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Author Topic: 4 pin molex to 6 pin pci-e connector. Word of warning  (Read 102479 times)
m3sSh3aD
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November 15, 2011, 11:01:37 AM
 #21

I just had a 6870 and 6950 replacements for old XFX junk and one came with single, one came with double power molex. Using the 3V line for your VGA cards isnt the wisest idea either. 12V rail/rails are there for a reason. 2 good 700-800 is better on a 4 card system than a 1200W with 3 PCI express that has to use a 3V for the 4th card.

Never experienced this but i never experience a Motherboard sending load beck through the GROUND to te PSU and killing itself and NEARLY the PSU at the same time. I use the PSU just to power the VGA cards now as the mobo connector is burnt to a crisp!!! Gigabyte are S**T, and so are XFX, be warned
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plastic.elastic
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November 16, 2011, 02:39:06 AM
 #22

I just had a 6870 and 6950 replacements for old XFX junk and one came with single, one came with double power molex. Using the 3V line for your VGA cards isnt the wisest idea either. 12V rail/rails are there for a reason. 2 good 700-800 is better on a 4 card system than a 1200W with 3 PCI express that has to use a 3V for the 4th card.

Never experienced this but i never experience a Motherboard sending load beck through the GROUND to te PSU and killing itself and NEARLY the PSU at the same time. I use the PSU just to power the VGA cards now as the mobo connector is burnt to a crisp!!! Gigabyte are S**T, and so are XFX, be warned

what the heck are you talking about?

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November 16, 2011, 02:49:33 AM
 #23

Nobody knows.  No videocard is powered by 3V so the post doesn't even make sense.  

Quote
Using the 3V line for your VGA cards isnt the wisest idea either.

Well it is little more than unwise, it is impossible.

Did you accidentally try to plug this into the video card?  It is the only connector on ATX powersupply which has 3V.  Grin
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November 16, 2011, 03:03:10 AM
 #24

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

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P4man
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November 16, 2011, 07:21:26 AM
 #25

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

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

m3sSh3aD
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November 16, 2011, 10:48:31 AM
 #26

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

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

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?Huh They really require 12Vs?

Correct me if im wrong, im sure you will Smiley 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 Smiley 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 Smiley 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 Smiley
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November 16, 2011, 10:55:01 AM
 #27

Correct me if im wrong,

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


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Gerald Davis


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November 16, 2011, 02:00:12 PM
 #28

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.
m3sSh3aD
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November 16, 2011, 04:31:18 PM
 #29

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 Smiley

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!!!
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Gerald Davis


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November 16, 2011, 04:39:00 PM
 #30

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 Smiley

Maybe you could explain this....

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

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?


m3sSh3aD
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November 16, 2011, 04:43:27 PM
 #31

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 Smiley

Maybe you could explain this....

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

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?




4 cards, 1 card on a powered extender. so 3x75=225 through PCIE, surely not enough to cause that. 5850's.
cicada
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November 16, 2011, 04:48:15 PM
 #32

The Akasa PSU is still runnint 4 cards soundly.

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 Smiley

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November 16, 2011, 04:53:46 PM
 #33

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

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.



m3sSh3aD
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November 16, 2011, 06:27:02 PM
 #34

just sapphire 5850 xtremes

Crazy issue
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November 16, 2011, 07:24:09 PM
 #35


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.

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November 16, 2011, 07:51:01 PM
 #36

If its not securely put in place, it could loosen itself and bad things might happen.

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 Wink  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?

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November 16, 2011, 08:01:33 PM
 #37

[edit] This thread got way off track Wink  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?

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.

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November 16, 2011, 08:10:43 PM
 #38

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.

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.


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.

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.

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November 17, 2011, 09:31:55 AM
 #39

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
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February 17, 2012, 07:39:00 AM
 #40

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.

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