Medion MD42200 does not power up

[KG21]

Hello badcaps members,

I hope you can help me. I have a Medion MD42200 motherboard in front of me and it does not power up neither with ac adapter nor battery.
If I press the power button on the laptop the power led lights up just for a half second, the fan always doesn't turn on and then the laptop powers off.
I checked the AC Adapter and the DC In Jack of the laptop and both are ok.

I read to check for bad capacitors or hot mosfets I should use a variable power supply with 1.5V/1A, but I only have a universal ac adapter with the lowest voltage of 12V and the laptop needs 19V. Could I give it a try?

Then I also checked the voltages of the Maxim ICs. According to the datasheets the output voltages are correct. Then I looked after bad ceramic capacitors but there are none.

I don't know what else I can do to fix the problem. I don't have the right medion laptop schematic, just a sample medion schematic diagram from laptop-schematics.cxm. Perhaps someone has a md42200 schematic diagram for me and as well a hint

Thank You

KG21

[PCBONEZ]

Re: Medion MD42200 does not power up

Medion are made by someone else and Medion 'slaps their name on it' so to speak.
See if you can figure out who made it and look up that. - This can give more info on known problems.
.

[KG21]

Re: Medion MD42200 does not power up

I looked it up and the result was that the Medion MD95101 has the same motherboard in his system.

On the motherboard is written:

HannStarJMV-4 94V-0
0436632
MD1 M/B
48.46P01.011

I know Hannstar makes also Mainboards for Acer, Gateway, Mitac etc. But if I google the part nr. 48.46P01.011 with gateway with gateway or mitac I don't get an equivalent motherboard as result.

Is there another possibility to do something?

[PCBONEZ]

Re: Medion MD42200 does not power up

First see if it will boot with all drives disconnected. [Shorted drive motor can kill power.]
Next try with one RAM stick at a time [and switch].

If that doesn't work you will have to start tracing circuits starting from where the power goes in until you find the defect.

If you aren't good with electronics then replace the board -or- find one that boots with a bad screen on ebay and build one from the two.
.

[KG21]

Re: Medion MD42200 does not power up

First see if it will boot with all drives disconnected. [Shorted drive motor can kill power.]
Next try with one RAM stick at a time [and switch].

I have done that. But no success.

I'm not very good at electronics. If the board would have a bad video card, I had made a reflow and done. I found a board on ebay but I don't want to pay 50 euros for it.

If that doesn't work you will have to start tracing circuits starting from where the power goes in until you find the defect.

I looked in the sample schematics that I have and I think my motherboard is a little bit equivalent to the schematics one. It uses almost the same Max ICs. Maybe I find the way of the power to the defect.
I asked in my first post whether I can use the my universal adapter with an output voltage of 12V dc to find a hot/defective mosfet or something else?
What else can I check on the baord without desoldering e.g. a cap and check for short circuit? Do always have resistors or fuses a positive continuity (in form of beep from DMM)?

[PCBONEZ]

Re: Medion MD42200 does not power up

Max ICs are a known problem in some other laptops.
- I only know because I've seen it mentioned here several times.

You might try searching the forum and see if anything looks similar.
Might also gather some tips on how to test them.

I did refurbish laptops for a while but I never got into repairing laptop motherboards [if the board is blown I'd part the machine out to fix others] but there are a number of people here that are quite skilled at that.
.

[PCBONEZ]

Re: Medion MD42200 does not power up

Oh and, when the lappy techs wander in the first thing they will want is photos.

[KG21]

Re: Medion MD42200 does not power up

Here I made two pics of my board:




the second photo shows red circled 8 pin chips. I don't know if they are MOSFETs. But they have a temperature over 50°C right after I plugged in the ac adapter and the videochip gets hot, too. Could they be defective?
Also the power LED lights up if I plug in the ac adapter and then the Laptop turns off themselves, all without pressing the power button. This isn't normal.

[PCBONEZ]

Re: Medion MD42200 does not power up

Punch numbers on IC chips into google and see if you can find the data sheets.
Then using that and what you see on the board draw out the circuit.
.

[mattbrad2]

Re: Medion MD42200 does not power up

You have a digital volt meter? A 'U' designation usually isn't mosfet but the 2 on the right sure do have the pin outs for them. The one on the left could be a dual channel I suppose but its hard to read the part number. Put your meter in diode mode and place each probe in between the 2nd and 3rd pin on each side. Check one a a time and also reverse the leads and repeat the check. Report back here what you find. These are probably good - more than likely you have a shorted ceramic cap or another shorted mosfet by itself. That temperature reading indicates those fets are absorbing too much current, either because they are being grounded or their internal diodes are shot.

