Problems with power loading or overload maybe?

[imtheman0313]

I already know the answer to this riddle, I think, I just want to see if anyone else can figure it out. Think of it as a brain teaser. Here's the case:

Metal case, older
ECS GF8200-A mobo
Phenom II x4 940 (AM2+ version)
5 GB DDR2 cheapy style RAM
MSI Cyclone GeForce 460 768MB video
Rosewill (Capstone) 450W PSU (brand spanking new)
3x DVD-RW drives
1x WD IDE 350GB Hdd
3x SATA Hdd (various brands and sizes)

No Overclock currently, everything at stock speeds.
Tower style cpu sink with dual 80mm fans
3 USB ports in use (small items ie: keyboard, mouse, sd card reader)
2x 80mm front fans for Hdd cooling
1x 120mm x12mm? LED fan, top, exhaust
2x 120mm x 24mm? (big mamma jammas) side case intake
1x 90mm x30mm? (roughly, another biggun) exhaust behind cpu sink

Now for my conundrum. I run stress tests (checking for temps) at various points during the day to make sure the system can handle the coming apocolypse that is Arizona summer. So far no issues. Until recently, it seems.
As long as I leave the side cover and rear exhaust fan off, I don't have any problems. >>>If I put ONLY the two side 120s on, no problem.>>>>once I connect the rear fan, I get lockups, slow downs, and the bios reports AHCI issues (hard drives not loading up or reading correctly)

Now, I have run the numbers, and THEORETICALLY my system should have no issue. My question lies in the rear fan. It is currently connected to the board by the RPM and PWM wires, while the power and ground run out of the PSU directly. Does the Blue PWM wire actually use power? Or is it only a low level switch to ground (variable of course) Why does this one fan alone cause issues?
The PSU is rated at 450W, which in theory means it SHOULD be able to handle a teeny bit more. Either way, I don't seem to be surpassing its capabilities with the current hardware, considering that the dvd drives use negligible power on startup, and all the rest of the hardware comes out to around 400W under full load. Even taking into consideration startup amperage of the fans, should my PSU still not be able to handle this stuff?

 

[hunter315]

You have a fan connected to both the PSU and the motherboard? You have likely damaged your fan controller on your motherboard. You are only ever supposed to connect them to either the PSU or the motherboard. The blue wire provides a PWM signal to the fan to provide variable speeds in a more efficient manner than reducing the voltage, but since you are providing 12V to the fan and attempting to run PWM you are likely backfeeding power into the PWM on the motherboard.

This isn't a question of a fan being too much, this is a question of why did you do a dumb thing and try to power the fan from two sources and potentially damage your motherboard?

 

[imtheman0313]

The blue wire, when dropped to ground, turns off the fan. It is a signal into the mainboard of the fan. It's on the collector of a transistor on the fans main board. It is a low level signal. If I hook the fan to the MB, the traces for the fan power will melt. These things can only handle an amp, maybe. Each fan is 2.5 amps. It's not a MB issue. Nor is it a fan control issue. If the fan control circuit dies on the board, only the fans will be affected (unless the melting trace takes others with it of course).

I could very easily hook the blue wire to a 555 circuit w a pot and control the fans that way, but figured since the board has the capability to do so, there was no need.

The issue is in the PSU itself (maybe not necessarily "inside", however).

I do thank you for your thoughts, but wag a finger at the assumption that I do not know what I am doing. I very much Know the problem, as I said, this is more of a get the info out there brain teaser kind of thing for the community.

Also, more information. If "hot" plugged, the errors that accrue are memory errors. The cable set that the fans are plugged into is the molex set (you know, the 4 pin IDE power connectors) The fans plugs go on the end, with 4 total connectors to power various fans (most of which are 2 wire, so no speed control there).

 

[imtheman0313]

Nobody has any other ideas? Ok, fine. I'll just post the solution then. The problem I have with the fans, is this: while theoretically I do have enough power in the psu to supply all the fans, and then some, they are all wired coming off the same line. So, think about it. 5 fans, all wired to one cable, on which a HDD is also powered. The fans are all connected by themselves on their own separate "tie-in" kind of connector. Off the molex line its a male>female connector with 2 wires exiting for fan power.

All these different connections, and such high power devices on one line, the wire cannot handle it. It's just a tiny little 16ga wire comin out of this psu. The voltage drops on that wire only when all the fans are connected, and the HDD doesn't have enough power to stay on all the time.

Very simple.....lol

Just info for anyone with a similar issue. Remember to always split up your high power needs between different cables