Replacing A5sHB transistor (netbook)

[Paligap]

Hi everyone, Im trying to repair a generic chinese netbook that has a WM8850 CPU and a VT1603A and for which I couldn't find the schematic as it has no brand printed anywhere whatsoever.

This netbook won't turn on, the leds of the battery, etc., start blinking once I connect the power supply.The battery charges well, but it's not recognized by the leds. The volts are very unstable all over the board.

I think one of these transistors A5sHB (I have three of those near the jack of the power supply, one near the battery and one amidst a few diodes in the middle of this circuit path) is damaged because it measures continuity between its pins, but Im not sure.

What you guys recommend me to do? Im not getting one of these transistors to try and see if that was the issue and I don't want to try without the damaged one.

 

[dorke]

Start with posing a clear photo of the board.
and the voltages you measure ,mark where on the board you take the measurements.

 

[Paligap]

Start with posing a clear photo of the board.
and the voltages you measure ,mark where on the board you take the measurements.

Okay, thanks for the reply, I'll post a picture latter, but there will be no need to point out where I make the measurements, because it varies from the start, meaning the pins of charge of the jack where I connect the power supply, going through the capacitors, all over to the battery.

 

[Paligap]

- If I connect the DC adapter (5v - 2A) plus the battery and measure the two pins of the battery, voltages go from 4v to 1v constantly.
- If I measure from the + pin of the jack to GND voltages shows the same as the battery, from 5-4 to 1-2-3v constantly. The adapter works fine.
- If I measure GND to any component near the jack and the battery, voltages -some of them a bit lower than others, shows unestable in the same way.

- If I only connect the battery and do the same measurements, voltages are stable, but the battery is not recognized by the led as they simply don't turn on as when I connect the adapter and the battery is charged.

PS: there's a resistance gone from the board and a capacitor that I wanted to measure properly, Im gonna put both again later (they were working fine, though of course I don't know the specific value of the capacitor as I don't have the schematic).

I'd appreciate any help, Im about to give up on this board and use it as replacement, so I'll try anything at this point, it doesn't matter.

 

[dorke]

Your transistor is probably a P-channel Mosfet
Si2305DS.

From post #1 :"The battery charges well".
This is strange, because you also say the battery voltage drops to 1v and fluctuates with the DC Adapter at post #3.

With a charged battery only.
check the voltages through those Transistors,
what do you get?

 

[Paligap]

 

[dorke]

Please trace the voltage of the battery with an omh-meter(with the battery out) till it gets to the 3.79 voltage on the top Tr.

Try to identify the trace of the DC adapter voltage on the board with an omh-meter as well.

Please post two separate and clear(so that the device markings are readable) photos of the two squared areas in green and pink.

 

[Paligap]

Do you mean with the multimeter on the ohm scale?

 

[dorke]

Yes

 

[Paligap]

Don't know how to do that

 

[dorke]

Don't know how to do that

It is just measuring resistance from the battery and the Adapter connections to points in the circuit.
if you get zero ohms reading than those points are shorted i.e connected.
watch this ,it may help(4:40 on).

 

[Paligap]

Okay, thanks again for the help and the patience man. Let me see if I can get this clear.

Isn't this just another way of measuring continuity? What's the difference between both? What does it means if it measures way more than zero ohms between two points that are connected, can this happen?

I got to do it with the adapter connected?

As I need to read close to zero, I'd need to use my multimeter on the scale of 200 ohms?

 

[Paligap]

Part B from the board

- Green is the negative pin of the battery. Does all its way to the negative pins of the jack.

- Red is the positive pin of the Jack

- Pink is this point of prove near the battery called VIN0

- The positive Pin of the battery doesn't measure anything on this part of the board

 

[Paligap]

Part A from the board

- Red is the negative pin of the battery. Does all its way to the negative pin of the jack.

- Green is the positive pin of the battery.

- Pink is the positive pin of the jack.

 

[Paligap]

It seems like the trace of the positive pin of the jack does look suspect, am I right?

 

[davenn]

What does it means if it measures way more than zero ohms between two points that are connected, can this happen?

it means those 2 points are connected with zero Ohms resistance

I got to do it with the adapter connected?

no, disconnected

 

[dorke]

Before we continue,a few questions:

1.What is the rated battery voltage and current and type?
2.Is it the "original one"?
3.How many contacts those it have?
4.A clear photo of the battery please.
5.Is the adapter the original one?
6.Anything written on the adapter socket on the netbook?

 

[Paligap]

1. The battery voltages are: 3.7V / 3600mAh
2. According to the owner, yes.
3. Two

4.


5. According to owner, yes.
6. Just DCIN

Picture of the adapter:

 

[dorke]

If you connect a fully charged battery alone without the adapter.
what is the voltage you measure on the battery terminals?
and along the battery related traces pink-line and green-line?

 

[Paligap]

Fully charged battery measures 4,12v on its terminals.

Pink-line doesn't measure anything.

Green-line measures 4,12v on all its traces.