Nube with a couple of easy questions.

fitZ

New Member
Hi guys, nube here with a few simple questions.

I just finished installing everything from an older computer to a newly modded case and after connecting everything I tried to boot it with no monitor, keyboard or mouse, just to see if the power supply kicked on. I didn't think this would hurt anything but it wouldn't fire up. This is my secondary computer and is an old Gigabyte P4 mobo that I recently upgraded and maxed the CPU/RAM. It worked perfectly before I installed it in the new modded case

Ok, after disconnecting all the drives etc, I pulled the 20 pin mobo connector and shorted pin 14 to ground and the PSU fired up normally. I checked the voltages on all the pins and everything seems to be fine. I reconnected the PSU to everything and started checking the power switch wiring.
Here's the deal though. This computer is one of two that reside in a soundproof enclosure in my recording studio console. Because of that, I extended all the wiring for the power switch, restart switch, power led and HD led to a panel on the console via a 9 pin Dsub out from a PCI cover on the back. This extended circuit has worked for four years. I've double checked this wiring, the Dsub, and then pulled the connectors at the motherboard and tried shorting across the two pins on the mobo that go to the power switch. Still won't power up the PSU. So, my first question is...does all the external peripherals have to be connected for the PSU to power up? It seems they shouldn't but that's why I'm asking. Perhaps I've accidentally damaged the mobo during the install, but I'm really careful with this stuff. Is there any other test that you can think of? Oh, one other thing that might tell you something.

When I plugged the power cable into the PSU, I noticed the power LED came on immediately, even though I hadn't tried to power it up. I decided to turn the PSU switch off, and the led went out. I switched it again to on, and the led lit up again, without trying to boot. Weird. I checked the wiring for the led again, and nothing has changed. Everything is exactly as it was before. I double checked the mobo manual for the power LED pinouts and everything is correct. Sooooooo...any ideas?

Ok, second thing. I also came across something that is so simple, yet it has me perplexed. First off, I'm certainly no tech, but I have built and modded a few computers, so I'm not a complete computer nube. So, like my main computer mod, as I modded this case, I added a few LED's via extra molex connectors. Which worked just fine. I made up three parallel 12v circuits, from one molex, using the RED/BLACK wires as the connection point. I added appropiate resistors and voila...led lights. I used the RED/BLACK as over the years, when changing Case Fans, which are 12v, and are ALWAYS connected to the RED/BLACK wires in Molex connectors, all this time, because the fans and LED's always worked just fine, I ASSUMED these red and black wires were a 12v circuit, and the YELLOW/BLACK were some other voltage. Dumb me. I never checked them with a voltage meter.

Yesterday, while doing some research on "mini" Molex connectors(like the ones connecting old AGP graphics cards) I came across a diagram showing the voltages for the YELLOW/BLACK and RED/BLACK circuits from the PSU. WTF??? It showed the YELLOW/BLACK was the 12v..and the RED/BLACK was 5v. I was stunned. What the heck is going on????? Why do all the case fans I've ever bought, connect to a small mini molex, that in turn, is connected to the RED/BLACK wires at a standard Molex connector??? What am I missing here? I just measured the voltage of these wires and sure enough ...YELLOW/BLACK =12v, RED/BLACK=5v. So why are case fans connected to the RED/BLACK wires? I assumed all along these fans were 12v....no? Could someone please clue me in. I'm really perplexed about this seemingly simple conundrum.

Thanks.
 
I'll answer the easy question with this.

No, you do not need to attach monitor, keyboard, mouse in order to boot up a computer, it will still turn on. I'm guessing you have some sort of short somewhere. You say you transferred stuff to a new case.... Did you install the brass standoffs before attaching motherboard to case?
 
No, you do not need to attach monitor, keyboard, mouse in order to boot up a computer, it will still turn on
Hi. Ok, that's what I thought. In fact, I've done it many times. I just thought there might be some kind of glitch doing it.

Did you install the brass standoffs before attaching motherboard to case?
What's this tell you.:D

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Just kidding. Yes, I did. Even used fiber washers. And thanks for the first answer.
fitZ
 
bump?

Well, I came across another question. Anyone know where to find the same kind of power connectors found on old AGP graphics cards...only for cables. I have a whole bunch of cables that I need small 4 pin connectors for. I have the female part, found on PSU wiring cables. I just need the opposite part. I've searched but to no avail.
Still waiting for an explanation on the 12v/5v thing too.
Thanks.
 
When you say Molex and Mini Molex, I guess your talking about these. The name Molex is a companies name that makes connectors, really any connector can be called a Molex if Molex makes them. Anyway are these the ones your talking about?
800px-Molex_male_connector.jpg

and
4pin-floppy.jpg


If so the 5V is Red and the 12V is Yellow.
 
Hi. Thanks for the reply. Ok, like I said, the one I'm looking for is a "Berg MINI molex...exactly like the one in your BOTTOM picture. Only I'm looking for the MALE with pins, that can be soldered to wires. These are found on Floppy drives, and graphics cards, but they have the connector soldered to the circuit board.

As to the voltage, yes I already understand that Yellow is 12v, and red is 5v. However, also like I said, the thing I do NOT understand is, why case fans come with a connector that plugs into a small connector that is usually an extension off of a standard molex connector, but the wires are connected to the RED and BLACK...which means it connects to 5volts...when everyone knows Fans are 12v:confused::confused::confused: So what is going on here???? I double checked two computers, and all the case fans etc are connected to the RED and BLACK PSU wires through the molex connectors.

Can someone explain this?? I'm really perplexed.

As to the mobo problem...haven't got a clue. It appears to be fried, but I can't find any "burns" or cracks or anything. Well, I guess it's just one of those things. Dang. Time for a new motherboard. I was almost ready to upgrade this computer anyway, so I guess it's time.

Thanks
 
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