PSU: Cheap AND Heavy = Good????

In the world of audio amplifiers, receivers, and power amps, WEIGHT is the single most important spec. If it weighs a ton, it is a fine piece.

PSUs, I suspect, are no exception. (however, I wouldn't put it past manufacturers to add meaningless weight to give the impression of quality.)

At any rate, reviews of the name brands, in my book, establish the standard.

If you look at PSUs, they are all basically generic with a label differentiating them. I'll bet for every 20 brands (countless no names) there is a single manufacturer - it might even be more like 50 brands.)

I was at a local computer show last weekend and there was a 500 watt PSU that was no name (to me at least) and it was HEAVY and $35. I was tempted to buy it but I didn't - guess I didn't feel like gambling. (There were some 500 watt PSUs that honestly felt like there was nothing inside the sheet metal case!!!!!).

Now let me make a comment: Quality welders had weights approaching 1000 lbs. Until Inverter Technology came along. The same quality welder could now weigh 100 lbs. The same thing happened with Carver audio amplifiers. His 400 watt 7" cube violated all the rules. Since PSUs do not have a big transformer in them, I guess they are basically inverter designs. So we are comparing the weight of inverters which I guess is still legitimate.

What would be of great value would be the weights of the many no name PSUs that are out there. When you look inside a $200 name brand, it is clear that they are definitely cashing in on their name. Taiwan makes electronics for the cost of dirt. PSUs don't even have bone fide transformers in them nor big power transistors so how much can the manufacturing cost be????

I'm sure there are heavy, cheap PSUs out there because the OTHER attribute of Taiwan is COPYING!! All you have to do is show up at a manufacturer and say, "I want you to make these." (as you hand them an Antec.) They could probably make it for $8 on a bad day.

I guess this is a rant, huh?
Sorry!
Tom

To see if weight really matters, I did a little experiment.

I have two disassembled dead power supplies here, one a trash brand 250W, and one a decent brand 350W. Fortunately for the test, I can't be sure which is which, because I threw out the metal covers long ago, so it's truly a blind comparison. I had previously removed the two largest capacitors for a project, but I found them and, judging by brown gunk left behind, I matched them with 90% certainty to the boards they came from.

Both power supplies are switching power supplies, as evidenced by the small transformer and IC part numbers. They both weigh around the same ballpark. If one does weigh more than the other, it is the second board that weighs more.

Board 1: http://mattsmac.ath.cx/images/ps1.jpg

This one has the standard layout of transformers. The heatsinks are aluminum plates bent over at the top, with checkerboard teeth. Thermal pads are used between the power components and the heatsinks. It has four toroids; one is wrapped using plastic-insulated wire rather than magnet wire, and one appears to be wrapped as a transformer. This one died from an overheated (on fire) 1/2 watt resistor near the bottom of the picture. The high voltage capacitors are 470uF, and slightly taller than the other supply's. There are four 2200uF low-voltage capacitors, and three or four chokes.


Board 2: http://mattsmac.ath.cx/images/ps2.jpg

This one has an identical layout of transformers and high-voltage capacitors. The heatsinks are larger, with multiple fins above the components. Thermal pads are used here as well. The 120v bridge rectifier has been removed, but was in the same place as the other board (below the capacitors). The two high-voltage capacitors were slightly shorter than the other supply's, and were 330uF each. There are two toroids, both wrapped with magnet wire. There is a large choke with large-gauge magnet wire. There are five 1000uF low-voltage capacitors among several other smaller ones. I see five chokes. This board is somewhat heavier than the other, but it's not too noticeable.


Actually, in looking at the boards, I found distinguishing marks on one to identify it. These are blurred out in the photo. Can you guess which is which? It's the PSU challenge, like the Pepsi challenge!

what company was the PSU?

Taiwan's been a lot better than that for a long time, and those Antecs are designed and made by a Taiwanese company, Channel Well Technology.

I thought that PSUs had to contain a real transformer or else they'd be boxes of death. But some are smaller than other, and when I looked inside a 400W or larger MGE at Fry's, my first thought was, "where's the transformer"?

Well, not much activity on this thread, so I thought I'd reveal which power supply is which. The first one I linked and described is a 250W Deer. The second is a 350W PSU, a better brand IIRC, and may have been an Antec. As I noted, the weight difference between them was hardly noticeable. It's likely that in this type of power supply, the heaviest parts would be the heatsinks and the outer casing. Heatsinks only help up to a point; the switching MOSFETs attached to them have current limits even with great cooling. Obviously the only advantage to a thicker casing is physical sturdiness. Given all this, I'd say that, unless the power supply you saw was of radically different design, it's not necessarily better than a lighter unit.

I'm confused (as usual). If the 250W Deer is inferior, why does it have 470uF high voltage capacitors while the 350W PSU has only 330uF capacitors? And can either PSU really be that good when each one has plain capacitors connected between each line and ground (small brown things in lower right corner of each picture) instead of UL-rated ones?

Neither look too great to me... that Deer is identical to mine, except the resistor didn't quite catch fire and my output filter caps all fried. The 470uf capacitors on the primary side in these are utter garbage - tried to use them to repair a TV set and they ended up being worse than the 25 year old ones they were replacing.

MrCreosote said:

In the world of audio amplifiers, receivers, and power amps, WEIGHT is the single most important spec. If it weighs a ton, it is a fine piece.

Click to expand...

If that were true Sony could build monsterous amps, fill them with lead to increade their weight, and really good amps... not quite true.

But general, a light flimsy PSU is not the best, as a heavier one, will have more dudads and a bigger heatsink to kill it cool.

But general, a light flimsy PSU is not the best, as a heavier one, will have more dudads and a bigger heatsink to kill it cool.

Click to expand...

And generally a heavier PSU does have a higher quality build, whether that quality is in the casing, heatsinks, or whatever. Certainly not a huge determining factor, but worth noting.

It reminds me of that part in Jurassic Park where the boy picks up these night vision goggles, and the lawyer guy was like "Is it heavy?" "yea" "put it down" or something like that.