Thursday, March 3, 2016

The bad capacitor saga continues! Recapping the FSP Hexa HE-500

Last week I got this older computer PSU from the local flea market to replace another one which was retired. Luckily, the old one went out without taking any other components with it, so all that was needed to have a fully working computer was to get a decent PSU.

The "new" PSU is a Fortron (FSP) Hexa HE-500 model. I thought that it would be a good idea to go with FSP since it's a well-known brand, respected by many people, and one of the biggest OEMs in the world. I've had laptop chargers made by them that worked almost daily since ~2006 without any problems at all.

But things seem to have changed and the build quality suffered quite a bit in the last years. As expected the Hexa was full of dust so before mounting it I decided to clean it up a bit. Vacuuming didn't work too well so the unit needed to be opened and brushed clean. Upon taking the screws off and cleaning most of the dust off, I was greeted by this:

CapXon capacitors...

Yes, a nightmarish cocktail of CapXon, OST and Teapo capacitors. CapXons are really bad quality (I have replaced many of them inside LCD monitors). TEAPOs are on the mediocre side now especially because they don't take heat too well. Too bad, since they had some good series in the late 90's.

The lower voltage CapXons tend to bulge and leak while the high voltage ones exhibit some sort of internal corrosion that eats away the internal wires that go to the snap-in connectors. This is really bad since it leaves the current unfiltered and it can make the the active PFC circuit to go up in smoke.

There is a post on the badcaps forum that explains this issue in depth:
http://www.badcaps.net/forum/showthread.php?t=8168

Another thing that has been hypothesised is that bad main capacitors make the active PFC coil burst up in flames. This is one of the problems that plagued many FSP models (like the Bluestorm II) - there are many posts on tech forums about it.

To fix all these potential issues, I decided to replace all the capacitors inside the unit with something better. The only high quality caps available here were Nichicon and Panasonic so I went with a mix of those. Before starting work I drew a capacitor map to know the location and type of each and every one of them. You can see it below (sorry for the bad drawing :P):

FSP Hexa HE-500 capacitor map

Then I made a table which contains all the information about the old capacitors. The specifications were extracted from the datasheets released by CapXon / Teapo / OST. Luckily, they were easy to find. In case you have a similar unit, you can use this table to choose capacitors with similar characteristics. Word of advice: make sure to also look at the size, see why below :P.

FSP HE-500 complete electrolytic capacitor list

The first to be replaced was the high voltage cap from the primary. Can you spot the difference? The original Capxon had 270 uF and a 420 volts @ 85 °C rating, a bit on the edge for an active PFC design. The replacement Nichicon fairs much better, with 390 uF and 450 volts @ 105 °C rating. One odd thing is that although the CapXon had smaller capacitance, voltage and temperature rating, the datasheet listed a ripple current rating 25% better than the Nichicon. Yeah right CapXon...


Quite the difference between the two.





The good thing is that there was enough space to fit the beast between the heatsinks. The bad thing is that  it required moving the small PWM control isolation transformer on a separate daughterboard which I bolted to the heatsink that also holds the switching transistors:

Making way for the capacitor. A resistor, a transformer and a coil had to be relocated.
The daughterboard that now holds the PWM isolator transformer

The daughterboard connected to the mainboard using a ribbon cable
It all turned out well in the end, nothing was mounted in reverse and the voltages are in spec.

Everything put back to where it belongs

After working on this unit I can safely throw out a mini-review:

Pluses:

  • Made by a well known company
  • Nice looking, black metal case
  • Pretty silent
  • Delivers the power as advertised
  • Good cross-loading performance for a group regulated design
  • Good build quality for such a low price

Minuses:

  • Horrendous choice of capacitors
  • Bad material for the PCB: it warped because of the heat, the traces lifted even after using a soldering iron with temperature control
  • No insulation under the PCB, combined with the warping it can lead to disaster
  • The heatsink from the secondary gets quite hot, maybe better diodes would have fixed that (it uses 2 x SBR30A60CT)
  • The Yate Loon fan used a low quality lubricant that seems to be acidic: it eroded the sleeve bearing and became something that looks like a rust-colored, semi-solid wax
  • The distance between the SATA / Molex connectors is too small, I needed a Molex to SATA adapter to connect both the HDD and DVD writer.


Would I get one again? Probably, if the price was right. But in all honesty after having to replace each capacitor, I'd rather save up some money and get a more expensive model, maybe another FSP - but Japanese capacitors are a must.

Thanks for reading!

2 comments:

  1. hi, very good blog. recently racap my FSP hexa 500w with japan capacitor,

    I used power cap Nichicon 270uf 450v, not moving any transformer. I use some hard wire to solder.

    on output stage, I replace all capxon with equivalent low esr Panasonic capacitor.

    so far so good.

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    Replies
    1. Good work, this will ensure a long life for the PSU. Too bad I didn't find a smaller power capacitor at the time. Anyway, there is already 1 year since the recap, and the PSU still works great. These Panasonic caps are really good, too bad they're not used more often.

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