever gets hold of either the full LA-5321P or LA-5322P schematic please let me know! I bet this one would be easy to fix if I had it!

edit: LA5322P here: http://zremcom.ru/scheme/scheme-tosh...-l500-la-5322p

[spleenharvester]

Re: Toshiba L500 blinking power LED

Okay further investigation shows the short to be on the +1.05VS AND +VTT line.

EDIT: I'm not sure I'm understanding this correctly:

http://i.imgur.com/bckjV67.png

It says VTTP become 1.05VS even though 1.05VS is generated by TPS51117?

Also, could that tantalum cap be shorted? (PC67)

[whaldsz]

Re: Toshiba L500 blinking power LED

Pull one leg of PL7 then test again to be sure. Or desolder PJ23.

[spleenharvester]

Re: Toshiba L500 blinking power LED

Mmm, think I will desolder PJ23, then PJ5 + PJ8 after. That should figure out whether the short's on 1.5VS or VTT.

[spleenharvester]

Re: Toshiba L500 blinking power LED

When battery only is plugged in (aka dead mode) the entire +1.5V non-standby line from APL5930 up to the G2992 controller reads as shorted.

With adapter and battery in, there appears to be no +1.5V or +1.1VSP from APL5930, but +5VALW is there.

PL7 which has been removed (see link)'s side closest to MOSFETs reads as a dead short to ground, whereas its opposite side reads as 12.7ohms. Is this normal or indicative of something?