Acer 7736zg No power

[bollin]

Re: Acer 7736zg No power

Ok, let me clarify things. Firstly, I got the 1.8 volt reading before I replaced anything. Then I replaced the fds8884 and still got 1.8 volts.
Secondly, I started to suspect the ISL62392 and when I was reading voltage in I slipped with my probe and it got fried. My mistake, as I mentioned earlier.
So, now I have to wait for my replacement isl62392 to continue troubleshooting.
Hope you are a little less confused now.

[bollin]

Re: Acer 7736zg No power

can you tell me, you have 1.8v after pressing power button or before ?

Nothing happened when inserting the power supply or pressing the power button. All voltages that i have measured are with power supply plugged in. At first I had 3 volts on the power button, but since I accidentally fried the isl62392 I haven´t got that.

[spidey]

Re: Acer 7736zg No power

You can not get 1.8v if there is no 5v and 3.3v.

[bollin]

Re: Acer 7736zg No power

No, and I don´t as it is now. I did get it when the isl62392 was still working.

[spidey]

Re: Acer 7736zg No power

ok, after you solder it we continue

[bollin]

Re: Acer 7736zg No power

Ok, so I got the replacement today, and soldered it in. When I plug it in, the power supply goes crazy and the isl62392 gets very hot. I don´t quite know what went wrong. I was a little bit sloppy with ESD, so that might have broken it. Now I have to order another replacement...

[bollin]

Re: Acer 7736zg No power

Today I got the replacement, and as I had the "broken" one desoldered I decided to do some testing. First I checked if the short on dcbatout was still there, and to my surprise it still was! So I started checking caps between dcbatout and ground, and so far I have found none that is bad. There are quite a few to check, so I decided to leave that for the moment and check the 5v and 3v rail for shorts. Turns out that the 5v line was shorted, so I desoldered the coil, and found the short to be at u58. After I removed it it seemed like the short on dcbatout was gone too. I found a replacement from another board, and soldered it in, still no short. Soldered in the new isl62932 and checked again, still looks good. I let it cool, and plugged in the charger, and again it goes in to short circuit protection. And the short is back. I´m running out of ideas here...

[bollin]

Re: Acer 7736zg No power

I removed U64, and now dcbatout is at 18.64 volts, AD+ is at 19.22 volts. No 3d3v_s5, 3d3v_aux_s5, 5v_s5 or 5v_aux_s5. I have ordered new fets for the 5v and 3v rails. There is probably one or more defective fets on those rails, and perhaps that is why it won´t work and that the dcbatout is at 18.64 volts instead of 19.22 that it should be.

[Tuomo]

Re: Acer 7736zg No power

I removed U64, and now dcbatout is at 18.64 volts, AD+ is at 19.22 volts. No 3d3v_s5, 3d3v_aux_s5, 5v_s5 or 5v_aux_s5. I have ordered new fets for the 5v and 3v rails. There is probably one or more defective fets on those rails, and perhaps that is why it won´t work and that the dcbatout is at 18.64 volts instead of 19.22 that it should be.

Can measure U62 pins?

[bollin]

Re: Acer 7736zg No power

I can measure the U62 pins, but since there are no voltages present at all (except dcbatout) it is probably bad. Before I measure pins I will check for shorts on 3d3v_aux_s5 and 5v_aux_s5. If there aren´t any shorts, I will replace it and measure pins then.

[bollin]

Re: Acer 7736zg No power

Ok, I have found some time to work on this thing again, and made some progress. Turns out that the 3d3v_aux_s5 was shorted, and I believe that the KBC is the cause of that. I removed it and the resistance is now at a more "normal" level. So, I will order a replacement for it.
The 5v_s5 is still not good, and I don´t know where to look for problems since I haven´t got the right schematic for it (I desoldered the coil and found that the problem is probably on some IC powered by the 5v_s5 rail). I only got the DDR2 version where the power sections is the same when it comes to the 3v/5v rails, but on the others it (of course) different. Anyone got the JV71 DDR3 schematic?

[bollin]

Re: Acer 7736zg No power

I found dthe schematic, back to work.

[Francisco.s]

Re: Acer 7736zg No power

Can you upload the new schematic?

[bollin]

Re: Acer 7736zg No power

Yes, here it is

[Khron]

Re: Acer 7736zg No power

[EDIT: My bad... )

[Francisco.s]

Re: Acer 7736zg No power

Time for a reflow?

First try to reprogram bios chip. (U19) (MX25L1605D)
Could be it has some corrupt data.
Good luck.

[Francisco.s]

Re: Acer 7736zg No power

[EDIT: My bad... )

¿?

[stealth]

Re: Acer 7736zg No power

hi guys just wondering if you got this working or not ? I have the same JV71-MV motherboard with same problem with ticking sound and no LEDs at all.

[bollin]

Re: Acer 7736zg No power

I haven´t got it working yet. It has been on the shelf now for a while, but last week I decided to attend to it again. So I have ordered some parts and now I am fairly confident that I will get it working again.

My advice is to check U58, U59, U63 and U64.

[bollin]

Re: Acer 7736zg No power

Now I have finally found the time to start this project up again. Today I started checking it again with my dmm, and found that 1d5v_s3 is shorted to ground. 3d3v and 5v also looked suspicious, but that is something I will look at later.
I removed coil L58, and found that the short is after the coil, so I kept on removing IC:s that could be at fault, but the short didn´t go away. I removed U54, U69 and U74 but the short was still there on the 1d5v rail.
Anyone got ideas where to look next? Checking caps?