Advent Monza S100(?) Dead No Power

[Topher_UK]

Hi, I've been working on an Advent Monza Red (I believe it's an S100, but the only labels on the unit say "Red") with broken screen brackets. Made sure it was disconnected, battery was out, grounded myself, and set to work. Only had to disassemble the base to attach the new hinges, in and out of there in 10 minutes. Everything is connected up properly, reassembled, and now - dead.

On A/C there are no lights, no response from power switch. Removed the battery, still nothing. Tried with battery only, nothing.

I've tried removing the battery and A/C and holding the power button for 2 minutes, I checked the CMOS battery, found it to be almost dead, and replaced it, still nothing.

The A/C adaptor seems to be good, checked it for voltage, all good. Tried another known good charger, just in case, still no good. Tried leaving it for 5 days untouched in case of a build up of static that needed to dissipate. Put it back together today, still dead.

I've pulled it apart again, tested the switch itself for continuity, disconnected everything and tried again. Ive checked for voltage from the DC jack along a few components, but without a schematic (or any real experience using them), I'm now at a loss.

The motherboard seems to have 3 different stickers with part numbers on, the only thing connecting the 3 is J141M

I'm assured that it was working when given to me (I really wish I'd checked it first - schoolboy error). The symptoms were a cracking sound when opening/closing the lid. As the plastic bezel around the screen was cracked at the points the hinges were broken, I assumed it was this. I suppose the cracking *could* have been the screen cable being damaged by the sharp broken edges of the screen brackets and sparking, although I see no sign of external damage to the cable.

Photos of the mobo attached. Any help would be much appreciated

[selldoor]

Re: Advent Monza S100(?) Dead No Power

I get a few hits using 76R-J141M1 off the bar code label

Have you checked the ram type is correct. Try it with no ram then just one stick. Try with no Ram no hard drive no dvd connector no wifi connector.
then try with just 1 stick of ram - nothing else - try in each slot.
Does the fan twitch at all? any lights?

Are you sure the new cmos battery is good - new?
Are you sure the adapter is the correct voltage/amps for the laptop?

[Topher_UK]

Re: Advent Monza S100(?) Dead No Power

Tried with no ram, each ram, both ram. Def the right ram, not been changed since new. I've stripped it down to the bare board, cpu, and heatsink. No lights, nothing.
Brand new CMOS battery - Duracell.
Original charger, seems to be good, and tried another known good charger

[selldoor]

Re: Advent Monza S100(?) Dead No Power

is there a light on the charger- does it stay lit when you plug into the laptop.


Where does the power go into the board cant see a barrel connector CN!3 ? and where does the button board connect

[Topher_UK]

Re: Advent Monza S100(?) Dead No Power

Green light on power brick, stays constant when plugged in.

DC IN and Button Board socket as highlighted

[selldoor]

Re: Advent Monza S100(?) Dead No Power

Ok I dont much about troubleshooting laptop motherboards but a starter might be to test that first component JP8 - (probably an inductor) small black rectangle.
Use your multimeter on 20vDC (assuming input is 19v?) Black lead on the ground screw H20 probe each side of the JP8 with red probe. Obviously need power to the board to do that - make sure the fan is fitted first.
Next component is 4835D Mosfet http://www.alldatasheet.com/datashee.../SI4835DY.html

You can test this for shorts without power to the board see here
https://www.badcaps.net/forum/showpo...4&postcount=19
for this test. (also lots of other useful tests)

[Topher_UK]

Re: Advent Monza S100(?) Dead No Power

JP8 - 19.13-19.14v either side.

My knowledge of testing MOSFETs is basic, so please bear with me. As we are looking at the picture, bottom row is Source pins 1, 2 and 3, bottom right is Gate, and top row is Drain 1-4?

Meter set to 200 ohms, -ve lead to S1, +ve lead to G closes the gate, then measure from S1 (-ve) to each of D 1-4 (+ve)? Then repeat from S2, and again from S3?

If this is all correct, every reading taken has flashed up a random number, followed by a "1" to the left, which I gather is an error. I clicked the meter up to 2k ohms, retested, and every single reading was 0.590

[Topher_UK]

Re: Advent Monza S100(?) Dead No Power

And I'm buggered if I have any understanding of why, but I've just pressed the power switch, and it's come on. Could something I've done earlier have unswitched the MOSFET, and by testing it I've somehow managed to reset it? Don't get me wrong, I'm made up that it's started working, but I'd like to know that a) it's not going to randomly pack up again, and b) what might have caused it in case I'm faced with something similar again

[selldoor]

Re: Advent Monza S100(?) Dead No Power

Well I dont know either - hate these sudden fixes- just as easily unfixed.

Maybe some residual voltage from the first test was enough to "reset" the mosfet in the second test- or perhaps something totally unconnected.

I suppose the real test is if you can switch it off and then on again

[Topher_UK]

Re: Advent Monza S100(?) Dead No Power

Off and on again a few times, battery is charging, have absolutely no idea. Like you say, it's annoying, as you can't say it's actually "fixed" if you don't know why it went wrong in the first place.

Incidentally, did I test the MOSFET correctly? What sort of readings should I have got? Would be nice if something useful came of this

[selldoor]

Re: Advent Monza S100(?) Dead No Power

Incidentally, did I test the MOSFET correctly? What sort of readings should I have got? Would be nice if something useful came of this

No you didnt really do it properly, though what you did was not wrong in this case
You are not testing the mosfet for anything other than shorts.
So there should have been no power to the board/mosfet.
Testing S1 to G1 is nothing to do with gate action it is just to test for shorts.

If you look at the diagram there is no D2D3 and no S2S3 as all the Ds and all the Ss
are connected internally and externally (all on the same trace/base) so test one you test them all.
Lesson is look at the diagram - not all 8 leg mosfets are the same.

If there was a D2 S2 and so on they would also be labelled as such on the datasheet.

As to the result - that was correct - only checking for shorts- so any result over 30 ohms is considered good.
Both the intermediary figure and 1 ( infinity or overscale) is good.
If it was below 30 ohms it may be bad -you would take off the board and re-test.

Hope that helps and doesnt sound critical.

[Topher_UK]

Re: Advent Monza S100(?) Dead No Power

Thanks for the input Selldoor. I guessed that the S legs were all connected, as well as the D, but like I say, it's all a good learning experience for me.

Very grateful for the time spent helping me with this