ACER Swift 3 SF314-52-52V8 dead

[mferna14]

Today I am working on an ACER Swift 3 SF314-52-52V8 dead (SU4EA Main Board). The history is that it's very clean & no sign of liquid spill & no short to ground rails. But all of a sudded it got dead. NO POWER AT ALL. On the First MOSFET Q8800 I get the 19v on the Drain but no output. On the Gate the voltage is 0.99... But according to this N-Channel FET the gate should be higher then the voltage applied to the drian, I am assuming it should be higher than 20v in order for the Drain & source to output volts. I checked BQ24735 where ACDRV is generated, it the same .99 volts. The test point on this chip VCC, LDO, ACDET seems to be fine but on ACOK I only get 1.6V which is low, guessing this volt should be around 3.2V being an OPEN Drain Output. Any tip or ideas what is going on with this would be a great help. Thanks in advance

[mcplslg123]

Re: ACER Swift 3 SF314-52-52V8 dead

Yes, ACOK should be 3.3V. Could be a bad charging ic itself but do check any components used as voltage divider for dc-in mosfets.

[mferna14]

Re: ACER Swift 3 SF314-52-52V8 dead

Thank you so much for the tip "mcplslg123"... Just want to ask you isn't this ACOK coming from the I/O chip... Anyway I will surely replace this chip & check. Do you think its the I/O chip??? just asking. Thanks

[mferna14]

Re: ACER Swift 3 SF314-52-52V8 dead

Replaced the BQ24735.. ACOK is still the same volt 1.6.. will check the divider now...ANy more tips will be a great help. Thanks

[SMDFlea]

Re: ACER Swift 3 SF314-52-52V8 dead

Replaced the BQ24735.. ACOK is still the same volt 1.6.. will check the divider now...ANy more tips will be a great help. Thanks

Test the D8801 dual diode and R8817

[mferna14]

Re: ACER Swift 3 SF314-52-52V8 dead

Both the D8801 dual diode & R8817 (22 ohms) both are 100% ok. No short & the resistor is giving the correct value... Any other tips. thanks

[mferna14]

Re: ACER Swift 3 SF314-52-52V8 dead

So now it was getting a pain in the a***., now it was time to act logically & find where the problem lies & why 19v is not passing through. First finding a short to ground. No visble shorts. Now since I was getting the input (Drain) of 19v on Q8800 & no output (Source), on the Gate it was just .99v whereas this volts should be about 24V in order for the MOSFET to turn on. First I removed Q8801 & R8808 so that if any volts present does not go to other components. Upon removing these I got the 24V on the Q8800 Gate confirming that the 1st step of BQ24735 & the I/O both are working fine. Then I put in the Resistor first & tested the other MOSFET Q8801. Guess what!!! the Gate & Source had a leak. Found a exact match MOSFET, soldered it in & all works fine. All the above voltages should be the same as assumed. ACOK came back to 3.2V & all other volts the same. Thanks for all the help & hope this trouble shooting helps someone in this world.