Understanding a laptop Schematic

[Aikiotto]

Howdy guys..

I wanted to see if someone could help me interpret this schematic (aspire one zg5) im basically trying to troubleshoot a completely dead notebook (no lights whatsoever of any kind).

In my very limited knowledge , laptop mobos do have some always presen signals (5v/3v) wich ive been unable to find on these lappies , in page 2 of the schematic those are identified as 3VPCU/5VPCU , based on that and since i cant measure it in any place im trying to pinpoint the IC responsible for generating these signals.

Question #1: would be IC ISL88731 (page 27) the one that generates 3VPCU? it should be present at its 11 PIN?

Thanks in advance to you for taking the time to read this!

[lucco85]

Re: Understanding a laptop Schematic

Go to the page below (28)
At PC75 should have 5VPCU on PC73 3VPCU
PC48 19V (VIN)
PQ2 pin 5,6,7,8 should have 19V
Check these voltages first

[Aikiotto]

Re: Understanding a laptop Schematic

Hello lucco , and sorry for my late answer i had no acces to the motherboard until today.

Theres nothing at those points you suggested , I even measured at all the close by coils (PL3 for 5VPCU and PL4 for 3vPCU) all are at 0v , so i started from the beggining and traced the 19v DCIN from the jack up to that "fuse" PF1 (Page 27) where im seeing VIN just on one side of it , nothing on the other , im assuming this one is open since theres no continuity either , or am i wrong trying to measure it mounted and treating it as a simple fuse?.

But something else puzzles me if the board isnt receiving any power (supposing the fuse mentioned earlier is actually open) why im measuring around 1.25v on one of the battery charger pins (the long one)???

Thanks again!

[budm]

Re: Understanding a laptop Schematic

Set your meter to 200 OHM scale (no batteries, no DC input to the laptop), put the probes on each end of the fuse and see what resistance reading you are getting, it should be less thane 1 Ohm, it sounds like you have blown main fuse.

[Aikiotto]

Re: Understanding a laptop Schematic

Hey budm

Well it definitly seems open (40 some Megaohm or just plain open on my autoscale meter) so its just as simple blown fuse as you mentioned, now to replace im looking at fast acting fuses right?

What kind of equipment should I use to replace this thing , I dont have any soldering equipment but have access to some of it (hot air station) at a friends place , so tips on how to do it are very welcome.

But again , if being the case of an open main fuse , how can i measure around 1.25v at one of the battery charger pins?.

Thanks for your input.

Edit:leave a small pic for the suspect in question.

[budm]

Re: Understanding a laptop Schematic

You are seein voltage with batteries installed. You do not even need to remove the old fuse, you lay the new one right on top if you have the clearance and solder the neds to the old fuse. You need to find out if the fuse is feeding shorted circuits first, this is not 100% test since the current may flow through some MOSEFT switches whic are normarly open (they turn on when power switch is activated). Set you meter to 200 Ohm scale and take resisitance readung between the ground (metal chassis, black probe), red probe to the end of the fuse that feeds the circuits and see if it shows real low Ohm reading. You can try regular fuse with leads to temporary test it. See the diagram to see what the fuse rating should be.

[Aikiotto]

Re: Understanding a laptop Schematic

Hello budm.

Well no , no battery just the ac adapter and the plain Motherboard without any component besides a single ram module and its CPU.

But anyway , i took your suggestion about leaving the open fuse in place and just applied a little bit of solder to bridge the gap (just temp fix while the replacement arrives "5A 32V fast acting smd fuse") and of course it worked , but now I just got a black screen wich probably means a corrupted BIOS , I will check that later.

Thanks for the suggestion.

[Subway Jack]

Re: Understanding a laptop Schematic

Hello budm.

Well no , no battery just the ac adapter and the plain Motherboard without any component besides a single ram module and its CPU.

But anyway , i took your suggestion about leaving the open fuse in place and just applied a little bit of solder to bridge the gap (just temp fix while the replacement arrives "5A 32V fast acting smd fuse") and of course it worked , but now I just got a black screen wich probably means a corrupted BIOS , I will check that later.

Thanks for the suggestion.

It was just the fuse? Did you get power to all the other power inductors (PL)?

[Subway Jack]

Re: Understanding a laptop Schematic

Go to the page below (28)
At PC75 should have 5VPCU on PC73 3VPCU
PC48 19V (VIN)
PQ2 pin 5,6,7,8 should have 19V
Check these voltages first

I'm a novice learning this stuff for work. I don't know why so I'll ask:

- Why did you tell him to check electrolytic capacitors for power vs the non polarized capacitors near it?
- Why didn't you have him check the PQ12 first?