[KG21]

Re: Medion MD42200 does not power up

thank you for your answer mattbrad2.
I will check it on friday and yes I have a digital volt meter. I tried to get the datasheets for the three components but didn't find anything.
Here are the part numbers:

left component circled: APL S331 BG7CH --> could be a dual channel because of the "CH"?
right components circled: should be both 4407 BE4S13 and have a symbol on it is something with an "A"

I tried to find those components at alldatasheets.com but without success. Maybe you can find something.

[KG21]

Re: Medion MD42200 does not power up

the right circled components are: AO4407. the company is alpha & omega. I found it. But the APL component is still left.

[b700029]

Re: Medion MD42200 does not power up

Anpec APL5331 3A Bus Termination Regulator
http://www.alldatasheet.com/datashee...C/APL5331.html

There is a short somewhere.

[KG21]

Re: Medion MD42200 does not power up

thx b700029. it was really a "5" not an "S".

I could not wait until friday so I already have checked the board.

Firstly, I made a mistake with the red circled components. The real numbers are for U26: AO4422 BD4K23
and for U27: AO4406 BD313V.

I've got the following voltages for U26:

Source (pin 1 to 3): 2.7V
Gate (pin 4): 3.52V
Drain (pin 5 to 8): 18.63V --> the AC Adapter delivers ca. 19V

diode test with Multi Meter:

2pin <-> 2pin: infinity reverse: ca. 505
3pin <-> 3pin: infinity reverse: ca. 505

for U27:

Source (pin 1 to 3): 0V
Gate (pin 4): 4.22V
Drain (pin 5 to 8): 2.7V

diode test with Multi Meter:

2pin <-> 2pin: 403 reverse: 178
3pin <-> 3pin: 403 reverse: 178

Could be U27 defective? If yes, can I remove the component from the board and check the board with the ac adapter or at first replace U27 with a new one and then test the board?

I also checked the APL5331. All voltages are in the recommended range according to the datasheet.

How can I check the parallel caps C197 and C198? Do I have to desolder them and then can I check it for a short? I tried to check them with the ohmmeter of my multi meter and they go in both directions with the probes to infinity. They should be ok, I guess.

[mattbrad2]

Re: Medion MD42200 does not power up

U26 is fine (mosfet should read infinite in one direction - it's internal diode is working properly)

U27 however is reading wrong. This could be a false reading from a short somewhere else on the board so to rule that out you'll need to lift at least one side of U27 off the board and re-test (test it out of circuit).

Caps shouldn't trigger your continuity test (well maybe for a second until your dmm charges it). An ohm or diode test should start at a low value and steadily work upwards (as it charges, its resistance changes). Do the same with these caps - lift one side and re-test. You'll need some good solder skills for this so I'd probably test on some other board you may have lying around first. Remember, in parallel, if one cap is shorted, the other will also read shorted if tested in circuit. This is why lifting one side of a component is the better method of testing.

Also, a word of warning - lifting mosfets can be extremely tricky. It will require both hands and something to "pry" one side up while you are heating it with an iron. Prying a hot mosfet can cause all sorts of damage to the fet itself or worse, lift the pads off the motherboard. Be very, very careful with this.

[KG21]

Re: Medion MD42200 does not power up

U27 however is reading wrong. This could be a false reading from a short somewhere else on the board so to rule that out you'll need to lift at least one side of U27 off the board and re-test (test it out of circuit).

Remember, in parallel, if one cap is shorted, the other will also read shorted if tested in circuit. This is why lifting one side of a component is the better method of testing.

It sounds like the videoclip test capacitors from prehertech that I watched on youtube yesterday
Maybe I could use my hot air gun to lift U27 and one capacitor from the board? The solder should melt at around 180°C, I guess.
I hope I can find then the cause of the problem.

[KG21]

Re: Medion MD42200 does not power up

Well, I lifted at the Mosfet U27 one drain and one source leg. That was the 2pin/2pin. The results are the same like before.

diode test again with Multi Meter:

2pin <-> 2pin: 407 reverse: 186
3pin <-> 3pin: 407 reverse: 186

So the Mosfet AO4406 is defective, because it does not have an infinity, right?

I also lifted C198 and it is as you said. Both capacitors showed in the continuity test that the resistance increases and finally the multi meter showed an infinity.

[mattbrad2]

Re: Medion MD42200 does not power up

You'll need to lift one side completely. The 4 drain pins are all in parallel so lifting just one won't do you any good, unfortunately.

[KG21]

Re: Medion MD42200 does not power up

I lifted the pins 1 to 4. So three sources and the gate and one drain (pin 7) is lifted. If I check the MOSFET now, my mutlimeter will show me a 478 and 1041. There is no infinity.
I also made a mistake at the first pin. The leg did not break but it is not attached to the MOSFET anymore. Now I can really purchase a new one.

[KG21]

Re: Medion MD42200 does not power up

today I desoldered the MOSFET and the diode test showed in one direction an infinity and the other direction 536.
Where could I also look for a defective component on the board?