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About PC power supply units

2017-11-21 10:26:00,  In: Electronics, Curiosities, Other

Recently I acquired a few power supply units for PCs and I decided to share some knowledge about their quality. Because these units were defective I had to open them, fix if possible, and re-solder wires as they were from some e-junk wjere copper is valuable. Testing was simple: Load the power supply unit with an old, damaged IDE hard disk, turn it on, check voltages (they should not be well OK, as one old hard disk is not enough to keep regulated line), then load the unit on 5V line with 12V/21W light bulb and check regulation then. Most passed these tests after capacitor repairs.

   Tagan TG380-U01

Let's see the first example: The Tagan TG380-U01. Tagan is known as manufacturer of a good, high-end power supply units, and it looks like they made them really well. The unit is packed with technology, they put large heatsinks and thermal regulator on a separate, small board. Because packing is tight, two fans are pumping air through the unit.

Here is an example how the good power supply unit should look like. This is a really good hardware and I was a bit hesitating to just give it a typical "tail" of wires. The only fault was input AC capacitor in standby converter, which i slocated on a separate board.

   Chieftec

Chieftecs are good-quality power supply units, known from their reliability. I found the problems with 2 units in secondary capacitors. After replacing them voltages became well enough.

These units are frequently chosen for home and office PCs by people who were using Codegen-like power supply units and it ended bad. Chieftecs usually have no material savings which may result in hardware being damaged.
A bit newer unit, APS-450S is shown below.

This unit has also some components missing, it looks like they had a separate regulator for negative voltage. Unfortunately for some reason servicing this unit is very hard as the soldering alloy doesn't want to melt using typical soldering iron! I had to use a high-power iron used to solder sheets of metal to melt it. Even more, the soldering connections look like a "dry joint" is everywhere - they are not, this alloy just looks like it's going to fall apart, but it doesn't, it's very hard. I think that they could be some experiments with lead-free alloys.

   Delta

In a budget, mass-produced PC market Delta power supply units were popular. We can see that some components are missing. The input coil filter has been moved to the casing (not shown here) so it's shorted.

This is not a top-quality power supply unit, but totally enough. Unfortunately shorting 12V to -5V totally killed the output regulator chip, so it haven't survived.

   Modecom MC350 and FEEL

Modecom started as a local PC power supply brand which used good Fortron-like units under the model MC, like MC-350. These power supply units were good and a bit cheaper than Chieftec. Let's see inside:

We can see components missing - -5V line is absent in this model, and these are for -5V line.

I don't know was Modecom FEEL another company's product or another line, but these power units were really poor. They have been made to be cheapest possible, and their output overpower protection is... partial. Generally it may not survive a short. Inside, we can see that some components are just not installed, they are shorted or omitted. In the photo below I removed a defective fuse and one filtering capacitor - other things were just not present.

This made many people think that all Modecoms are bad units - No! Modecom FEEL are bad units! These MC are good units similar to much more expensive Fortrons.

   Codegen

The bad legend of PC power supply units. And... earlier ones are generally usable with some precautions. It is only important to clearly separate which Codegens are good and which should be avoided. What I found, many Codegens, especially AT, which are "made in Czech republic" are not bad. The technology is cheap and quality is not the highest, but they are still good and usable. Protection circuits are scarce, but they are in place. As the time was going on, Codegens became cheaper and cheaper. Around 2004 most thermal protection circuits disappeared from them. Codegens made around 2004-2005 had very high early failure rate in bathtub curve, but after most broken, the remaining are relatively solid. Only clean them every few years, because, to be honest, there is NO thermal protection as known in other power supplies!
Later Codegens are a big no-go. To manufacture cheaper, they decided to remove more protection components. It means that failures could, and many times did, catastrophic voltages on the PC destroying electronics. Sudden explosion of HV capacitor could cause voltage spike on ground instead of blown fuse (proximity of grounded heatsink with NO electrical insulation!). Additionally, there is some information over the Internet that Codegens and "TakeMe"s had... fake PFCs!
This is the "Better" Codegen. It is rated 350W, but I think 250 is quite maximum.

About "worse" Codegens, I don't have them. If I see that inside there are no output coils, but their places are shorted, I don't use such unit.

Power supply unit is an essential part of a PC. And although similar in design, the manufacturing of these devices is different. Because one flaw in power unit may destroy many PC components, it is important to choose a good, solid unit and take care of it properly.


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