Cheap PSU: Piece of junk or semi-decent?

[Behemot]

Re: Cheap PSU: Piece of junk or semi-decent?

Yeah it's tending to crossload it seems. High load on +3,3/+5 V boosts +12 V. Anyway, down to 4,75 it's still within specs.

[goodpsusearch]

Re: Cheap PSU: Piece of junk or semi-decent?

Reading on an empty molex the multimeter says 4.86V at idle, 4.81V full CPU load on +5V.

On +12V it is 12.32V/12.43V idle/load (+12V voltage increasing under load? ).

It's a venerable PIII slot-1 440BX mobo. Runs fine but there are occasional hang-ups, screen just frozing (no BSOD, no reboot).

Typical results from a crossloaded psu. Not good, but not terrible. Still inside the ATX specifications.

[Behemot]

Re: Cheap PSU: Piece of junk or semi-decent?

^You pay the beer bro

[goodpsusearch]

Re: Cheap PSU: Piece of junk or semi-decent?

^You pay the beer bro

Here you are

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

Those motherboard sensors are never right.

Did some research on the subject and found this little 2005 study: Multi-meter vs. Motherboard: A Study of Voltage Readings

Seems the mobo reporting different (lower) voltage than the multimeter is the norm.

However the idea of mobo voltage sensors 'reading wrong' is a bit disturbing, since the mobo voltage sensor (actually a current sensor it seems) is monitored by the onboard PWM controller that governs the VRMs.



Well today I learnt what crossloading is . For the benefit of other newbies like me there is a good explanation of crossloading here.

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

This ancient PIII system draws very little AC from the wall, 68W at idle and just 90W at full CPU load. Considering the cheap 'TOOQ' PSU has probably a low efficiency, the real DC draw must be even less.

However I've noticed that the stand-by draw (comp shut-down but still plugged to wall) is relatively high; the dinosaur draws 3W, vs 1.5W for a modern comp with quality PSU.

I'm wondering if the 5vsb 2N60 mosfet's high RDS(on) of 5Ω could be the reason.

I've seen that a forumer replaced his 5Ω 2N60 with a 1Ω P6NK60Z; I wonder if his stand-by draw decreased afterwards.

This PIII is just for occasional retro-gaming and spends most of his time in stand-by, so lowering the stand-by draw could be interesting.

Go on, swap switching transistors I bet there are 13007 now? Try 13009 or something fatter (2SC2526 are common too).

What would I get with that switch? Even if this PSU can only reach 250W before , that's still plenty of roof for this frugal ~100W tops old comp. So I don't think I have a need for more powerful transistors, unless I'm wrong.

I would like (if possible) to improve in efficiency, reliability, and comp stability (crossloading, ripple, noise).

[PeteS in CA]

Re: Cheap PSU: Piece of junk or semi-decent?

However I've noticed that the stand-by draw (comp shut-down but still plugged to wall) is relatively high; the dinosaur draws 3W, vs 1.5W for a modern comp with quality PSU.

I'm wondering if the 5vsb 2N60 mosfet's high RDS(on) of 5Ω could be the reason.

I've seen that a forumer replaced his 5Ω 2N60 with a 1Ω P6NK60Z; I wonder if his stand-by draw decreased afterwards.

Depending on the balance of power consumed due to R(D-S On) vs. the power for driving the Gate capacitance, that might improve the efficiency of the +5V Stby a little, but it might not be noticeable. My guess is that most of that 3W is going to the MB. And 1.5W vs. 3W isn't that much heat. Probably not worth the bother.

Changing the 13007s to 13009s might improve the efficiency some, due to lower V(CE Sat) and better beta at the operating I(C) (also improving the V(CE Sat), but probably not worth the bother for the reason you mentioned.

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

Thanks Pete.

What mods would yo do to this 'TOOQ' thing for a PIII?

If this cheap PSU is not worth the hassle, could you recommend any decent modern PSU for a PIII system? Maybe something like an Antec VP-450, or a Corsair GX430 V2, or a Be Quiet Pure Power L7 300 could suit a PIII well?

[Behemot]

Re: Cheap PSU: Piece of junk or semi-decent?

For single processor system, basically any of them as they usually offer arround 30 A on +5 V. For (overclocked) two CPU system, none as that still may not be enough.

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

Did a small brute-force-approach crossloading mitigation experiment. Plugging a car 12V/21W light bulb to a molex the voltages do improve and move closer to the mark .

______No bulb at +12V, idle/load _____ Bulb at +12V, idle/load

+5V ············ 4.86/4.81 ··························· 4.91/4.86
+12V ········· 12.32/12.43 ························ 12.27/12.37


But to waste an extra 21W in heating the system is totally crazy .


Does anybody know if what a Radeon 9800 Pro sucks through this molex header ...

... is +5V, or +12V juice?

[Behemot]

Re: Cheap PSU: Piece of junk or semi-decent?

