New PSU yet PC won't switch on

hopper · 03-16-2007, 09:05 PM

I'm fixing a couple-year-old Emachine T-series for someone.

After a power outage, it wouldn't turn on. Business as usual for an Emachine with a Bestec PSU. I've replaced dozens of them.

I plug it into my trusty Antec PSU tester and sure enough, it lights red. Install a brand new Antec 350W PSU. Still will not switch on or engage anything except the mobo LED.

So I thought the cheapo Emach switch may be at fault. Lo and behold I have an Emach carcass handy with a front panel and switch that I know works (the processor had fried and power was not the issue.) Switched panels and same result - nothing.

What do I look for next? Is the MOBO fried? If so, how do you make certain? I feel as if I should know the answer, but when it comes to hardware, I'm not quite an expert and I learn something new everyday. I hope you can help me learn something new today!

Thanks in advance

dai · 03-16-2007, 09:37 PM

what do the fans do when you try to start
reset the cmos
try with these only connected
cpu
ram
video
any beeps if you remove the ram or the video

**pharoah** · 03-16-2007, 10:00 PM

also i would double check all the psu connections make sure they are all tight.

edit: double check all connections period.

hopper · 03-16-2007, 10:08 PM

Thanks for the quick reply Dai,

When I first posted, no fans, no beeps. Not even the PSU fan, however when I had it plugged into the PSU tester, the PSU fan worked.

I reset CMOS. No fans, no beeps. No PSU fan. MOBO LED is on.

Plugged into PSU tester, PSU fan works.

Is that the answer to my question (bad MOBO?)

hopper · 03-16-2007, 10:22 PM

Quote:

Originally Posted by pharoah

also i would double check all the psu connections make sure they are all tight.

edit: double check all connections period.

Thanks pharoah,

I double-checked all PSU connections, and they are as they should be. The switch connections are exactly as they were when I removed the original front panel/switch.

When the PSU mobo connector is plugged into the tester, the PSU fan works. When plugged into the mobo, nothing.

It's dead, no?

dai · 03-16-2007, 11:01 PM

put the plug for the m/b from the old supply alongside the new one and check the same coloured wires go to each pin on both plugs
if they are the same i would think that you have lost the m/b

hopper · 03-16-2007, 11:10 PM

There are some different colored wires going to different pins. The old PSU is a Bestec 250W and the new one is an Antec 350W. I have an older 200W on hand that I could try, but I think you are right - blown mobo.

BTW, thanks for your help.

dai · 03-16-2007, 11:16 PM

the old supply may be propriortary not a standard atx,we don't see emachines here so it's just a thought not a knowledgable statement

hopper · 03-16-2007, 11:27 PM

I just double checked after reading your post - the old PSU is standard ATX-250. I've replaced dozens of these in Emach and Gateway and never had a problem replacing with Enlight or Antec PSUs.

I guess just for fun I'll try the 200W PSU from an older system. I just wish I could diagnose m/b failure easier with some degree of certainty.

dai · 03-16-2007, 11:33 PM

if you have another cpu you can put in to see if you can get any bios beeps

hopper · 03-16-2007, 11:46 PM

I don't think I have one (that I can spare)

I don't think the cpu is getting any juice anyway. The main socket on the m/b seems to be the weak link (as the PSU fan runs when plugged into a tester, thus completing the circuit. But not when plugged into m/b.) I'm no electrical genius however. Even if the processor was shot, wouldn't the other components still try to fire up?

I took the make and s/n off of the board and I will check their web resources tomorrow. All-in-all, the computer isn't worth the time we are spending on it.

I very much appreciate your help, Dai.

**Kalim** · 03-18-2007, 08:52 AM

Take everything off, even RAM, GPU and HDD. Keep HSF and CPU inside though and PSU connected aswell as LEDs and sound.
Fire it up, and it should give beeps and LEDs for missing RAM, HDD, GPU (if no onboard) and the fans should spin.

If that doesn't give anything at all, then I think your motherboard is dead. If it does, then you know its not the motherboard. Look around the CPU for the capacitors - they may smell, be bulging and leaking from the tops instead of sealed and tight flat. If you see that, then its the motherboard fried.

On the other hand, it could also be the CPU overheating. One of my P4's never turned on until I reapplied the thermal paste with a better HSF and before that nothing would happen, only the heatsink fan would spin if I connected it to my tester.

03-16-2007, 09:05 PM	#1 (permalink)
hopper Registered User Join Date: May 2005 Posts: 169 OS: XP / Ubuntu 6.10	New PSU yet PC won't switch on I'm fixing a couple-year-old Emachine T-series for someone. After a power outage, it wouldn't turn on. Business as usual for an Emachine with a Bestec PSU. I've replaced dozens of them. I plug it into my trusty Antec PSU tester and sure enough, it lights red. Install a brand new Antec 350W PSU. Still will not switch on or engage anything except the mobo LED. So I thought the cheapo Emach switch may be at fault. Lo and behold I have an Emach carcass handy with a front panel and switch that I know works (the processor had fried and power was not the issue.) Switched panels and same result - nothing. What do I look for next? Is the MOBO fried? If so, how do you make certain? I feel as if I should know the answer, but when it comes to hardware, I'm not quite an expert and I learn something new everyday. I hope you can help me learn something new today! Thanks in advance

