Machine not powering on?

[ChrisB]

Hey all,

Got an eMachine T2642 , Machine is not powering on at all. The power
supply reads 150W, 250W max. Ive tested 3 different power supplies, 2
375W max, and a 280W max. Still no dice. The leads seem to be fine as
well. Any idea what is going on here?? Is it alright to test this 150W/
250W max PS in another machine? or would it fry the board/machine if I
test it?? thanks guys!

 

[Paul]

Hey all,

Got an eMachine T2642 , Machine is not powering on at all. The power
supply reads 150W, 250W max. Ive tested 3 different power supplies, 2
375W max, and a 280W max. Still no dice. The leads seem to be fine as
well. Any idea what is going on here?? Is it alright to test this 150W/
250W max PS in another machine? or would it fry the board/machine if I
test it?? thanks guys!

But consider the evidence you've collected so far.

Since replacement PSUs are not doing anything, it would seem the eMachine
PSU has damaged its motherboard. Transferring a "known dangerous" PSU
into another machine is just asking for trouble, in the form of a damaged
second machine.

It is possible to "jump start" a PSU, by connecting PS_ON# to an adjacent
COM/GND pin. That bypasses the PS_ON# logic on the motherboard, and should
cause the PSU fan to spin. PS_ON# is open collector, which is why you can
safely jumper the connection. The hard part, is figuring a way out physically,
of doing the jumpering. On some main power connectors, you can actually
touch the metal contacts, from the area where the wire enters the nylon
shell. Be careful that you are only making contact with PS_ON# and
COM, when doing your jumpering. (Basically, you don't want to short
anything else, because the short could get hot and burn you or burn
something else.) You would, of course, be doing this with a known good PSU
in place in the Emachine. And you would also have verified that in fact,
the original supply was an ATX. I don't know if eMachines ever dabbled
in non-ATX supplies or not.

Paul

 

[GlowingBlueMist]

But consider the evidence you've collected so far.

Since replacement PSUs are not doing anything, it would seem the eMachine
PSU has damaged its motherboard. Transferring a "known dangerous" PSU
into another machine is just asking for trouble, in the form of a damaged
second machine.

It is possible to "jump start" a PSU, by connecting PS_ON# to an adjacent
COM/GND pin. That bypasses the PS_ON# logic on the motherboard, and should
cause the PSU fan to spin. PS_ON# is open collector, which is why you can
safely jumper the connection. The hard part, is figuring a way out
physically,
of doing the jumpering. On some main power connectors, you can actually
touch the metal contacts, from the area where the wire enters the nylon
shell. Be careful that you are only making contact with PS_ON# and
COM, when doing your jumpering. (Basically, you don't want to short
anything else, because the short could get hot and burn you or burn
something else.) You would, of course, be doing this with a known good PSU
in place in the Emachine. And you would also have verified that in fact,
the original supply was an ATX. I don't know if eMachines ever dabbled
in non-ATX supplies or not.

Paul

I don't have one of those actual machines but this works for most chassis
that have a reset and power button on the front panel.

Try following the machines front panel power button (not reset button) wires
to the motherboard and make sure they are plugged in tight.

To test for an actual defective power reset switch unplug the power reset
cable from the motherboard and short the two pins together on the
motherboard and see if the system powers on. If this does not power on the
system (at least temporarily) you either have a defective motherboard, loose
cable from motherboard to the power supply, or a defective power supply.

 

[DaveW]

Do not try the questioned PSU in another machine. It might fry the
motherboard. In your machine it certainly sounds like the motherboard is
dead.

 

[paulmd]

Hey all,

Got an eMachine T2642 , Machine is not powering on at all. The power
supply reads 150W, 250W max. Ive tested 3 different power supplies, 2
375W max, and a 280W max. Still no dice. The leads seem to be fine as
well. Any idea what is going on here?? Is it alright to test this 150W/
250W max PS in another machine? or would it fry the board/machine if I
test it?? thanks guys!

Black and silver eMachine:
Dead motherboard AND power supply.

If yours matches the pattern of e-corpses i've seen.

 

[w_tom]

Others have properly warned about shotgunning - swapping parts.
Having done so, you still know nothing useful and may have
exponentially complicated the problem. But two minutes with a 3.5
digit multimeter (sold for about $20 in Lowes, Radio Shack, Wal-mart,
etc) would have quickly identified a suspect or a decisive action
plan. Currently, you are still speculating with no accomplishment.

First a reading on the purple wire from power supply to
motherboard. That DC voltage, even when computer is powered off (but
connected to AC) must exceed 4.87 volts DC. Next is green wire
voltage. That must be well above 2 volts AND then drop to less than
0.8 volts when power switch is pressed. At this point, a problem is
probably observed - post those numbers. If not, then move on.

Measure gray wire voltage before and when power supply is pressed.
It must rise to well above 2.4 volts within a second after power
switch is pressed.

And finally, voltages on any one of red, orange, and yellow wires.
Those voltages are observed as power switch is pressed; should remain
above 3.23, 4.87, and 11.7 volts. Which one(s) does not even attempt
to rise is useful information.

Your replies will only be as useful as information provided - and
that includes numbers; both good and bad numbers. Provide numbers to
receive useful actions AND to actually learn. As others noted, moving
a defective part from machine to machine may only create more
failures. Doubtful. But this is why 'informed' technicians first
collect facts before fixing anything.

 

[kony]

It is possible to "jump start" a PSU, by connecting PS_ON# to an adjacent
COM/GND pin. That bypasses the PS_ON# logic on the motherboard, and should
cause the PSU fan to spin. PS_ON# is open collector, which is why you can
safely jumper the connection. The hard part, is figuring a way out physically,
of doing the jumpering.

I typically put a multimeter in current measurement mode and
put needle tips on the probes to insert into the back of the
20/24 pin connector (while plugged into the board of
course).

 

[Rod Speed]

Others have properly warned about shotgunning - swapping parts.
Having done so, you still know nothing useful and may have
exponentially complicated the problem. But two minutes with a 3.5
digit multimeter (sold for about $20 in Lowes, Radio Shack, Wal-mart,
etc) would have quickly identified a suspect or a decisive action
plan. Currently, you are still speculating with no accomplishment.

First a reading on the purple wire from power supply to
motherboard. That DC voltage, even when computer is powered off (but
connected to AC) must exceed 4.87 volts DC. Next is green wire
voltage. That must be well above 2 volts AND then drop to less than
0.8 volts when power switch is pressed. At this point, a problem is
probably observed - post those numbers. If not, then move on.

Measure gray wire voltage before and when power supply is pressed.
It must rise to well above 2.4 volts within a second after power
switch is pressed.

And finally, voltages on any one of red, orange, and yellow wires.
Those voltages are observed as power switch is pressed; should remain
above 3.23, 4.87, and 11.7 volts.

He keeps plucking these stupid numbers out of his arse. They arent
anything like what the ATX specs say, and its the completely superfluous
proof that he hasnt got a clue about how a multimeter works.