Need advice on PSU behaviour

[Kuttoffer]

I recently upgraded my computer from an Athlon XP with 1 gig PC133 ram and an ATI 9700 pro, while keeping the rest, including the power supply. Its a Chieftec Hpc-420-302 DF with Active PFC. I looked up the UL numer - E144195 - and it turned out it is a Sirtech manufactured unit. Its rated at 5v/40A, 3.3v/30A (combined 220w) and a single 12V rail rated at 18A (216 w). My new hardware consisted of a dualcore 4000+ AMD x2, an used 1800XT, a m2n32 ws pro motherboard and 4 gigabytes of DDR2 ram. The problem is that when I use an application that uses the GFX card the voltage on the 12 V rail drops to 11.7v from 11.9 idling in windows and the power supply starts to give off a ticking/buzzing sound that varies in intensity and presence. I thought it was a hard drive before i discovered the huge voltage drop, which alarmed me since I know from reading power supply tests that a noticeable voltage drop usually preceeds a total failure. On my old system the 12 V line was stable at a wee bit above 12 volts. My current conclusion is that my entire system is more or less powered by that single 12 volt rail and my power supply is not faulty, just overloaded with next to no margin. Does anyone agree? I partially fixed this by downclocking my gfx card by 60%, now the voltage drop is to 11.8 and there is no ticking/buzzing sound when I play civilization. How much 3.3 and 5 volt amperage do you need in a modern system?

[burebista]

It's not overloaded it's crossloaded. ;)
Yor see, you have an ATX12V v1.3 PSU with power consumption focused on +5V and +3.3V which was perfect for your Socket A platform, but now you have a platform which need an ATX12V v2.x PSU with load based on 12V.

[SnooP]

It's not overloaded it's crossloaded. ;)
Yor see, you have an ATX12V v1.3 PSU with power consumption focused on +5V and +3.3V which was perfect for your Socket A platform, but now you have a platform which need an ATX12V v2.x PSU with load based on 12V.

true, also Chieftec :p I'd still say the 12V rail is a bit overloaded but. 18A aint much especially when its generic and a x1800xt videocard

How much 3.3 and 5 volt amperage do you need in a modern system?

5 or 10A at the most for each, unless your running lots of hard drives. this article should give you an idea, there hardly used.
http://www.silentpcreview.com/article265-page4.html

[burebista]

OK then. It's a mix of crossload and overload. :p

[Kuttoffer]

true, also Chieftec :p I'd still say the 12V rail is a bit overloaded but. 18A aint much especially when its generic and a x1800xt videocard


Is Sirtec/Chieftec a poor quality brand? Their prices are a bit lower than premium brands but on the other hand they do not have a brand name that they try to charge extra for. BTW, the supply is actually a RMA unit, the first died after 2-3 bootings. On the other hand, its from 03/32 judging by the sticker on it, so its possibly the previous sample perhaps suffered from the bad capacitator problem that was everywhere during this period.

[Kuttoffer]

FWIV I found my PSU on the www - or a close relative to it. I have a "302" with active PFC, this one does not have it.

http://www.xbitlabs.com/articles/other/display/thermaltake-psu-roundup_3.html.