Most PSUs have internal current sense resistors, do they not?

SRQ wrote:

If you can source a better one that's equally quiet on newegg or somewhere by all means.

I haven't looked at new PSUs in a while and it's harder to find a good one for old systems than it used to be.
This one looks pretty good. All Jap caps. Good reviews. Fair price.
They have it listed twice and it's $20 more in the other ad.
http://www.newegg.com/Product/Product.aspx?It … N82E16817151094
http://www.hardwaresecrets.com/seasonic-s12ii … -supply-review/
http://www.jonnyguru.com/modules.php?name=NDR … =Story&reid=185
If I come across any others I will edit-add here to keep it in one place.

gdjacobs wrote:

Most PSUs have internal current sense resistors, do they not?

If you are indirectly asking about over current or over voltage protection most supposedly do but it doesn't always work right.
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The direction I'm wondering about is Vsense across the resistor (if it exists), directly extracting the rail currents.

gdjacobs wrote:

The direction I'm wondering about is Vsense across the resistor (if it exists), directly extracting the rail currents.

I'm not 100% sure but I think they do it by measuring the voltage drop across a shunt made out of a short piece of resistance wire.
So ~sort of~ a resister.

That's just how your multimeter does it.

Semi-related: The CD drive on this thing gets /really/ loud. Sometimes it spins up and then passes a threshold where there's a whine. I've duct-taped paper towels to it in a weird sort of half-assed dampering system which helps- but it's stil there, just slightly quieter. Is there a way to limit it to 30x or something?

SRQ wrote:

Semi-related: The CD drive on this thing gets /really/ loud. Sometimes it spins up and then passes a threshold where there's a whine. I've duct-taped paper towels to it in a weird sort of half-assed dampering system which helps- but it's stil there, just slightly quieter. Is there a way to limit it to 30x or something?

There are several utilities around that do that but they don't necessarily work on all drives.
I never tried one personally so IDK how well they work. You just have to try them.
https://www.google.com/#q=limit+cd+rom+speed

Did you look at the drive I linked you to earlier?

You linked a drive? I looked at the PSU- it seems a solid bet, thanks.

SRQ wrote:

You linked a drive? I looked at the PSU- it seems a solid bet, thanks.

Oops. Meant PSU.

For DOS try CDBQ
For Windows 9x just get an old version of Nero DriveSpeed.

SRQ wrote:

Semi-related: The CD drive on this thing gets /really/ loud. Sometimes it spins up and then passes a threshold where there's a whine. I've duct-taped paper towels to it in a weird sort of half-assed dampering system which helps- but it's stil there, just slightly quieter. Is there a way to limit it to 30x or something?

Newer ones are generally more silent.
The really loud ones stem from the time when every manufacturer was trying to get the highest X-speed rating on the front bezel of their CDROM drives. The later ones are more silent, but I found one might as well use an older DVD drive as those are generally more silent.

On another note, one could see the 'loudness' of these CDROM drives as a 'feature', kinda like the FX 5800 😁
Btw, the 24x drive I used was still not as superloud as the 40x and faster ones, except for the newer 52x ones maybe (the 52x ones which were made at the same time the older DVD drives were made).

Tetrium wrote:

On another note, one could see the 'loudness' of these CDROM drives as a 'feature', kinda like the FX 5800 😁

Or the F-18.

I don't remember too many noisy ones but there were a rare few were I got the urge bolt down the case to keep it from from going airborne.
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The FX doesn't come close to some Socket A/370 CPU coolers I have. I'm talking 7000 rpm or something silly 🤣

PhilsComputerLab wrote:

The FX doesn't come close to some Socket A/370 CPU coolers I have. I'm talking 7000 rpm or something silly 🤣

Dragon Orb? 😜

But the older Intel s370 ones were pretty bad also and not because of the noise volume, but because of the penetrating whining they made me endure 🤣!

PCBONEZ wrote:

Or the F-18. […]
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Tetrium wrote:

On another note, one could see the 'loudness' of these CDROM drives as a 'feature', kinda like the FX 5800 😁

Or the F-18.

F-18.jpg

I don't remember too many noisy ones but there were a rare few were I got the urge bolt down the case to keep it from from going airborne.
.

I'd love to have such power inside a metal box standing next to my monitor! 😁
...but not if it also makes me deaf 😵

tayyare wrote:

I think power requirements sometimes over exaggerated. I had a PIII 1000 Coppermine rig that I recently took apart for another b […]
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I think power requirements sometimes over exaggerated. I had a PIII 1000 Coppermine rig that I recently took apart for another built. It was my first attempt for a retro build, even long before I started involving with vogons, so it was some kind of a freak without no real practical purpose. The PSU of that machine was a an old and tired Aopen FSP300-60ATV with following specs:

+3.3V 28A
+5V 30A
+12V 15A
-12V 0.8A
-5V 15A
+5Vsb 2A

And the specification of the machine was as follows:

