2 power supply questions...

[daveleau]

Hi everybody!

I am having a problem with my power supply. It is overheating. I have a bunch of stuff running in my system including 2 7200rpm hdds and 2 cd-rom/rw drives. I was wondering if I can run and external PS (200W AT power supply) to run 2 of my drives to reduce the strain on my current 300W PS (not sure if it is dying yet or not...the fan seems to be working fine). Will this cause any electromagnetic problems through a pressed wood desk? Will it cause any problems in regards to management by the system? If I run my 2 RAIDed hdds of a PS NOT connected to the mobo, will this cause a problem?

Thanks
Dave

[Roy]

I think it's a darn good idea! http://sysopt.earthweb.com/forum/smile.gif

Since you're only using the brute force 12V part of the supply, I don't foresee any problems. Since they're both plugged into the same U-ground outlet set, their cases will be "connected" and their "ground" references should be the same.

I'd say, go for it! It's the same as hooking some of the drive motors to a car battery. Hmm ... another idea. http://sysopt.earthweb.com/forum/wink.gif

[tonym]

Dave,

Please explain "overheating"! And if you could, please list all the components that your PSU provides power to!!

I have systems that have Athlon 750's, 512MB, 2 HDD's, a Jaz, a ZIP, a CDRW, a floppy, a video card, a modem, a NIC and a SCSI card. All being supplied by a 300W PSU. And I've theromcoupled the heatsinks in my PSU (I'm anal retentive!), and I don't see a temperature greater than 55°C, even when the ambient is 35°C)

Your average PSU is about 80% efficient at half-load and 70% efficient at full load, so if you draw exactly 300W then the supply will dissipate (300/.70)-300 = 129 Watts! If you increase the available power of your supply, say to 450W, you will move up in efficiency and then you will dissipate (300/.80) - 300 = 75 Watts. You've eliminated 50W of heat loss just by upping the PSU rating. This is an often overlooked factor in PSU selection!

Now, you want to add an auxiliary AT PSU to run your disks. It WILL work electrically...so long as they share a common ground (return). HOWEVER, if this PSU external and the wires pass through the enclosure, then you can run into a whole bunch of EMC/EMI/EMF/RFI problems for your system and radios and TVs in your general vicinity. The operating frequency of the PSU is in the range of 75-200kHz, depending upon manufacturer. This switching frequency and harmonics will disrupt AM radio if not properly shielded (the output leads are intended to be in the computer's "enclosure port"). The mobo, PCI card and the disks all have oscillators in the 10-50MHz range. These frequencies and their harmonics will disrupt CB/police/weather/TV/FM bands.

And having "raw" DC lines outside of the case can lead to potential ESD (static) and conducted disturbances from other sources. An example of this is every time a taxi goes by and keys his mike, your PC reboots! It can happen!!

You can try this and it MAY work fine for you, but your neighbor without cable may lose channel 5 or their AM radio band because of your PC Frankenstein! My advice to you is to stay away from the external PSU and buy a 450W or greater PSU that fits right inside the case.

Tony

[Donkey]

Why not get an external hard drive bay that houses the PSU and hard drives in the same unit then just run the data cable back into your PC case.

[Stan]

Mmmm... I am quite surprised that your PSU is overheating.

I also have a 300W PSU and no problem so far.
My box contains:
- 2x PIII600E
- 2x 128MB SDRAM
- 4x IBM 22GXP (7200 rpm) on a FastTrak RAID
- 1x Pioneer DVD 6x
- 1x Asus CD 50x
- 1x LS-120
- 3x 8cm internal fans
- 6x 4cm HD fans

Using a 2nd PSU to connect the 2 HD looks like a good idea to me.
Make sure to switch on the 2nd PSU before booting up the PC.

Stan

[This message has been edited by Stan (edited 07-28-2000).]

[daveleau]

Thanks guys, Here is the link to the actual problem I am having: http://sysopt.earthweb.com/forum/Forum2/HTML/008709.html
Dave

BTW, would running your case w/o the cover also cause the disturbances?

[Stan]

See my suggestion here (http://sysopt.earthweb.com/forum/Forum2/HTML/008709.html)

Stan

[This message has been edited by Stan (edited 07-28-2000).]

[daveleau]

Hey guys, I posted my problem in tech support since this was originally trying to see if the dual PS was possible. But here are my system specs in case you need them for this...

Cel 2 566 @ 910 (1.70V, 107 fsb and constantly <50C)
Abit BF6 (SH BIOS-Latest)
IWill Slocket 2
2-- 20GB WD 7200 rpm Expert hdds
Fasttrak RAID modified from Prom ATA66
384 MB Infineon CAS 2 PC100 (3 sticks of 128MB)
Kenwood 52X CD-ROM
HP 8250i CD-RW
FDD
G400 Max Dual Head
Sound Blaster live Value
3Com and Netgear 10/100 NICs
USB Zip 100 Drive
300W generic PS (3 months old!)
2 80mm fans
2 486 cpu fans
1 Golden Orb

I say it was overheating b/c the air from the PS was much hotter than I have ever felt coming out of the back of the PS. I am now not completely convinced but leaning toward it being a PS problem.

Thanks
Dave

[Eli]

My power supply's tendancy to overheat got so much worse when I added my Voodoo 3 2000 a couple of weeks ago as well. The only AT supply I could find was another 250w one, and it was cheap, so I tried it. No more problems. I'd say that if you have an extra one give it a shot. It's possible that the 200w PS could be tougher than your 300w.

To run two power supples, wouldn't you need to add some sort of load to the AT connectors on the second one, in place of a motherboard? I remember discussions about using an extra PC power supply to run R/C battery chargers and they had to wire in a couple of resistors or something. I wasn't paying very much attention at the time...

[tonym]

Dave,

Yes, operating without a cover would potentially cause disturbances! That's why manufacturers haven't taken the step to full plastic cases (look at the Mac closely, it's a steel box within a pretty plastic case!!). the FCC gets pissed if the PCs are unshielded!!


Tony