Doesn't power on - Is this system dead? (Medion PC) 1

[Einheri]

The PC:
Medion tower
Motherboard MS-6716 (special mobo made for Medion)
Sound, USB, Network, card readers, on board
CPU: AMD Athlon 2000+ (1.67GHz) socket 462
RAM: 256Mo DDR - PC2700
PSU: 250W

The problem:
The PC doesn't power on.
No one movement of the fan, and no one beep.

What I have already done:
Cleaned carefuly the 2 sides of the mobo,
no clue of defective capacitor or overheated area.
Removed and cleaned the heat sink, and fan,
Cleaned and resited the CPU with fresh thermal paste,
Cleared the CMOS
Remove the battery cell for hours
Tested the RAM OK with Memtest86,
Tried a spare PSU
But still no power up, except the CPU's fan at an only condition:

The symptoms (same in following situations):
1.- mobo and CPU & fan without anything other
2.- the same plus RAM
3.- the same plus RAM & video card
4.- all 3 cases as below, but without the battery cell
If the power connector of the PSU is inserted correctly and locked in the mobo: nothing happens, even a beep.
If I power the PSU, and slightly insert the connector in the mobo, the fan starts and runs, and I get sometimes one click (not really a beep), or sometimes looping clicks without end.
At this moment, if I press the connector to sit it down at it's right place, the fan and the beeps stop.

I would be grateful if someone could help.
Thanks in advance.

Don't tell me that Medion is bad: I nowaday know that, but I didn't when I bought it 3 years ago.

 

[franklin97355]

Have you tried a different power supply? (my first choice)
When you had it out of the case did you short the pins on the motherboard to start powerup?

The answer is "42"

 

[Einheri]

Thanks to franklin97355. It's a good idea. It didn't work for me, but it's a valuable tip.
Today, a friend came home with some spare parts, so ,we could test that PSU is good, and CPU is good, as they work well on an other mobo.
Finaly, I think my mobo is dead.
Or, I'm too stupid to find out the problem.

 

[stduc]

You are probably on a hiding to nothing with this one. But the fact that the CPU tries to start as you plug in the power and then stops as you fully insert the power is a good clue. It raises two possibilities in my mind as the likely cause.

The main board power socket could be faulty. Possibly a dry joint?

Something on the mob is shorting?
With the plug partially inserted and the CPU fan running, some pins in the power socket are probably not contacting. But power is getting to the CPU fan and probably the CPU. After insertion and all pins connected I suspect that some component on the mobo is causing the voltage to drop by draining an excessive amount of current.
The most likely culprit is a capacitor. I suggest you reinspect all capacitors for signs of damage. Unfortunately many other components could potentially have short circuited as well.

It is possibly just worth the effort of re-soldering the main socket, re-inspecting the capacitors and double checking the board for any clues. If that doesn't work then you need a mobo tester - which is obviously an impractical suggestion at home. I suppose you could try leaving it powered up for a while and see if your fingers can detect anything getting hot that shouldn't? (I guess you don't have a thermal imaging camera?)