New power supply not working

[mctigue]

My eMachine T2240 power supply has died so I purchased a new power supply from an on-line vendor. I purchased a Maxpower 400 watt power supply to replace the Bestec 250 watt power supply that died. However, now the CPU fan comes on but nothing else starts. I do not even get a BIOS screen. Is it possible that this power supply is too much for the system to handle? Do I need to replace with a similar wattage power supply? Or are there jumpers on the motherboard that can be set for this larger wattage power supply? By the way, the vendor's website claimed that the power supply works with the T2240.Your advice is greatly appreciated.

[saphalline]

If your old PSU died and the new one isn't breathing life into your system, then it's likely that your old PSU fried something when it died. At this point, you'll have to do a total systems diagnostic to find out what still works and what doesn't.

[Fred_Flintstone]

Is it possible that this power supply is too much for the system to handle? Do I need to replace with a similar wattage power supply?

I am not an electronics expert by any means.. :rolleyes:

But, as I see (and understand) it..the only question that matters is...

Is my system too much for my Power supply!!
It doesn't work the other way round...if your system needs say.. 300watts and you have a 200 watt PSU.. problem!!..PSU overheats because it can't "keep up".. :eek:

But if your system needs say..300 watts and you have a 400 watt PSU.. it just sits there and works at 75% capacity and say's "bring it on baby is that the best you can do!!"

The Power supply doesn't Pump power into your system..
The system draws power from the PSU.. as much as it needs and no more.. :p

I am sure that if I am incorrect in my assumtions.. :p

Some techie will come along and shoot me down.. :confused: :confused:

[Fred_Flintstone]

As an "aside" to above..

A few months ago.. my E-machines pc died... :mad:
The PSU had fried.. and when I replaced it.. it still wouldn't boot!!

Turned out, it (PSU) had fried/taken the mobo down with it.. changed both (PSU & MOBO) and all was well.. :rolleyes:
Good luck.. ;)

[saphalline]

I am sure that if I am incorrect in my assumtions.. Some techie will come along and shoot me down..You are mostly correct.

There is indeed a point at which more is no longer better. A 600W PSU for a system that only draws 100W is another problem altogether. In this case, the PSU's power usage doesn't reach a "critical mass" of power comsumption that is needed to keep the PSU's AC/DC converter circuits going. So too much power is also bad, but in a different way.

There is also the belief that a 400W PSU can operate at 400W at all times. This is most definitely NOT true! PSU's are the one component that cannot operate at 100% with any reliability. They are designed to operate at their peak wattage only during power-up (when the system is booting) and are thereafter supposed to operate at a constant power draw of 40-80% or so. If you use one of those wattage calculators to add up the power draw of all your components, you should always add a third to get the peak wattage rating of your system's ideal PSU.

[jlreich]

There is indeed a point at which more is no longer better. A 600W PSU for a system that only draws 100W is another problem altogether. In this case, the PSU's power usage doesn't reach a "critical mass" of power comsumption that is needed to keep the PSU's AC/DC converter circuits going. So too much power is also bad, but in a different way.
So what would be a good rule of thumb with this? Maybe no more than 200% of the estimated actual draw of your system? Or maybe even 300%??

Of course it would be a waste to buy a 600W PSU for a system that only needs 300W and has some to spare... Just looking for what really is too much.

EDIT -
and are thereafter supposed to operate at a constant power draw of 40-80% or so.
Well looking at that I guess it would mean to make sure your actual draw should at least be equal to 40% of the rated wattage??

[mctigue]

It may take a new motherboard to fix the problem. Any advice on where to look on-line for a good replacement for this model (emachine T2240). I am glad to hear that the PSU is not too much for the system. This advice helps with the troubleshooting process. Thanks to everyone for the advice.

[Fred_Flintstone]

You are mostly correct

See!!.. told you so!!.. :D :D :D

Only joking Saph...

But seriously.. the point I was making is that some people think that if they get a BIG PSU it is going to blitz their system with the rated power..eg. 500watt means it's going to pump that amount of power in and fry a system that only requires 350 or 400 watt. :rolleyes:

[saphalline]

You don't necessarily want to shoot for the low end, but giving yourself plenty of room is good for upgrading. Ie, you don't want to stick a 450W PSU into a high end gaming system, because then you'll have to upgrade the PSU if you add so much as another hard drive. :rolleyes: And don't use the wattage value of your CPU/vid card at idle - use the full load wattage value.

Check EBay for your mobo. Or eMachines, which is Gateway now. Those are the only two places that would have an identical mobo for your system.

That's a good point. I forget that people think that sometimes. It's really quite odd all the rumours and misconceptions flying around out there when it comes to PSU's.

[kpmwrestler]

I am not an electronics expert by any means.. :rolleyes:

But, as I see (and understand) it..the only question that matters is...

Is my system too much for my Power supply!!
It doesn't work the other way round...if your system needs say.. 300watts and you have a 200 watt PSU.. problem!!..PSU overheats because it can't "keep up".. :eek:

But if your system needs say..300 watts and you have a 400 watt PSU.. it just sits there and works at 75% capacity and say's "bring it on baby is that the best you can do!!"



But I've looked at the chart on an emachines power supply before and found that the 400 watt psu lets more power pass through than a 200 watt. I don't
remember the chart, but something like if the 200 watt let out so many amps, the 400 watt let out two more amps than the 200.

[Fruss Tray Ted]

found that the 400 watt psu lets more power pass through than a 200 watt

Not exactly. A power supply provides a 'potential' power to a device. In this case a pc. But a PSU has more than one 'rail' too. A 200 watt PSU may not have enough 12 volt power in a survey and therefore fail or be inferior to the 400 watt supply in the comparison. But it may have ample 5 volt power or 3.3 etc.

Wrestler,
It is not a matter of how much power the PSU 'lets out', it's how much the arrangement (mobo, RAM, GPU, soundcard,,,) draws. If the PSU is insufficient to the arrangement, things won't work due to lack of power, but if a power supply is more than enough, no harm will come to those peripherals because the voltages themselves are not exceeded. One or 2 amperes in some survey you read about seems moot imo

[mjc]

Wrestler,
It is not a matter of how much power the PSU 'lets out', it's how much the arrangement (mobo, RAM, GPU, soundcard,,,) draws. If the PSU is insufficient to the arrangement, things won't work due to lack of power, but if a power supply is more than enough, no harm will come to those peripherals because the voltages themselves are not exceeded. One or 2 amperes in some survey you read about seems moot imo

Plus the draw is not constant. When a drive is not being actively used, it draws little or no power, but when you need it to do something, it hits the 12V rail.

Fans will always be using some, but use more when first being turned on and so on.

So at idle your machine may only be using 150W, but when you hit the power button, it may take over 400W to get it going.