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Do PSU's & Motherboards go bad together?

A P4 XP machine won't start. No beeping. No fans turn. There's a faint dull hum from the ATX P4 PSU when you plug it in. Something was rattling around in the PSU -- a transistor (those cylnder things) was disconnected. Plus there was dark brown goo stuff all over, but it looks like that might be a kind of adhesive to keep stuff together.

So I swapped in my good dell ATX P4 PSU into the non-starting PC.  Now the CPU fan in the non-starting PC came on, but nothing else that I can see.

NOTE -- no one opened this PC between the time it stopped working (loaded windows) and the time when I opened it to swap PSUs -- so I doubt jumpers are the issue.

I don't see any scorching / burn marks by the P1 or P4 cpu power connectors on the Mobo.

(1) Am I premature to declare "bad psu AND motherboard"?  

(2) How often do the PSU & Motherboard go bad (become damaged) together?

(3) Do PSU's often have amber or brown-colored drippy-looking gloops of dried "adhesive" strung around the interior to  hold together the transistors & what-not?

Thanks!
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dgrrr
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dgrrr
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djmounce553Commented:
1) Maybe a little premature. What kind of computer is this? Dell, HP, etc. Major computer builders like these often have proprietary power supplies/motherboards that work together. The 400W of power could come from many combinations. If you let us know what your exact model(if it's a dell, hp, etc) is, or what the motherboard model is (if it is a homebuilt).
2) Somewhat often. People who's power supplies die will sometimes just throw any power supply in there thinking it will work, when it can actually fry the computer.
3) Not sure, but I do know there is some adhesive in there.
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dgrrrAuthor Commented:
non-starting PC: emachines e2042
non-starting PC original (non-working) psu:  Bestec model# atx-250-12e  (output, 250w max)

my working replacement psu (that I put into the above emachine): Dell MOdel HP-P2507F3P  (output, 250w max) (+5v and 3.3v shall not exceed 150w)
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djmounce553Commented:
I am very glad that you didn't blow your motherboard or anything on it. The 150W worked to power only what it could which was not much. You need a 250W PSU. The one you need is here, same model and manufacturer as your previous one, and a pretty decent price for a proprietary PSU. http://www.circotech.com/gateway-emachine-bestec-atx-250-12e-ps-250w-replacement-power-supply-part-number-p-n-100744.html
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djmounce553Commented:
Sorry, the Dell one was 250W, but may not have been the correct voltage combination needed to run your system.
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nobusCommented:
>>   a transistor (those cylnder things) was disconnected    <<   probably a capacitor (blown ?) = 2 connections, transistor = 3
>>  Plus there was dark brown goo stuff all over   <<   confirms the above : blown electrolytic capacitor
So this PSU is bad. you'll have to replace it with one of the same wattage, at least, or higher. i would suggest a 300 W model
>>  (1) Am I premature to declare "bad psu AND motherboard"?  <<  if the power supply can handle the load, you may have a bad mobo and PSU
>>  (2) How often do the PSU & Motherboard go bad (become damaged) together?   <<  nobody can tell, it happens a lot, and depends on the kind of failure ; if a regulator on the mobo shorts out, it can ruin mobo and PSU together, or if the PSU sends a high voltage over the low voltage rails.
>>  3) Do PSU's often have amber or brown-colored drippy-looking gloops of dried "adhesive" strung around the interior to  hold together the transistors & what-not?   <<   it can be they fastened the components with some "heat-glue", that became brownish over the years (nicotine ?) passing thru ?

you can also testwith the minimum (recommended) : mobo + cpu + 1 ram stick, video card and psu ; any display ? if N, one of the connected is bad, try swapping ram, or video card, then cpu or mobo
if Y, add devices 1 by 1 till the bad one is found

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dgrrrAuthor Commented:
My main objective now is to choose between telling the user to get a new pc or to just get a new motherboard.  I hesitate to do the latter because when I put in a new atx p4 psu with matching wattage output (250w) nothing happened except the psu & cpu fans turned. (no lights on front, no beeping).  (NOTE - this was with minimum hardware). Just now I put in a second new (2nd replacement) psu (atx p4, but slightly lower output, 250w) and in addition to the psu fan and cpu fan turning, also, the power button flashed on and off green,, and the hard drive light flashed yellow.  Strangely when I connect the hard drive, the yellow hard drive light stays dark, adn the green power light flashes.

Lastly, with this 2nd replacment cpu, when I plug it in the first time, the above activity happens -- but if I unplug hte 3-pin power cable and plug it back into the psu, nothhing happens. I have to unplug ALL the psu cables inside the pc, and reconnecdt them, to get the above activity to  happen.
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dgrrrAuthor Commented:
PS -- I have never heard the computer beep when powering up. It does NOT beep even when the power light flashes.
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nobusCommented:
probably bad mobo, since you tested with 2 cpu's
250 W power supply maybe not enough, calculate what you need here :
http://extreme.outervision.com/psucalculator.jsp      
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