Found a brand new Comp USA PSU

[tom66]

Re: Found a brand new Comp USA PSU

A good power meter can measure down to 0.01 PF. Actual power factor of a standby circuit is typically 0.3 to 0.5PF.

[Behemot]

Re: Found a brand new Comp USA PSU

My meter shows that but I won't put my hand into fire for the accuracy. Especially when we are talking about harmonic distortion, not phase shifting.

[tom66]

Re: Found a brand new Comp USA PSU

I'm not sure what you mean. Measuring power factor is easy. Simply measure current using a high speed ADC, use a DSP to compute RMS current and multiply by RMS voltage (in the same way) which gives you reactive power in VA. Then measure power by integrating voltage and current, and divide the two to get PF.

If you use a cheap meter you're going to get poor results but that's how some of the equipment that the company I work at makes, does it.

[Behemot]

Re: Found a brand new Comp USA PSU

Masuring the current may not be that easy if the drain is realized by harmonics spikes with base at say several tens of kHz and than many more ending somewhere in MHz range.

[tom66]

Re: Found a brand new Comp USA PSU

There is basically zero energy beyond a few kilohertz. It's all shunted to ground by the Y- and X-caps anyway.

[Behemot]

Re: Found a brand new Comp USA PSU

If they are present… It clearly has *some* impact if the THD is such problem, right?

[Pentium4]

Re: Found a brand new Comp USA PSU

Regardless of efficiency here is why 2 transistor 5VSB sucks, this one had the critical cap fail. It killed an Intel 775 motherboard

[everell]

Re: Found a brand new Comp USA PSU

Regardless of efficiency here is why 2 transistor 5VSB sucks, this one had the critical cap fail. It killed an Intel 775 motherboard

Is that an Antec power supply?

[Pentium4]

Re: Found a brand new Comp USA PSU

Absolutely it is It needs your 5VSB mod!!!

[everell]

Re: Found a brand new Comp USA PSU

Absolutely it is It needs your 5VSB mod!!!

So...................did you put the 5vsb mod on your Antec?

[Pentium4]

Re: Found a brand new Comp USA PSU

Not yet! I just got it that day

[larrymoencurly]

Re: Found a brand new Comp USA PSU

Yes, This design looks particularly old. The 5vsb transistor not being attached to the heatsink is a good indicator that this was originally an AT design that was adapted to ATX.

I had an ATX that may have originally been an AT design because its 5Vsb was on a separate circuit board. PC Power & Cooling featured it in a magazine ad to show how bad a PSU could be.

Here's a Leadman identical to Pentium4's CompUSA unit, right down to the April 13, 2001 production date, only the +3.3V has a choke in its output, and the heatsinks are different.

[ben7]

Re: Found a brand new Comp USA PSU

I had an ATX that may have originally been an AT design because its 5Vsb was on a separate circuit board. PC Power & Cooling featured it in a magazine ad to show how bad a PSU could be.

Here's a Leadman identical to Pentium4's CompUSA unit, right down to the April 13, 2001 production date, only the +3.3V has a choke in its output, and the heatsinks are different.

Those are actually nice heatsinks ... big rectifier diodes, probably 1N540x type? The transformer isn't one of those really tiny ones, and there is proper EMI filtering ... only bad thing is the caps .. rulycon on the output? :P

[tom66]

Re: Found a brand new Comp USA PSU

If they are present… It clearly has *some* impact if the THD is such problem, right?

I'm not sure what your point is, yeah you may have some energy past a few kHz but it's pretty much insignificant.

And 5VSB circuits using killer caps do suck big time. But they don't have to, it is possible to make them more reliable, but my point is you may as well use a controller IC because it'll end up cheaper by the time you've made all the modifications.

[everell]

Re: Found a brand new Comp USA PSU

T... only bad thing is the caps .. rulycon on the output? :P

Can't be Rulycon,,,,,,,,,,,they aren't bloated. Every Rulycon on my CompUSA psu was bloated!

[ben7]

Re: Found a brand new Comp USA PSU

Can't be Rulycon,,,,,,,,,,,they aren't bloated. Every Rulycon on my CompUSA psu was bloated!

Oh JEE, you're right!

[Pentium4]

Re: Found a brand new Comp USA PSU

Oh JEE, you're right!

I had an ATX that may have originally been an AT design because its 5Vsb was on a separate circuit board. PC Power & Cooling featured it in a magazine ad to show how bad a PSU could be.

Here's a Leadman identical to Pentium4's CompUSA unit, right down to the April 13, 2001 production date, only the +3.3V has a choke in its output, and the heatsinks are different.

And at least yours has a little heat sink on the 5VSB transistor

[larrymoencurly]

Re: Found a brand new Comp USA PSU

Those are actually nice heatsinks ... big rectifier diodes, probably 1N540x type? The transformer isn't one of those really tiny ones, and there is proper EMI filtering ... only bad thing is the caps .. rulycon on the output? :P

1N5404 diodes and all JEE brand capacitors, most of them swollen. The transformer is the same size as those in 300W Antec SmartPowers.

I had an even older Leadman PSU with Leadman brand capacitors in it.

And at least yours has a little heat sink on the 5VSB transistor

I added that because every other ATX power supply I saw had that transistor mounted on a heatsink.

Back in the olden days, CompUSA got its brand of PSUs from many suppliers, including Win-Tact (used by PC Power & Cooling), but there was no way to tell from the cardboard box, and CompUSA wouldn't let us open it unless we paid the 15% restocking fee.

[Behemot]

Re: Found a brand new Comp USA PSU

I'm not sure what your point is, yeah you may have some energy past a few kHz but it's pretty much insignificant.

And 5VSB circuits using killer caps do suck big time. But they don't have to, it is possible to make them more reliable, but my point is you may as well use a controller IC because it'll end up cheaper by the time you've made all the modifications.

I guess you have no idea what you are talking about. I have first-hand experience with this matter you see. Power supply without PFC made my otherwise relatively precise wattmeter measure with 50 % error. Yeat PSUs with at least passive PFC are just fine.

So come again, what some energy on higher harmonics? And once again, if you were true and this was just some marginal problem, why all that hystery about PFC in EU? I tell you why: it is not marginal, it results in actual problems, for example motors can be badly damaged by heavily distorted power.

[tom66]

Re: Found a brand new Comp USA PSU

Motors can't be damaged by other devices' poor power factor, that doesn't make sense. A motor has a fixed power factor which is determined by its design and construction, some times have higher PF and some have lower PF. Often, in an industrial system you'll add a power factor correction circuit, consisting of inductors and capacitors, or you'll use a VFD with built in APFC.

Why the concern over PFC? Because it costs electricity suppliers more money to have poor PF loads (which they can't charge extra for)... and they lobbied/appealed to the EU to change this so they could continue using the existing infrastructure which will need upgrading, but they can delay it or roll it out slower than if everyone kept using bridge rectifiers + big caps.

MOST of the energy (>98%) is within the first few kHz.

Your meter is crap if it cannot measure the power usage of devices accurately if they have poor PF. You should consider upgrading it. My £10 eBay device works well.