Power supply guilty?

[jodleren]

Hi all

I dont know if this is the right place?

I am trying to put togther a PC for my GFs parent.

I have it all, but there is a problem with the power - I have 2 main
boards, they act the same way. Though - now 4 power supplies:

1 - main board starts up, resets a few times, or might work, will shut
down before anything really happens
2 - nothing happens (I wonder why I kept this power supply)
3 - CPU fan starts for 1 second then it stops
4 - old, big, noisy, but works

Can it be, that this is a power supply problem? I used one mainboard
and stuff on my table, then it worked. Next, it doesnt. To me it looks
like the power supply shuts off - meaning that I need a new power
supply and I am running. Does the power supply check used power then
fails?
I use the "current" one, where the main board turns on the power
supply.
The current test set gives 5V nicely, I have checked them all.

I have some 5 computers in our living room, my GF likes to get rid of
them

Sonnich

 

[jinxy]

Hi all

I dont know if this is the right place?

I am trying to put togther a PC for my GFs parent.

I have it all, but there is a problem with the power - I have 2 main
boards, they act the same way. Though - now 4 power supplies:

1 - main board starts up, resets a few times, or might work, will shut
down before anything really happens
2 - nothing happens (I wonder why I kept this power supply)
3 - CPU fan starts for 1 second then it stops
4 - old, big, noisy, but works

Can it be, that this is a power supply problem? I used one mainboard
and stuff on my table, then it worked. Next, it doesnt. To me it looks
like the power supply shuts off - meaning that I need a new power
supply and I am running. Does the power supply check used power then
fails?
I use the "current" one, where the main board turns on the power
supply.
The current test set gives 5V nicely, I have checked them all.

I have some 5 computers in our living room, my GF likes to get rid of
them

Sonnich

If you have 5 pc's , then why not try a power supply from one of
those?
-J

 

[larry moe 'n curly]

I am trying to put togther a PC for my GFs parent.

I have it all, but there is a problem with the power - I have 2 main
boards, they act the same way. Though - now 4 power supplies:

1 - main board starts up, resets a few times, or might work, will shut
down before anything really happens
2 - nothing happens (I wonder why I kept this power supply)
3 - CPU fan starts for 1 second then it stops
4 - old, big, noisy, but works

Can it be, that this is a power supply problem? I used one mainboard
and stuff on my table, then it worked. Next, it doesnt. To me it looks
like the power supply shuts off - meaning that I need a new power
supply and I am running. Does the power supply check used power then
fails?
I use the "current" one, where the main board turns on the power supply.
The current test set gives 5V nicely, I have checked them all.

I have some 5 computers in our living room, my GF likes to get rid of them

Be careful about testing mainboards outside the computer because it's
easy to zap them with static electricity, especially on plastic-
covered tables. Place some anti-static material under the mainboard,
such as the sheet of foam wrap include with every new mainboard, or
pink anti-static bubble wrap. If none are available, a metallic
plastic bag turned inside-out will work (the outside is actually not
anti-static), and as a last resort, try several layers of non-shiney
brown paper or newsprint.

Have you tested the PSUs with the bent paperclip and a cheap digital
multimeter? Harbor Freight has a model for $3, with coupon that's
very accurate. Here's the procedure for testing:

http://www.overclock.net/faqs/96712-how-jump-start-power-supply-psu.html

There are also some YouTube videos about this.

What brands are those PSUs? PSUs vary more in quality than about any
other computer component, and a lot of them, even major brands, are
made with bad capacitors that can rot out, even in storage.

..

 

[jodleren]

If you have 5 pc's , then why not try a power supply from one of
those?
-J

I have 5 computer cases w/stuff but only 3 power supplies

 

[Paul]

I have 5 computer cases w/stuff but only 3 power supplies

In your description, you don't mention the make and model number
of motherboard. Are you putting together a system using really
old components ? Or, are all the components newly purchased from
the store, and you're attempting to assemble them ?

Really old motherboards, need -5V. (Well, they don't need it as such,
but they check for it anyway.) Look at the main power supply connector.
On modern power supplies, there is a pin that is missing. That pin
is where the -5V output used to be carried. Modern power
supplies no longer carry -5V. And that is a problem, if you
are using an older motherboard, mixed with a newer power supply.
For example, I need to change the power supply on my oldest computer,
and I will not be able to find a supply that still has -5V.

That doesn't account for your symptoms though.

1) main board starts up, resets a few times, or might work, will shut
down before anything really happens.

That could be a power supply issue, causing the motherboard to reset
because Power_Good doesn't remain valid. Connect the power supply to
a load box, and verify it can handle a decent loading. Or, purchase
a brand new power supply with exceptional rating, and test with that.

3) CPU fan starts for 1 second then it stops

Check that the CPU fan delivers an RPM signal. (You can do that,
by connecting the CPU fan to a working computer motherboard, then
using the hardware monitor and Speedfan, to check RPM readout.)

Check that the *heatsink* on the CPU is in physical contact
with the top of the CPU, and is cooling it. Your symptoms
suggest either a fan which lacks a working RPM pulse on the
third wire, or a CPU that is overheating because the heatsink
is not firmly clamped to the CPU.

If the CPU has a 1x4 (tiny connector, not Molex) and is from
a modern Intel CPU box, then you would be concerned about it
not fitting an older motherboard three pin fan connector. The
4 pin fan connector, can fit over the 3 pin fan connector. The
extra pin "sits in the air" and is not connected. That signal is
called PWM, and does not need to be connected for the test you're
trying to carry out. The three necessary pins (GND, +12V, RPM) will
be connected, when you plug a four pin fan into a three pin header.
The fourth signal, PWM, float to logic 1 and that causes the
fan to run at full speed. And that is why PWM does not need to be
connected - because it operates properly when it "floats in the air".
If you're getting a good and valid RPM readout, by testing the CPU
fan on another motherboard, then you know that isn't the problem.

I do *not* recommend, plugging fan cables into fan headers, while
the computer is running. Always shut the computer down, before making
changes to the fan connections. If you do that, there will be less
risk of damage to the computer. The "tab" on the fan connector and
motherboard should line up - that alignment tab prevents improper
insertion. Make sure you're not forcing the fan on backwards (rotated
the connector 180 degrees from correct position).

Paul

 

[Man-wai Chang]

I am trying to put togther a PC for my GFs parent.

I have it all, but there is a problem with the power - I have 2 main
boards, they act the same way. Though - now 4 power supplies:

You should list all hardware in the message!

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[Loren Pechtel]

Hi all

I dont know if this is the right place?

I am trying to put togther a PC for my GFs parent.

I have it all, but there is a problem with the power - I have 2 main
boards, they act the same way. Though - now 4 power supplies:

1 - main board starts up, resets a few times, or might work, will shut
down before anything really happens
2 - nothing happens (I wonder why I kept this power supply)
3 - CPU fan starts for 1 second then it stops
4 - old, big, noisy, but works

Can it be, that this is a power supply problem? I used one mainboard
and stuff on my table, then it worked. Next, it doesnt. To me it looks
like the power supply shuts off - meaning that I need a new power
supply and I am running. Does the power supply check used power then
fails?
I use the "current" one, where the main board turns on the power
supply.
The current test set gives 5V nicely, I have checked them all.

I have some 5 computers in our living room, my GF likes to get rid of
them

Sonnich

I'm going to guess there's a defective component somewhere that's
drawing off too much power.