Could be both. From the orientation I believe left pin is +12 V, right is +5 V. Take your multimeter set to diode tester and find from which pin does the current flow through those chokes on the input sides of the VRM's in there - it should end on it's input capacitors. I can see 16V cap in there, so it definitelly uses +12 V, probably for core, the question is whether it does not use +5 V for memory. It could draw power through AGP too, there is +5 V present and it won't take much for memory chips.

[tom66]

Re: Cheap PSU: Piece of junk or semi-decent?

I dunno why it's such a big deal though. A half-decent supply will meet the 5%. A really good one will be 3%. But I've had a computer that still boots properly with just 9V on the 12V rail.

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

I dunno why it's such a big deal though ...

Besides the fact that I like to fiddle and experiment , I'm finding the system is more stable with the bulb moving +5V & +3.3V voltages closer to the mark. It's a guerrilla modified and crazily overclocked comp and every bit helps.



Did my first ever recap on the 'P4' PSU .

-> LARGE


The little bugger with its cracked domed top excreting 'Agent Orange'.




Replaced it with the closest I could find amongst the loot scavenged from an old broken huge CRT monitor.




The replacement is 1000uF 16V 85C, against the original 1000uF 10V 105C.






Again in a most amazingly way considering my solder skills, when I plug it to the wall the thing not only doesn't explode, but seems to work OK with coherent voltages .

I'm looking for what you call 'a sacrificial comp' for the supreme test.

[Th3_uN1Qu3]

Re: Cheap PSU: Piece of junk or semi-decent?

I wouldn't keep an 85C cap in that place, it'll be toast quickly. Also, almost all 85C caps are general purpose, not low ESR, so the ripple may be out of check.

For a PIII i would try and grab a hold of an old Hipro. I got 5 of them, fixed up two, and one i kept for my own dual-PIII. I never even recapped it fully - most of it has still got the original Su'scon caps which aren't the greatest, but it runs without a single hitch. I used to have a "Xilence" 460W in there, but once i got the dual Tualatins, they would use so much 5v and 3.3v that the SATA hard drive would stop. No trouble with the Hipro.

[Behemot]

Re: Cheap PSU: Piece of junk or semi-decent?

So no 12-to-5 DC-DC after all? You got the Hipro pushing it?

[PeteS in CA]

Re: Cheap PSU: Piece of junk or semi-decent?

The replacement is 1000uF 16V 85C, against the original 1000uF 10V 105C.

Concur with Th3's comment! That 85C cap won't last long as the output cap in a power supply. It's 2004 vintage, so I would get 1000uF, 10V United Chemicon (= Nippon Chemicon) LXV, LXY or LXZ series parts or Nichicon PM, PJ or PW series parts (or Panasonic FC series) in there as soon as you can get some from Farnell or whatever distributor sells in Spain.

[Th3_uN1Qu3]

Re: Cheap PSU: Piece of junk or semi-decent?

So no 12-to-5 DC-DC after all? You got the Hipro pushing it?

Yes. No issues since i put that PSU in. I'm pondering on getting one of brethin's HD4670s... The only other thing besides that, will be a full poly mod on the mobo, and adding DIP switches for manual Vcore on each CPU.

With those two additions, i've maxed out that rig, nothing else can be added. Maybe installing Windows 7 instead of XP... It's likely to keep up for a few more years, then i'll just make it a server.

[Behemot]

Re: Cheap PSU: Piece of junk or semi-decent?

If there is AGP 4x, than it's not a problem. I am unfortunatelly limited with AGP 2x on my ABIT BX133-RAID. But I have Radeon 9800 Pro already sitting here, just didn't installed it yet as I did not turn that thing on for half a year. Playing tanks, no time for old RPGs

To not be OT, got one of those Fortrons we are talking in built quality thread in there.

[TELVM]

Re: Cheap PSU: Piece of junk or semi-decent?

Well definitely the 21W light bulb patch works , I'm now unable to hang the Tualatin no matter how hard I torture it.

But I hate to waste those 21W in HEATING the system. How could we continuously draw ~20W from the +12V rail in a somehow more beneficial way?

... That 85C cap won't last long as the output cap in a power supply ...

Excuse the potentially noob question: What exactly will kill it? The heat?

[Th3_uN1Qu3]

Re: Cheap PSU: Piece of junk or semi-decent?

If there is AGP 4x, than it's not a problem.

Yes. ASUS CUV4X-DLS, that's the very reason i got this board.

Well definitely the 21W light bulb patch works , I'm now unable to hang the Tualatin no matter how hard I torture it.

But I hate to waste those 21W in HEATING the system. How could we continuously draw ~20W from the +12V rail in a somehow more beneficial way?

There are a few ways around this. Beef up the rectifiers on the 5V rail, so there is less voltage drop. That way 5V should stay in spec. Also you could alter the feedback ratios, so that 5V is treated as more important than 12V, but that would cause 12v to jump even higher.

Excuse the potentially noob question: What exactly will kill it? The heat?

Main cause would be heat, yes. There is also ripple current that the cap has to handle, which causes self-heating. This, along with the heat coming from the rest of the components, will quickly cook that 85C cap.