Help wit Acer 5740 Board [All pins on AC Socket shorting]

[DJ_MIX]

Need help with a Acer 5740 board I picked up:
Symptoms when received:
- 1 Would not power on with AC only (Ac Adapter (PS) light flickers NOT STEADY)
-2 Powers and posts on with battery only
3- Worked with AC and Battery pluged in but no charge light

I was thinking AC Plug so I removed it but I see not shorts in plug

Then I go ahead and do a Continuity test on pins on ac Adapter on board and
have weird results:

All pins ground / mounting holes and POsitive pin all show they all connected to each other. I believe Positive should not show up as connected to ground pins correct?

How do I go about fixing this and hat is the cause? is it damage to traces on board at ac adapter connector or other componets.

[spidey]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

i think the problem is protection circuit. check schematic, in charging circuit there are 2 mosfets connected together, where B+ comes. one of them is short.

[DJ_MIX]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

i think the problem is protection circuit. check schematic, in charging circuit there are 2 mosfets connected together, where B+ comes. one of them is short.

I'm new to this:
I found the schematic attached:
Should I be looking at U29 & U38 or

is it these two U35 & u32

Also how do I test these fets do I need to remove them and then test what.

Thanks

[DJ_MIX]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

I think I found the problem, maybe someone can confirm

While checking U32 & U35 (FDS8884-GP IC)
U32 Pins 1 & 4 give me a 5.2 reading when set to Ohms (20K)
U35 Pins 1 & 4 give me 1 (no reading) which is correct should be no flow from source to gate

Can anyone tell me how to test mosfets for shorts Links?? must removed or can be tested on boad with no power source?

[fddizon]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

test pin 1 to pin 8..

reading should be one way. (on board, set to diode test mode)

[DJ_MIX]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

test pin 1 to pin 8..

reading should be one way. (on board, set to diode test mode)

I quickly tested both U32 & U35

and can confirm that I only get readings 1 way on both chips.

Going to test remaining fets when I get home.

[DJ_MIX]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

I'm certain it's U32 & U35
THey only get flow in one direction but Pin 4 (Gate) should be close but getting flow

Now schematic has U32, U35 FDS8884-GP
But actual chips on board are 4800B
Should I still use 4800B or get FDS8884 mr ether will work

[cyberhack]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

in picture 1 the 4 mosfets in arrow the first looks damaged

[DJ_MIX]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

in picture 1 the 4 mosfets in arrow the first looks damaged

Sorry don't see any damage at all to the board besides me removing ac plug..

[whaldsz]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

Check voltages of U29, ACOK, ACIN, DCIN of U30.

[DJ_MIX]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

Check voltages of U29, ACOK, ACIN, DCIN of U30.

I'll give that a shot but, it may not work since I get a short right at ac socket. I even tried removing socket and using my variable power supply and crank it to 18V but only see it supply about 1.X volts.

I removed U32 and u35 becuase they look like they might be bad but afther tesing it outside board they appear fine.

[DJ_MIX]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

I give up on this board I supply it 18V with regulated power supply and only get

.14v at ac socket Pins.. Thanks for everyones suggestions u29 gets about .14v as well
but ac in dc in I get not readings

Works fine on battery and also get good readings on U35 and u32 with battery

[dj_ricoh]

Re: Help wit Acer 5740 Board [All pins on AC Socket shorting]

if you have any boards to take some parts out change RT8206BGQW and it will be ok.
i had a samsung notebook and it was supply with 24V and it was running for a week; after it will only work with battery on and charger; if you took out the battery it will not start no power no light, nothing( the battery was not charging)