Topic: 4 pin molex to 6 pin pci-e connector. Word of warning - page 3. (Read 111408 times)

If you feel comfortable with a soldering iron in your hand, rock on.
Twist the copper wires together and don't skimp on the solder, give them as much as they will soak.
Just don't forget to put the shrink-wrap insulation in place before soldering the wires together

PCIE 6-pin/8-pin plugs and contacts can be easily ordered online, you can make any kind of connector you need without that messy wire soldering.

Also, that 2*molex -> PCIE 6-pin you mentioned before looks up to the job.

EDIT::
Since you mention this is an old PSU, have you tested whether it will run with no load at 5V / 3.3V rails?
More importantly, won't it jump out of spec under the cross-load condition?
You might need to load the 5V rail with a power resistor.

Do you happen to have a multimeter lying around? Power up the card, and measure voltage on some other 12V cable connected to the same rail.
A double-rail design will likely have rail1 connected to the ATX12V connector (and perhaps the ATX 24-pin connector) and rail2 to all sata/peripheral connectors.
When in doubt and the user manual is inaccessible, open up the PSU and verify rail setup visually.
Measure again with the card having ran fully overclocked for a couple of hours. Better safe than sorry.

Would it be safe to solder these things yourself?

I have an old spare PSU thats rated for 450W (350W on 12V, one 14A and one 15A rail) which should be plenty to power 1 5850 until my new PSU arrives.

Thing is, its old and has zero PCI-E connectors and only 2 molex connectors. And like a dozen SATA connectors.

If I were to cut my now defunct molex to PCIe adapter (keep the PCIe part), and cut some wires from the PSU (sata or maybe even from the motherboard or 4/8 pin CPU connector?)  and manually solder them.. would that be a good idea or drop dead stupid?

What a god-awful hack crimping two 20 AWG wires together at the molex⁽¹⁾ contact, where all the current will flow...
That sure is a fire waiting to happen.

And no matter what, don't ever use a sata-> molex adapter for powering anything more than a hard drive!
The SATA connector is rated much lower than that molex connector, at 4.5 amps max under ideal circumstances.



Notes:
(1) Actually, the four contact "Molex" connector should be called the 4 pin peripheral connector but everyone just calls it a molex.

Just to confirm my OP. Yesterday another 5850 arrived, and while I was waiting for a new PSU, I tested it with what I had, using one 2 molex -> PCIe cable and one 1 molex > PCIe cable.

Card ran fine for a few hours, then I started overclocking. After 2 hours or so at 850 MHz, something started to smell burned. Sure enough, the single molex to PCIe cable was hot to the touch and where the 2 yellow cables connect inside the molex connector a brown stain was forming. It was melting.
The 2 molex to PCie cable, which uses only 1 yellow wire per connector, was fine.

Morale: use these things at your own risk.

It as burnt ALL of the shroud around end pin of the 20 pin connector. through one side of the connector on the MoBo nearly and a pin on the 4 pin connector on the PSU. It is a AK1200, not HCP1200 i picked up for 145 from 210 or something. Basically HACP replaces the AK.

It's dangerous, wish i could get it independently tested but that could be time consuming, costly and may not give me an answer in the end. I replaced the mobo with a MSI one and not a problem. Although thatAK will not be plugged in another mobo with that damage again

An example of 'bad sag' - I had a 450W diablotek (avoid!) PSU who's 12V rail sagged to 10.4V powering just a 35W celeron and a single 5830.  I turned it off immediately and thanked the gods it hadn't fried anything up yet.

Anything >11.5V I'd consider perfectly acceptable on a 12V rail, so yours isn't bad.  I was getting 11.8V or so on a nice Corsair 750W running 3 cards.



Nah the 'same kind of thing' i was referring to was the voltage sag.  Basically, like a chain, the weakest point in a circuit is going to burn out when over-current.  In m3sh3aD's unfortunate case it was his ATX header, was thinking in yours it was the molex plug.

Hmmm. same kind of what thing? Also not sure what a "bad sag" is, but now that you mention it, the burnt molex connector was on my mining rig and that was with an old rather crappy 450W PSU that only powers a single 5850 and a hdd. I have measured voltages (just with a multimeter) and they seem stable, but 12V is only ~11.6-11.7v under load.

If you meant to ask if there could be  a relationship with my desktop where the 4 pin fell out; no, none. Different machine, and this one has a nearly new Zalman 650W thats working perfectly.

Appears the majority of the damage happened on the edge of the 20pin connector.  It also looks like the plastic shroud around the pin got left behind in the motherboard header, though it's hard to tell from the blurrycam.  It doesn't seem like coming-loose caused it.

I tried to find some info on those Akasa PSUs, they seem to be good little buggers, and definitely have short-circuit protection, so that's also unlikely.

With only 4 cards, and only 3 possibly pulling from the ATX header directly, the only thing that makes sense to me is a serious voltage sag.  If the 12V rail somehow dipped way under spec, the current needed to compensate would have increased greatly, which could definitely lead to this kind of failure while possibly missing the short-circuit protection.

That kind of thing doesn't normally happen without really excessive draw though, so this is a bit of a mystery.

[edit] This thread got way off track   P4man, the same kind of thing could blow the pins in a 4pin molex connector for the same reason, have you measured the voltage on your 12V rails to see if you've got bad sag?

Any decent PSU should have short circuit protection, so Im not sure thats it.

