Toshiba S55T shorted

[Conste]

Hey there,

I have a new problem. Toshiba S55T - Board Petatron VGS Rev. 2.1.

Board doesn‘t get power, power jack is okay. I think because of a short the Board is shutting down.
Tried to give it a lower voltage than 19v with a laboratory power supply I have bought, but no power draw at all. Bridging the first Mosfets results in 0,2A power draw at 19v and an IC, I guess 3/5v regulator gets hot?
Could the KBC be the problem? It is an ITE 8587E.
Does anyone have a boardview?

Thanks in advance,
Constantin

[Techtiger]

Re: Toshiba S55T shorted

Need the Schmatic to help check for LDO5 & LDO3 is Generating from the regulator

[Conste]

Re: Toshiba S55T shorted

The IC which is getting hot is a TI 1225c, shall I desolder it?

Or is the problem a capacitor?

[lorins_core]

Re: Toshiba S55T shorted

Lots of Repair... Friend

Possible may be a Capacitor. but you need to Check the following.
but you need a Schema diagram.

Start on 19v rail... you can used LED light indicator that indicating totally Shorted

check have 19v. check fuse then coil on Main Mosfet then check the Mosfet...

must better used your Sense of Sight may some parts have Burn.

hoping can help you for little Part...

[lorins_core]

Re: Toshiba S55T shorted

Try this.

but you need an ASC opener program.

if you have can i Copy.

Here the Schema

[Conste]

Re: Toshiba S55T shorted

Try this.

but you need an ASC opener program.

if you have can i Copy.

Here the Schema

Wow! thank you Opened it with boardviewer, works fine.

How shall I start?

I also saw a Little spark when connecting the laboratory power supply to the unit, I guess the board is pulling amps and shuts down then because of short.
The unit which is getting hot is U8100, but I think this isn't for EC powering, but for further steps or am I wrong?

Fuses are good, no burned parts sofar. But Q8802 was changed before, I saw on soldering Job.

[Techtiger]

Re: Toshiba S55T shorted

test U8100 pin 3.12.13 6.20 for voltage

[Conste]

Re: Toshiba S55T shorted

Pin 3: 12,7 mV - nothing
Pin 12: 0,819V
Pin 13: nothing

pin 6: nothing
Pin 20: nothing

After Q8800 I only have those 0,819V like on PIN12.

[Conste]

Re: Toshiba S55T shorted

+3VA_DX has only 13 ohms - guess thats the reason of short.

I removed various parts - JP8108 / JP8101

Fuse after second Mosfet

CE8101 and U8100

Short on+3VA_DX not present anymore, Short on +RTC_Power also. I think TI 1225 (U8100) was the bad one.

Will bridge the fuse tomorrow solder a new EC inside.
After that, I will try to find a TI 1225 from a donor board maybe

[Techtiger]

Re: Toshiba S55T shorted

remove the cap C8101 and test pin3 U8100 short to GND if not trace it back
pin 12 shoul be +19V to turn on LDO3 LDO5 on U8100

[Conste]

Re: Toshiba S55T shorted

Cap 8101 and U8100 are removed, but I still don‘t have 19v on Pin 12

[Techtiger]

Re: Toshiba S55T shorted

Voltage in Q8802 all pins Q8800 all pins ? 123 4 5678 ?

[Conste]

Re: Toshiba S55T shorted

Q8800

Pin 1,2,3: 0,934V (drain)
Pin 4: 0,935V (gate)
Pin 5,6,7,8: 18,83V (source)

Is Pin4 too low or is something defective?

Q8802

Pin 1,2,3: 0,934V
Pin 4: 0,934V
Pin 5,6,7,8: 0,934V

[Techtiger]

Re: Toshiba S55T shorted

test the 2 Mosfets in Diod mode multimeter for short cannot tell exact N or P Channel
black Probe in S Red Prob in D Pchannel Value / Red Probe in S Black Probe in D Ncannel Value. (Is Pin4 too low or is something defective?)yes YOU dont'n have the gate pass in 1st Mosfet you have a resester and a Cap connect with the line tet them too

[Techtiger]

Re: Toshiba S55T shorted

if it's P Channel +3V in Gate if it's N +22V in Gate Pass

[Conste]

Re: Toshiba S55T shorted

Both MOSFETs show 0,14V in both direction. Also desoldered some more parts, but I don't get any process.
Guess I'll order one from china for 50 Euros

[Techtiger]

Re: Toshiba S55T shorted

test the 2 Mosfets in Diod mode multimeter for short
if not put a jumper remove Q8800 5678 (19V) connect pin 123 (19V) do you have a power bench first give 1V to see if it's passing

https://www.youtube.com/watch?v=yLffdWhBfFU

dont'n give up now

[Conste]

Re: Toshiba S55T shorted

Sometimes I had a short on 19V line and sometimes not, coil for 3,3V was getting hot then.
I then removed a Jumper and +3V_SYS was on short so I also removed many components...in the end I got a short everywhere…


Don't want to waste too much time on this one, since it has been soldered on it before me, so I will get a new one, it's better.

There are many more Motherboard to repair here