Prev: Component NSKE 115 .1+120 ohm 350 VAC NISSEI E
Next: Philips Plasma TV 50PF7320 help needed
From: Mike De Petris on 13 Aug 2010 16:05
On Aug 13, 9:13 pm, Meat Plow <mhyw...(a)yahoo.com> wrote:
> > Anyway I can still use the laptop on battery, or giving 12V with an ATX
> > PSU in place of the positive battery pole, leaving other battery
> > contacts in place.
>
> Usually those things run off a 19 volt 95 watt PSU.

yes of course, but this motherboard does not like it any more, 12V
from the battery (or external, faking the battery connector) is still
ok instead

From: whit3rd on 13 Aug 2010 16:19
On Aug 13, 9:25 am, Mike De Petris <mikedepet...(a)gmail.com> wrote:

> ... the laptop is completely teared a
> part, non problems of air flow, and when connectinh power it locks
> immediately even if in the BIOS pages

There's a second CPU (a little tiny one) that handles the power
sequencing. The 'BIOS pages' are only for the big CPU, it's that
little battery-monitor one that runs into some kind of trouble, and
it has that problem every time the external power is applied and
it tries to do the natural thing, run the computer from external
power and charge the battery. Somehow it senses overvoltage
or overcurrent and shuts down.

Look for small-value current sense resistors that are open, or
for semiconductor switches that are shorted (can't turn off).
There are often PMOS power switch transistors involved.
Also, look for fuses (they might not LOOK like fuses, though).

Battery charge current might be channeled through a switchmode
regulator, those have always had problems if a capacitor fails.
From: Ken on 13 Aug 2010 17:25
Mike De Petris wrote:
> On Aug 13, 9:54 pm, Ken<K...(a)invalid.com> wrote:
>> Have you looked at the MB power bus (+5v I would assume) for ripple
>> when you attach the external power supply?
>
> this is what I am asking for, I tought I should measure it at the
> socket pin holes, how can I idetify the +5V line on the motherboard?
>
My guess is the hard drive is operating on +5v. You could measure it
there.

> And how would you measure (and fix the cause) a ripple on the bus? I
> have a couple of scopes and multimeters for that, but how?

First determine if it has ripple. You can normally take a volt meter
set for AC and measure the ripple on a DC bus. Old VOM's used a cap to
isolate the AC from the DC component, but the new DVM's generally work
for this. If you did find ripple, look for a cap that is bad or
possibly a diode that is shorted. First determine if it exists.
From: larry moe 'n curly on 13 Aug 2010 20:47
A schematic of the Toshiba A205 series can be found in this forum:

www.reepair.net/en

Here's a really good website about Toshiba laptops:

www.IrisVista.com

First  |  Prev  | 
Pages: 1 2 3
Prev: Component NSKE 115 .1+120 ohm 350 VAC NISSEI E
Next: Philips Plasma TV 50PF7320 help needed