PSU Danger questions...

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Silhorn

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May 10, 2008
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Hopefully this will be my last PSU questions

1. If my system is rated to be around 350w and i get a not so good
brand psu at 500w would it still be able to run "ok" since it is 150w extra?
What would be the main side effects of not getting a good quality psu?

2. I read somewhere once where some guy used his psu for the first time and his hardwares blew up (hdd,mboard,etc)
When running psu for the first time are there special precautions or steps i can do to
make sure it doesnt happen to me?.

If i gave you this information from a psu would you be able to tell if it is good or not?
PC ATX Power Supply 500W with SATA & 120mm Fan

• Specification compliance: ATX12V v2.2 & EPS12V v2.9
• Supports the latest Intel & AMD sockets
• PCI express & serial ATA ready
• Double forward converter circuit
• High efficiency and reliability
• Low ripple & noise
• Super low noise fan control
• Short circuit protection on all outputs
• Over voltage protection
• Over power protection
• 100% burn in, high temperature cycled on/off

Electrical Specifications:Input Frequency: 47/63Hz
In-rush current, cold start 100A max
Hold up time, full load 100ms, typical
Efficiency: at normal input voltage >70%
at AC 110V 60Hz 75% typical
at AC 220V 50Hz 78% typical
Optional 80PLUS at normal input voltage >80%
Line regulation: ±1% typical
Load regulation: ±5% typical
Cross regulation: ±5% typical
Ripple/Noise 1%
Standby mode <5W
MTBF, full load @ 250C amb, Excluding the DC fan: >100K hrs
Power Factor Correction: active PFC 99% typical




 
mi1ez

mi1ez

Splendid
Jul 17, 2007
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1)A good PSU from a known brand is preferable to prevent (2) from happening!

"Optional 80PLUS at normal input voltage >80%"

How can 80PLUS be optional? It's a certification!
 
jsc

jsc

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Jul 14, 2004
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1. If my system is rated to be around 350w and i get a not so good
brand psu at 500w would it still be able to run "ok" since it is 150w extra?
What would be the main side effects of not getting a good quality psu?
1a. Maybe. 1b. Anything from instability to a catastrophic failure that takes the motherboard with it.

2. I read somewhere once where some guy used his psu for the first time and his hardwares blew up (hdd,mboard,etc)
When running psu for the first time are there special precautions or steps i can do to
make sure it doesnt happen to me?.
That doesn't happen often. Usually the PSU is DOA. About the only thing practical you can do is to test the PSU on an old "junk" system. And that's not certain. A PSU may be fine under a light (30%) load or a medium (50 - 60%) load, but failure a heavy (80 - 90 %) load. The little $15 - $25 PSU testers will detect a DOA PSU, but they do not test the PSU under a real load. I have one and I put together a 200 watt load for it with some power resistors and an old P4 heatsink. OTOH, I have been doing this for a long time. But for the price of a cheap PSU and a PSU tester, you should simply buy a good PSU.

If i gave you this information from a psu would you be able to tell if it is good or not?
PC ATX Power Supply 500W with SATA & 120mm Fan
-- Block of specifications (but none of the useful ones) follows
No. Need brand and model of PSU. And specifications of the system you are going to power with it.

If you click on my "more information" line, you will see that I am in Saudi Arabia. Saudis will run around and ask different people the same question, hoping to sooner or later hear an answer they like.

And sooner or later, someone will post, "Yeah. I've been using cheap PSU's for years and I've never had a problem." For the rest of us, there's a reason why we recommend the more expensive Tier 1 - 3 PSU's.



 
M

mike99

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Sep 9, 2006
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How did you reach that 350W figure? If you paid $30-40 it will be very light in weight and be unstable or likely to fail. For 500W PSU you should expect to pay $90 or more. Good PSUs have overcurrent and overvoltage cutout circuits that work, cheapies don't, which is why they can go 'BANG' and take out other components. Many cheap PSUs either tell lioes about spec, or quote 'PEAK' power, not MAX (sustained) power.

Mike.
 
jsc

jsc

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Jul 14, 2004
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Unless you find it on sale.

And for a given power rating, a good PSU will be heavier than a cheap one. Another thing to look for is a spec that says, "Full rated power at 50 C.". Cheap one generally do not specify, or they specify 25 C. The 50 C. specification is difficult to meet.
 
