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PC Power Supply Discussion Troubleshooting and discussion of computer power supplies

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  #21  
Old 06-18-2013
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Originally Posted by walterm View Post
Japanese capacitors are "the" choice. Taiwanese can be good, passable, or forget it.
Chinese (with exceptions?) are meh to terrible.
BadCaps website is a good source of information, if fanatic at times.

Generally you want to have decent soldering equipment and skills before attempting changing caps. AND caps retaining charge are dangerous.
Yes you can remove switch and jumper for 110v. the trouble is (unlikely in usa) someone would use a cord with a 220 wall plug to power psu. But they could do that with the switch set to the wrong voltage.
The psu socket is universal I think.
Having enough electrical knowledge to have replaced the caps on several motherboards and an arcade game monitor, I am well aware of what dangers caps present and would never treat them lightly.

Having cleaned out the Bestec PSU, it does seem to be operating a little better... it was still hot out in my workshop and the power supply didn't shut down, so I think the dust was acting as an insulator, making the heat "stick" inside the PSU and causing it to shut down.

If I were to try to upgrade EVERY electrolytic capacitor inside the PSU, even the tiny ones, to high quality Japanese brand (just for the fun of it), what is/are the most likely improvement(s) that would be made to the PSU's performance? Would it even be really worth it? Could you sell the PSU as a more reliable unit? Just curious...

Making things "better" than they were, originally, is always fun for me.
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  #22  
Old 06-19-2013
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Improved ripple & noise performance, and better hold-up times. And you'll have to worry less about a cap blowing in the future.

But the fact remains that this Bestec's +5VSB rail has a fatal design flaw, that by its very nature causes overvoltage that will kill motherboards. Period. You can't change that with a few component substitutions.
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  #23  
Old 06-19-2013
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Originally Posted by Phaedrus2129 View Post
Improved ripple & noise performance, and better hold-up times. And you'll have to worry less about a cap blowing in the future.

But the fact remains that this Bestec's +5VSB rail has a fatal design flaw, that by its very nature causes overvoltage that will kill motherboards. Period. You can't change that with a few component substitutions.
Is this flaw still present in the 12Z revision (which I have)? What was improved between 12E and 12Z... that's a lot of letters difference... it's gotta mean something! How many revisions did they make between the 12E and 12Z? You saying the 5Vsb issue was NEVER addressed? That's insane! What does the 5Vsb actually do? Could you wire in a voltage regulator circuit to that, to "fix" it? Just wondering.

Maybe it's just best to go out and the poor thing?

By the way... is Bestec even still around? I can't find them in Google... just old 250w/300w units on various sites.
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  #24  
Old 06-19-2013
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Oh, you have the 12Z? Then that's a totally different PSU. I think they fixed the issue in that one, yeah.


Still, it's not worth much even with new caps. It's a mediocre low-end OEM unit. A few millivolts less ripple won't change that.
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  #25  
Old 06-20-2013
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The 12E's 5vsb circuit is just a bog standard 2 transistor circuit found in most low end units. There is a 50v, 47uf cap that when it goes bad, it causes the 5vsb to become a 25+vsb. Using a high quality japanese replacement capacitor in this position will fix the problem.

There is a member on Badcaps who has done extensive and well documented mods on the bestec models.

Here is his mods done to the 12Z.

Here is his thread of his modifications to the 12E, including completely removing the 2 transistor 5vsb circuit and replacing it with one controlled by an IC.

And Here is his mod to raise the 5vsb output to 5A with a 12E.
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