My Pegasos 2 has recently started to turn itself on by itself.

The other day, I was in the same room when it suddenly powered itself up. Yesterday I arrived home to find it turned on but I am sure it was off when I went out.

The first time it happened, I started to use it and it mysteriously powered itself down after a few minutes.

I suspect the main power switch is faulty but it seems robust and in working order. This weekend I will take the case off and check connections etc.

Is there a chance that some on-board power sensor is at fault, confusing the PSU ?

If my Peg2 motherboard needs replacing I will definitely be in trouble.

thanks for any advice

koan

Bad earthing could, theoretically cause this, but there are many possible causes.

Check the following:
1) That the grounding cable (the "middle" one) on the PSU is really connected to earth (I have stumbled across some el-cheapo UPS that break this connection).
2) That the "On" switch is not shorting itself (moisture? rust?).
3) That the PSU itself is not dying or full of crap (moist dust/fur do not make great insulators). Check the stability of the voltage, especially on the +5V ramp and and +5V SB (pin 9 on the motherboard connector, color-coded purple IIRC).

If all of the above fails, you should perhaps contact a medium

Quote:

You've suggested what to check but could you enlighten me on the possible causes, apart from a broken power switch ?

Quote:

How could this cause the problem I'm experiencing ?

Here in Japan, power outlets rarely have an earth connection, I guess earth is floating for my board. It's never been a problem before though.

Quote:

I will check.

Quote:

The PSU is fairly new so it is less likely to be the source of the problem.

Thanks for the suggestions.

Quote:
The PSU relies on the PS_ON pin being brought to digital ground level to power itself on. If the earthing is not correct, charges can cumulate on the line depending on how the PSU is built (and the technology of the components; for example MOS is quite sensitive to stray charges since the oxide on the gate is an insulator) and the logic may detect a 0 when it is supposed to detect a 1.

This kind of problems usually become visible/more acute during winter time, since the air is dryer inside the homes (heating).

Quote:

Did you just mention that the PSU is fairly new? New as in "I've installed it shortly before the problems started"?

Quote:

Yes, considering my "heating" is air conditioning and it's snowing outside almost every day then that's possible. But as I said, there is no earth to ground connection.

I don't quite get your explanation: if static builds up then doesn't that stop the PSU from powering on ? I'm only an electronic engineer so I know little about power supplies.

(Added 26.02.2008) This doesn't really explain the power down I had the first time. I think I'm going with the broken power switch theory for now.

Quote:

New as in I installed a brand new one about 4 months ago and had no problems until just recently.

Thanks again for the help.

[ Edited by koan on 2008/2/26 21:51 ]