S

Silhorn

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May 10, 2008
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ok I just found some extra info on this psu

This is for the 350 to 400w ranges but it is the same model so it
should be similar

Input Voltage 230Vac (180-264);115Vac(90-132)(select)
Frequency 47Hz-63Hz
Current 3.0A (MAX)At 230Vac; 6.0A (MAX) At 115Vac
Model Voltage +5V +3.3V +12V -5V -12V +5VSB
ATX300 Maxload 30.0A 20.0A 15.0A 0.5A 0.5A 2.0A
Max Output 400W - Output - 300W -
ATX350 Maxload 30.0A 28.0A 15.0A 0.5A 0.5A 2.0A
Max Output 450W - Output - 350W -
ATX400 Maxload 35.0A 30.0A 18.0A 0.5A 0.5A 2.0A
Max Output 500W - Output - 400W -
Power Good Signal 100-500mS
Power Fail Signal 1mS MIN
Hold-Up Time 16mS
Line Regulation 1% MAX
Over Voltage +3.3V: 4.2V,+5V: 6.8V,+12V: 14.2V
Short Circuit All Output to GND
Hi-Pot >Voltage 1500ac, Time 2-3sec. cut off current 10mA MAX

What should i be looking at and at which amounts
 
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mike99

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DOA - Dead On Arrival.
I've not much idea what you should be looking for as you haven't listed yourspec. You need to give name AND model of PSU. The ones you listed may be old designs as they have high output on 3.3V which is not used much by current motherboards. Many video cards give a minimum 12V current rating for typical system using that card.

Mike.
 
Crazy-PC

Crazy-PC

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Mar 29, 2008
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Answer for Q1) Not sure, it depends on the claimed 500Watt is peak power or continuous Power, we just could say normally would be OK for 500Watt PSU for 350Watt system if the claimed 500Watt is peak power for a short period of time.
Answer for Q2) Not good enough as the specification shall specify the current available for individual voltage like current for +3.3, +/- 5V, for +/- 12V etc.... which is as well as your 3rd post stated. However the specification of PSU shall stated what is the maximum total power output on both 5V +/-12V etc that can be provided by the PSU.
 
jsc

jsc

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Jul 14, 2004
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Well, it would be useful IF you have one of those inexpensive PSU testers. Within their limitations, the testers are quite handy.

The PSU load was technically a trivial problem. 12 volts across a 1 ohm resistor causes 12 amps to flow through it = 144 watts. 5 volts across a 1/2 ohm resistor causes 10 amps to flow through it = 50 watts. Total - 194 watts

Aluminum housed wire wound power resistors need to be mounted on some sort of heatsink. In my junk box, I had a couple of P4 heatsinks that I had been saving for ... well, I don't know. Because that's what packrats do. They save stuff.

The next problem was to mount all this on the back of a P4 heatsink. My first idea was to use three 50 watt 3.0 ohm resistors in parallel for the 12 volt load and a single 50 watt 0.5 ohm resistor for the 5 volt load. Four resistors will not fit. So I used a pair of 2 ohm resistors in parallel. I'm overloading them by about 50%, but I figure that they are running only for a short time, not continuously. And I mounted a small fan on the fin side to help with cooling.

I used small self-tapping screws to mount the resistors and wired the 2 ohm resistors in parallel and wired the fan across them. I took a pair of 4 pin male Molex connectors from my junk box and wired them in parallel, then connected them to the resistor assembly Yellow and Black wires to the pair of 2 ohm resistors (12 volt load) and red and black to the 1/2 ohm resistor (5 volt load).

To use, hook up a couple of Molex (drive) connectors from the PSU to the load before you connect the tester to the PSU. I wanted to parallel the input to the load because I did not want to pull 10 or 12 amps through 1 set of drive cables.

The voltages are pretty safe, but you are working with fairly high current levels. :non: If you are not comfortable soldering, do not try this.

Obviously, the parts are not critical. You need appropriate resistor values and wattage ratings for the size of load you wish to build. My parts source was Mouser Electronics (USA).

Need two Mouser Part # 284-HS50-2.0F 2.0 ohm 50 watt Aluminum housed WW resistors- about $3.20 each
Need one Mouser Part # 284-HS50-0.5 0.5 ohm 50 watt Aluminum housed WW resistors- about $4.70 each

They are on page 645 of the Mouser online catalog.
 
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