03-16-2007, 09:37 PM	#2 (permalink)
dai Manager, Hardware Forums Join Date: Jul 2004 Location: west australia Posts: 41,845 OS: vista 32x ultimate retail	Re: New PSU yet PC won't switch on what do the fans do when you try to start reset the cmos try with these only connected cpu ram video any beeps if you remove the ram or the video __________________

03-16-2007, 10:00 PM	#3 (permalink)
pharoah Super Gaming Mod Join Date: Aug 2006 Posts: 4,778 OS: vista business edition My System	Re: New PSU yet PC won't switch on also i would double check all the psu connections make sure they are all tight. edit: double check all connections period. __________________ Follow These Steps First Power Supply Selection Posting System Specs Oblivion Tweak Guide Video Drivers& Information TSF folding at home team 85015 Last edited by pharoah : 03-16-2007 at 10:01 PM.

03-16-2007, 10:08 PM	#4 (permalink)
hopper Registered User Join Date: May 2005 Posts: 169 OS: XP / Ubuntu 6.10	Re: New PSU yet PC won't switch on Thanks for the quick reply Dai, When I first posted, no fans, no beeps. Not even the PSU fan, however when I had it plugged into the PSU tester, the PSU fan worked. I reset CMOS. No fans, no beeps. No PSU fan. MOBO LED is on. Plugged into PSU tester, PSU fan works. Is that the answer to my question (bad MOBO?)

03-16-2007, 11:01 PM	#6 (permalink)
dai Manager, Hardware Forums Join Date: Jul 2004 Location: west australia Posts: 41,845 OS: vista 32x ultimate retail	Re: New PSU yet PC won't switch on put the plug for the m/b from the old supply alongside the new one and check the same coloured wires go to each pin on both plugs if they are the same i would think that you have lost the m/b __________________

03-16-2007, 11:10 PM	#7 (permalink)
hopper Registered User Join Date: May 2005 Posts: 169 OS: XP / Ubuntu 6.10	Re: New PSU yet PC won't switch on There are some different colored wires going to different pins. The old PSU is a Bestec 250W and the new one is an Antec 350W. I have an older 200W on hand that I could try, but I think you are right - blown mobo. BTW, thanks for your help.

03-16-2007, 11:16 PM	#8 (permalink)
dai Manager, Hardware Forums Join Date: Jul 2004 Location: west australia Posts: 41,845 OS: vista 32x ultimate retail	Re: New PSU yet PC won't switch on the old supply may be propriortary not a standard atx,we don't see emachines here so it's just a thought not a knowledgable statement __________________

03-16-2007, 11:27 PM	#9 (permalink)
hopper Registered User Join Date: May 2005 Posts: 169 OS: XP / Ubuntu 6.10	Re: New PSU yet PC won't switch on I just double checked after reading your post - the old PSU is standard ATX-250. I've replaced dozens of these in Emach and Gateway and never had a problem replacing with Enlight or Antec PSUs. I guess just for fun I'll try the 200W PSU from an older system. I just wish I could diagnose m/b failure easier with some degree of certainty. Last edited by hopper : 03-16-2007 at 11:29 PM.

03-16-2007, 11:33 PM	#10 (permalink)
dai Manager, Hardware Forums Join Date: Jul 2004 Location: west australia Posts: 41,845 OS: vista 32x ultimate retail	Re: New PSU yet PC won't switch on if you have another cpu you can put in to see if you can get any bios beeps __________________

03-16-2007, 11:46 PM	#11 (permalink)
hopper Registered User Join Date: May 2005 Posts: 169 OS: XP / Ubuntu 6.10	Re: New PSU yet PC won't switch on I don't think I have one (that I can spare) I don't think the cpu is getting any juice anyway. The main socket on the m/b seems to be the weak link (as the PSU fan runs when plugged into a tester, thus completing the circuit. But not when plugged into m/b.) I'm no electrical genius however. Even if the processor was shot, wouldn't the other components still try to fire up? I took the make and s/n off of the board and I will check their web resources tomorrow. All-in-all, the computer isn't worth the time we are spending on it. I very much appreciate your help, Dai.

03-18-2007, 08:52 AM	#12 (permalink)
Kalim Roaming To Help Join Date: Nov 2006 Posts: 5,609 OS: Many	Re: New PSU yet PC won't switch on Take everything off, even RAM, GPU and HDD. Keep HSF and CPU inside though and PSU connected aswell as LEDs and sound. Fire it up, and it should give beeps and LEDs for missing RAM, HDD, GPU (if no onboard) and the fans should spin. If that doesn't give anything at all, then I think your motherboard is dead. If it does, then you know its not the motherboard. Look around the CPU for the capacitors - they may smell, be bulging and leaking from the tops instead of sealed and tight flat. If you see that, then its the motherboard fried. On the other hand, it could also be the CPU overheating. One of my P4's never turned on until I reapplied the thermal paste with a better HSF and before that nothing would happen, only the heatsink fan would spin if I connected it to my tester.