ACER 5742 Dead M/Board

[John McGivern]

Re: ACER 5742 Dead M/Board

Just another photo.

[John McGivern]

Re: ACER 5742 Dead M/Board

Photos of voltages.

[mcplslg123]

Re: ACER 5742 Dead M/Board

Your gate voltage at PQ51/52 is still wrong at 18v. it should be around 6-8V. Unless that is fixed PQ52 wont pass 19V to P3(Thats your B+ line). So effectively you are having 6V instead of 19V at B+ line. So laptop will not turn on.

[John McGivern]

Re: ACER 5742 Dead M/Board

Mcpisig Techtiger has been helping me with this laptop and has already explained this to me, can you suggest what may be causing the problem???

[mcplslg123]

Re: ACER 5742 Dead M/Board

PQ56/58-Either one of them or both may be faulty in my opinion.

[John McGivern]

Re: ACER 5742 Dead M/Board

Hi mcpisig123, thanks for replying, I will wait till techtiger gets back to me as he has been my main man, many thanks.

[Techtiger]

Re: ACER 5742 Dead M/Board

PQ56/58-Either one of them or both may be faulty in my opinion.

Hi mcpisig123, thanks for replying, I will wait till techtiger gets back to me as he has been my main man, many thanks.

check those PQ56/58 as mcplslg123 have requested

[mcplslg123]

Re: ACER 5742 Dead M/Board

Yes, its always wiser to get more opinions and@techtiger has been helping a lot of people in the forum. keep up the good job@techtiger.

[John McGivern]

Re: ACER 5742 Dead M/Board

techtiger mcpisig123, thank you for helping. I haven't had time to remove pq56/58 I tested them in circuit and seem ok. When I removed pq52 I tested pads and they are shorted to gnd. I think B+is shorted. See photo these caps all show the lowest ohm reading 28ohms dont know which one or more. the 2 large caps are marked C1 and C2 but I cannot find them on the schemeatic. I found 4 more same value tested them in diode mode red to gnd black to cap these measure very low compared to the same value caps 252 to 31. The large caps are 10uF 25v (1206) Silly question which are likely to fail first???
I cannot find what line all these caps in photo are on.

[mcplslg123]

Re: ACER 5742 Dead M/Board

C1/C2 caps are connected to +VGA_CORE(page25). The 7 small caps placed together-3 on the right side seems in bad shape as per your pics. can you remove them and test out of circuit. Btw, this is part of cpu vrm circuit-so low resistance is expected.

[John McGivern]

Re: ACER 5742 Dead M/Board

All 3caps are ok. Do I need them.

[John McGivern]

Re: ACER 5742 Dead M/Board

Removed pc248 same voltage on pq drain 6.24v replaced pc248, removed pc249 voltage on drain same. Only pq56 and 58 to replace but I think these are good.

[John McGivern]

Re: ACER 5742 Dead M/Board

Disaster pc248 ping lost 0402 package.
Does anyone know where to buy cut reel smd caps or acer 5742 cap selection pack??? UK
I could have bought a used m/b cheaper than what I have spent on this M/B but I am determined to repair this plus it's a good learning process. The really frustrating part is acquiring parts and waiting for them to arrive, many thanks, John.

[mcplslg123]

Re: ACER 5742 Dead M/Board

MB should work even without PC248

[mcplslg123]

Re: ACER 5742 Dead M/Board

Disaster pc248 ping lost 0402 package.
Does anyone know where to buy cut reel smd caps or acer 5742 cap selection pack??? UK
I could have bought a used m/b cheaper than what I have spent on this M/B but I am determined to repair this plus it's a good learning process. The really frustrating part is acquiring parts and waiting for them to arrive, many thanks, John.

You can get plenty of those caps from scrap mb. Dont you have one??

[John McGivern]

Re: ACER 5742 Dead M/Board

Unfortunately no how crucial is cap value I have board from hard drive with similar footprint but difficult to measure cap value mcpisig123 I changed pq56 Will change pq58 they are difficult to desolder due to other components being so close this board has large copper traces and requires a lot of heat even removing small packages and my skills are lacking a bit when trying to remove 0603 and 0402, thanks for advice, John.

[John McGivern]

Re: ACER 5742 Dead M/Board

Hi, changed pq56 applied 3.3 and adapter. One side od pr371 is 3.3v other side is 0.290v this is pq59/63 gates. 19v pq51 and drain of pq52 source is still 6.24v and pq52 still removed from board.
Merry Xmas and a Happy New Year to all Bad Cap Members.