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Old 02-28-2022, 10:08 PM   #3163
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Default FSP Group Inc. AX400-PN cap diagram, partial recap, & resistor mods

As far as recapping this PSU goes, it’s very simple. Each main rail has just 2 caps, as shown above (except for the -12V rail.) The only difficult part is getting to those caps due to the tan glue and also due to how cramped the secondary side is. (Those output wires really do get in the way!) But in any case, here is the cap diagram… or rather 2 of them, due to the wires blocking view for some of the caps.
FPS Group Inc. AX400-PN - cap diagram (1).jpg

FPS Group Inc. AX400-PN - cap diagram (2).jpg

Note that I didn’t mark the two 5VSB caps on there, just because of how the images came out. But I think those should be pretty easy to figure out, as there are only 2x 10V, 1000 uF caps in this PSU, and they are right next to the two smaller transformers.

As usual, I was short on capacitors, so I just replaced the “first” cap in each rail (that is, “cap #1” in the diagram above), except the 12V rail, since it had both of its caps failed. I also replaced a lot of the smaller caps that are of importance – namely, the 5VSB start/run cap, the BJT drive circuit caps, and the auxiliary secondary side rail. Here are how the results turned out:
FPS Group Inc. AX400-PN - recapped (1).jpg

FPS Group Inc. AX400-PN - recapped (2).jpg

FPS Group Inc. AX400-PN - recapped (3).jpg

For the 5VSB rail cap #1:
1x Teapo SC, 10V, 1000 uF ---> 1x United Chemicon KZE, 10V, 1000 uF

For the 3.3V rail cap #1:
1x Teapo SEK, 10V, 3300 uF(?) ---> 1x United Chemicon KYB, 6.3V, 3300 uF

For the 5V rail cap #1:
1x Teapo SC, 10V, 3300 uF ---> 1x United Chemicon KYB, 6.3V, 3300 uF

For the 12V rail caps:
2x Teapo SC, 16V, 2200 uF ---> 2x United Chemicon KYB, 16V, 2200 uF

For the -12V rail cap:
1x OST RLP, 16V, 220 uF ---> 1x Rubycon YXJ, 25V, 220 uF

For the 5VSB startup/run cap:
1x Teapo SEK, 50V, 22 uF ---> 1x Nichicon PW, 50V, 22 uF

For the 2x BJT drive circuit caps:
2x Teapo SC 50V, 2.2 uF ---> 2x Panasonic FC, 50V, 2.2 uF

For the auxiliary secondary side cap:
1x Teapo SEK, 50V, 47 uF ---> 1x Nichicon PM, 50V, 47 uF

I also swapped out/around some of the minimum load resistors on the outputs.

3.3V rail minimum load resistor mod:
1x 10 Ohm, 2 Watt ---> 1x 100 Ohm, 0.5 Watt

5V rail minimum load resistor mod:
1x 15 Ohm, 3 Watt ---> 1x 15 Ohm, 3 Watt in series with 1x 10 Ohm, 2 Watt (taken from 3.3V rail)… so total is 25 Ohms, which corresponds to about 1 Watt of power dissipation split between a 3-Watt and a 2-Watt resistor. Needless to say, they both run much cooler now, so this PSU no longer has any hot-running minimum load resistors.

And that’s all for the recapping and modifications I did on this PSU. As mentioned, I’ve had it running this way in my primary “gaming rig” for the last 3 years or so now. When I did the recent check-up, cleaning, and fan lube job a few days ago, all the old Teapo and OST caps I had left from the first time still appeared good. I didn’t pull them to check them, but I didn’t have a reason to either – the PC is still running happy.

Originally Posted by PeteS in CA View Post
Looking at your pix, I was tempted to post, "Where's the beef?!" But for a 250W rating, that actually isn't awful. As long as the input lytics are at least 330uF, it could do 200W reasonably OK-ish.
They are 470 uF, actually... according to the label, anyways. Being JEE brand, who knows. Usually the cheap HV caps regularly show 1 notch lower... but not always.
In any case, I probably won't ever push that PSU past 100W, so even those JEE caps should be good.

Last edited by momaka; 02-28-2022 at 10:15 PM..
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