Intel Pentium III 1000
Gigabyte GA-6VXE7+ + 1GB RAM (512MB x 2 Kingston PC133 SDRAM)
Matrox Millenium II 4MB PCI + 8MB Add-on VRAM
3Dfx Voodoo 3 3000 16MB AGP
3Dfx Voodoo 2 12MB PCI x 2 SLI
Sound Blaster AWE64 Gold ISA + SIMMCONN + 32MB 72 pin SIMM
Adaptec AHA-29160 PCI
Surecom EP-325 Realtek 8029AS PCI
Maxtor DiamondMax Plus 8 30GB ATA
Maxtor DiamondMax Plus 8 30GB ATA
Samsung SpinPoint V40+ 40GB ATA
Maxtor Atlas 10K V 73GB SCSI
Maxtor Atlas 10K V 73GB SCSI
Maxtor Atlas 15K II 73GB SCSI
Fujitsu MAP3367NP 36GB SCSI
Seagate ST33607LW 36GB SCSI
3.5" Mitsumi 1.44MB
5.25" Teac 1.2MB
LG GSA4040B DVD-RW IDE
HP Surestore DAT8 Tape Backup

In short; 8 HDDs (of 5 were SCSI), 2 FDDs, 1 optical drive, 2 RAM sticks (I also used with 3, when it was required with XP), 7 cards (two of them with additional RAM upgrades), 1 streamer, 2 very high rpm fans, 1 AMD socket 754/939 stock cooler, and the usual keyboard, mouse, joystick, usb card reader, etc.

I never had any power related issues at all, during its 5 year life. And especially for the first 3 years, I used it a lot. Same power supply is powering my new P4 Prescott build (4 HHDs, two display cards, 3 additional cards, two DVD drives, a floppy, 4 1GB DDR 400 sticks, etc.) at the moment.

Sorry this took so long. Info on some of your parts was hard to find and I kept getting sidetracked.
The proper way to spec a PSU is to use the sum of the max component values against the max rating of the PSU.
This way in normal operation you are well below the PSUs max and you won't pop anything when you start up.
You were pushing it. Presumably sequential drive spin-up saved you when you started it up.

Wow!

Thanks a lot for the deep analysis. I as not expecting this.

tayyare wrote:

Thanks a lot for the deep analysis. I as not expecting this.

I have an Engineering background and I've analyzed a lot of things to that level (over years) which is why I get miffed when people that haven't try to tell me I dunno what I'm talking about.
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I started doing that for PSUs because the 2 and 3 way redundant PSUs that come with server chassis are serious over-kill for me and I needed to find consumer-retail type PSUs that could handle the load without needing 2 or 3 power cords.
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I hope it's obvious now why I said at around 25 amps of 5v to be safe with a 5v CPU gaming system.
20a might work initially for the basic system but by the time you start adding RAM, drives and add-in cards it's really easy to go over 20a.
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I have been restoring an old P3(Socket 370) / Voodoo 3 system that I spent many hours on when I was younger and faced a similar predicament to you.

The PSU (LC-B350ATX) was giving off a whine and I decided a new one was in order after checking the voltages with a PSU tester. I suspect that a faulty PSU may be what originally killed the system, circa 2004, as I had to recap the mobo to get it to boot.

In the end I opted for a Seasonic Platinum 400 Fanless (SSP400FL). Modern and expensive, but here's my reasoning (in priority):

• It's an ATX mobo this is an ATX PSU...what could go wrong?; 😊
• The 400W supply seemed ample for a build of this era;
• Didn't know/have time to research 'good' vintage PSUs;
• Happy to recap a mobo, but tinkering with a PSU's Amps / Volts is out of comfort zone;
• If it didn't work I could use it in modern build I am planning;
• SSP400FL seemed to have good voltage regulation features (which should be vastly improved from the era);
• SSP400FL is modular;
• SSP400FL is fanless.

After subsequently reading this thread and PSU - bust the myth, I didn't realise I could have fallen foul of the -5V issue, since this and most modern PSU doesn't output that voltage. Thankfully since I don't have ISA (Tom's Hardware Thread) on the mobo and the +3.3V & +5V output is sufficient, the PSU is a winner (+3.3 = 20V / +5 = 20A / +12V = 33A).

I haven't stress tested it yet with heavy gaming, but all in all very happy so far whilst it has been running Lubuntu doing various tasks. It's dropped the noise of the build considerably and the system is much more stable. I will be looking into heat sinks and fans next.

Even if I could have chosen a better option, my research did lead me to this forum though! 😎

TLDR: In a similar predicament to you and I got a Seasonic Platinum 400 Fanless for my P3 Voodoo3. It's great! I don't have any ISA slots so didn't need -5V, and haven't maxed out the ampage on the +3.3 or +5 volt outputs.

What I've learnt: You can use a modern PSU but check the ampage of the +3.3 or +5 volt output is sufficient and see if you require a -5V output.

PhilsComputerLab wrote:

What are your thoughts on something like this?

http://www.amazon.co.uk/DIGIFLEX-Power-Supply … k/dp/B004IO5CT8

This one only measures voltage, but maybe there is one that does current?

I have this. The build quality isn't fantastic but it does the job well and I have successfully identify failing PSUs with it in the past.