Just a wild guess, Ive had a motherboard where that 4 pin ATX connector doesnt lock in to place. The "lid" is only in the middle and locks the 20 pins, but not the extra 4 pin if you PSU has a 20+4 pin connector like that. If its not securely put in place, it could loosen itself and bad things might happen.

Actually just a few days ago I pretty much had that exact issue only with a 4 pin cpu connector loosening itself (PSU has 2x4 pin for CPU, motherboard only 1x4 pin, and both PSU leads fit, and work, but only one "clicks". I had used the wrong one). Out of the blue my computer shut down and would no longer boot. Turns out that connector came came lose. Luckily nothing was damaged, but I imagine had it been pulling 20+A and release slowly, it could have turned in to a lightshow.

just sapphire 5850 xtremes

Crazy issue

Well 225W would definitely cause that but no card pulls the max from PCIe slot.  While the slot *CAN* support 75W even 5970s pulls ~30W at peak load (remember that is for 2x GPU) from the PCIe slot.  The rest comes from the power connectors.

Which cards were they, just curious. 

The reality is most MB manufacturers aren't going to design their board to handle 7x75W just because it has 7 PCIe slots.  Maybe they should but they don't because outside of us insane miner's nobody loads a MB like that.  MB companies cut corners figuring x watts is enough.

Please tell me you're not using that blown 24pin ATX connector to power another board?

The damage on the board looks like a short, considering the plastic around the pin of your PSU's connector seems to have been left behind.  It would appear that something connected your 12V rail to ground at low resistance.. stray wire around your PCI-e ports or something similar.

If you're still using that PSU with the busted connector.. stop.  That's just asking to start a fire and/or destroy another board.

[edit] I suppose if you're using it to only power the 4 cards directly, and not using that 24pin connector it's probably ok, as long as no +V got got spot-welded to a G when it blew

4 cards, 1 card on a powered extender. so 3x75=225 through PCIE, surely not enough to cause that. 5850's.

It looks like the most damage is on pin #10 which is 12V connector.  Likely supplying power to PCIe slots.
What were the 4 cards?
Powered extenders?

Learn something new everyday. Cheers. Never had to look into it that far. I still dont like them adapters. Prefer have them direct PSU, just me. I got out of tech a decade ago, Excuse me for being a bit behind on this and that but that is something ive never actually checked, Ever haha

Maybe you could explain this....

http://imageshack.us/photo/my-images/841/imag0078bo.jpg/

i blame gigabyte, The Akasa PSU is still runnint 4 cards soundly. But im informed thats the ground!!!

P4Man:
Thanks for the image.  Nice visual summary.

Hint: to m3sSh3aD
1) The only 3V connection on any ATX power supply is in the 24pin MB connector.  The aux connector P4 showed above has been removed from the latest spec because MB honestly no longer needs 3V/5V.  The 3V and 5V pins on MB 24pin connector are also rarely used.  They just exist because at one time the CPU was powered by 3V and most of the MB logic by 5V.  However over time the power demands of CPU made that non-viable so CPU/MB/RAM are powered by 12V connector.  The VRM on motherboard step that down to the voltage required by all the components.
 
2) Even if the Peripheral connector (often called MOLEX connector) had a 3V (or 5V, or 7V, or 120V, or 24V, or 18.2V) connection you couldn't use it to power a 12V device.  If somehow you needed to power 12V GPU w/ a 3V rail you would need to use some device like a transformer to convert the 3V -> 12V.

You are wrong. IN the time you typed all that surely you could have googled pinouts

Well, I am on about them cables that plug into the 4 pin molex power connector. One card came with a single 4-pin to 6pin VGA, and the other had TWO 4-pin power molex's to 6-pin, so my point there is they STILL SUPPLY BOTH TYPES!

Whats that 3.3 and 5V on my power supplies then?

AKASA HCP 1200W - +3.3V 25amp & +5V 25amp which combined Max out @ 175W then 8x 12V 30amp rails which max out @ 1198 99Amps. If im not wrong the 4 pin molex and SATA power connectors all use either the 3.3V or the 5V. SO connecting a VGA card to the 4-pin molex doesnt run it through ANY of the 12V rails. Simalar situation i have on a OCZ 750W, Another AKASA AK1200 and so on. Unless im mistaken and the 4 pins are powered from the 12V rails. This im not 100% certain, More of a presumption in all honesty as i don’t see why you would run sata & 4 pin off the 12V rail? They really require 12Vs?

Correct me if im wrong, im sure you will Just something ive always thought and kept with proper connectors and skipped the converters COMPLETELY. Never liked the look of them :)PSU's are not my strong point, Only recently had to play around with multi PSU's and blown cheap PSU's at the start They provide power and corsair AX series and AKASA HCP are at the top of the pile(but not cheap) Thats all i need to know about PSU's Corsair have a slightly better SINGLE rail design with the AX1200.

I got a feeling im wrong on this but i just woke up and can't be bothered look. I'm sure you 2 will inform me what the 3.3 and 5V are for. I'm guessing the motherboard and its not passed through the 4-pin molex's power.

I've kinda got bored of arguing with you 2, Never thought that would happen haha. Putting my neck on a guillotine as well with this PSU thing, persumtion is the mother of all F**K UPS

None of which show 3V being used. Only 12V and ground.

  I believe Mess was refering to the miscolored cables in post #'s 1, 9 and 13...