PC molex power

[ElectricN00b]

Hello experts,

I have a question about an external molex power supply. It's a 34W rated power supply commonly found on ebay. The pinout is:

12v @ 2a | not connected | ground | 5v @ 2a

Can anyone please give me the possible reason for the non-connection of pin 2? Normally that pin is a ground. This is a problem because some disk drives will only work if both grounds are connected. I can get them to work by connecting the two ground pins together. But, I am concerned by unexpected moments when things could start smoking.

The cable between the the power brick and the molex connector is: "AWM E138922 STYLE 2464 80C (celcius) 300V VM-1SC CSA LL81295 | A/B 80C 300V FT1". Is the single ground wire in this cable capable of handling the load if both the 12v and 5v lines are at maximum output? Since the power supply is a cheapo unit, there may be plus or minus deviations on both the voltage and amperage. What is the likely maximum watts the single ground wire can handle?

Thanks.

 

[James]

If the power supply is designed to provide both 12v and 5v to that plug with a common ground connection, the ground wire should have been specified to carry the full maximum currents of both positive wires combined (4A)

If you have concerns about not having enough pins connected to run your devices, why not buy a PSU that has all pins connected.?

Also note, some items on eBay are of questionable quality and may not be tested to the required standards for sale or use in the uk.

If you are concerned, why not support your local computer shop, instead of taking a chance on something unknown?

 

[ElectricN00b]

Mine was very much a technical question relating to an item I already have. As for the philosophy of it, well, local computer shops don't do this kind of power supply. Even if they do, I cannot buy from them because I already have something. If the local computer shops need support, perhaps the government should step in? All they have to do is switch on the printing machine, and wealth will spew out of it.

I have a kettle lead that connects from the mains to the power brick. That lead will be able to handle the full load. The power brick then has an output lead as I have described. My question is to do with if that output lead can handle the load. I know nothing about electrics and unable to decipher the markings on the lead. Hence the question.

Since all marking on the lead are in english, it must be the product a western company. In a way I am already supporting a non-chinese company by having this chinese power supply, which likely to contain many components from other non-chinese companies.

 

[ElectricN00b]

Found the likely reason why one of the ground pins was not connected. It was because there was expectation that the two ground pins would be bridged on the disk drive end. However, not all disk drives follow this convention.

With the output cable rated for 300v and made by canadians, at a guess, I think the cable can handle the load.

 

[DPG]

Found the likely reason why one of the ground pins was not connected. It was because there was expectation that the two ground pins would be bridged on the disk drive end. However, not all disk drives follow this convention.

With the output cable rated for 300v and made by canadians, at a guess, I think the cable can handle the load.

The voltage rating of the cable is purely down to its insulation, nothing to do with how much current it can handle.

 

[ElectricN00b]

Thanks, I know nothing about electrics. So, I had to shoot in the dark

As a test, I will use a high draw device and keep a hand on that cable to make sure it's not heating up.

My concern originally arose out of the fear that the PSU maker not connecting one of the grounds was because the cable was not capable of supporting a 34w return path. This fear now seems misplaced because there is a plausible alternate reason why the pin was not connected.

I am puzzled though. Are the markings on cable not useful for identifying the characteristics of the cable? From my searching, I know CSA is a canadian standard. 80C is the do not exceed temperature. FT1 is the fire performance. Shouldn't there be something to indicate the current limits?

With a magnifying glass, I can see better the markings. It is:

"AWM E138922 STYLE 2464 80C 300V VM-1SC CSA LL81295 II A/B 80C 300V FT1"

 

[DPG]

You would probably have to look the candle up on the internet to find out the current handling capacity. You won't find it on a lot of cables because it depends on the environment the cable is run in.

 

[ElectricN00b]

I did search for those magic numbers, but didn't find anything useful. The internet is more interested to sell me the marking tools for cables.

I'll just use my hand on cable method Thanks for your comment.