AC to Molex adapter problem.

[mxnerd]

I have an AC to Molex power adapter from an AC to Molex/IDE/SATA package.

The adapter powers up IDE/SATA drive without problem, which is rated 12V/2A & 5V/2A.

When I tried to use the same adapter to power any computer fan (all 12V) with molex connector, size from 60mm to 120mm, none of them can be powered up, and all of them are rated between 0.1 to 0.8A.

Why is that? Can anyone explain? Thanks.

 

[ComputerWizKid]

I also have one of those adapters and the problem with most of them is the missing ground pin on the 12V side as the fan only has two wires and it uses the ground wire on the 12Volt side. You either have to use the other ground or rewire your fan to do so

 

[mxnerd]

I see. Thanks. I searched the net and found that the there should be 2 black wires in the middle. When I look at the Molex connector on my adapter, it looks like it does miss one ground wire, I don't know it's missing just the end or it's missing the whole wire.

Since the Molex connector of the adapter is molded, maybe I should cut the molded Molex connector and wire my own (I'm not familiar with AC)? I do have a lot of unused Molex connectors.

 

[ComputerWizKid]

In the connector cord there is probably only Three wires. The adapter is only rated for 2A @ 5/12Volts dc so there is little chance of the ground wire getting overloaded
The wires would be +5 Volts DC +12Volts DC and a common ground (in normal PC Power supplies there is two ground wires to help evenly distribute the load but electrically it goes to the same place in the PSU so with a load as light as a fan you will not need an extra ground)

I never cut the end off of one of those supplies so I don't know what color the wires on inside so you will need a multimeter to check the voltages
but in general PC wiring the yellow=+12VDC Black=Ground/Common Red=5VDC
If you need anymore help feel free to post

 

[mxnerd]

Thanks. I cut the Molex connector and 3 wires were revealed. Red, yellow and white.

The stranded wires are so thin I'm really afraid that I'll break it. I guess I had to solder it.

The white wire should be the ground wire. I'll test the wires using my multimeter which I have to locate since I haven't used it for a long time.

Thanks again.

 

[Modelworks]

If the adapter is meant for 5V and 12V then you may have an issue where the supply needs a load on both voltages for it to work. Try plugging a hard drive into the adapter then adding the fan. If that works then you need a resistor between the 5V and ground to make the adapter work with just the 12V

 

[ComputerWizKid]

To ModelWorks:
here is a link of the adapter it is not a normal PC Power supply it's a power brick like a laptop uses but is for one of those hard drive tester tools. it is indeed missing the ground for the +12V side of the plug (Which is the ground wire the fan uses so the fan is only 1/2 connected)
Also does a PSU brick need a minimal load like the standard PC PSU does?

 

[mxnerd]

I tested the wires with found multimeter. And you know what? Yellow to white is 5.2V and Red to white is 7.2V ! Completely different from what I thought!

So I guess I have to split the yellow wire into two part, the 1st part purely for 5V (5.2V) and 2nd part should bind with red wire to make a 12V (12.4V)?

 

[poofyhairguy]

I found an adaptor the other day that does exactly what you want:

http://www.amazon.com/Zalman-ZM-MC1-.../dp/B000FAKUE6

 

[mxnerd]

I found an adaptor the other day that does exactly what you want:

http://www.amazon.com/Zalman-ZM-MC1-.../dp/B000FAKUE6

That requires 4-wire Molex. What I have is 3-wire Molex and non-standard voltages.

 

[mxnerd]

I tested further this morning and found that I read it wrong yesterday.

It's +7.2V and -5.2V ( I did not realized there was a - in the reading ) , not +5.2V !

What should I do now?

 

[mxnerd]

I got it all wrong again. After further thinking, I figured that Yellow is the ground, not White.

So Red to Yellow is 12V, and White to Yellow is 5V!

Sometimes You really can't use conventional wisdom when dealing with some cheap China product. Sigh.

 

[mxnerd]

Used wire connectors and connect the adapter wires and Molex connector, wrapped with wire tape. Finally make the adapter work with fans and hard drives. Really happy now.