Ultra Xfinity 600w 5vsb mod

[mockingbird]

Re: Ultra Xfinity 600w 5vsb mod

short of a hacksaw, I doubt it... they are more or less enclosed, and due to the shape of the heatsinks and the sixe of the transformers (the heatsinks cover parts of the transformers), gettign in there without sawing heatsinks will require desoldering.

nof if the traces hadn't lifted (punched through, that is, due to a soldring defect), it would be no big deal. however, since one of the anchor traces is an island, it may come off with the solder if I am not careful... hence the issue.

I struggled with two small caps on an SP450 in a similar tight spot... Anyone who's re-capped the SP450 knows what I'm referring to...

Actually it was a lot easier to desolder the two little Fuhjjyu caps than I imagined. Locate the pads for the two caps underneath and mark it. Heat both the pads at the same time (This is easy with 5 x 11 caps, just add solder to bridge both leads so that when you heat one, both of them become molten) and while it's molten, it only requires very slight pulling pressure from the right side up of the PCB to get the cap out of there. It may even fall out on it's own.

Now when both caps are out, use wick to clear the holes... Now, it's a lot easier than you think. When you get the replacement caps with the long leads, you leave the leads on, and the leads are in effect your "tweezers". Manoeuver them in there. You don't need tweezers.

[ratdude747]

Re: Ultra Xfinity 600w 5vsb mod

I struggled with two small caps on an SP450 in a similar tight spot... Anyone who's re-capped the SP450 knows what I'm referring to...

Actually it was a lot easier to desolder the two little Fuhjjyu caps than I imagined. Locate the pads for the two caps underneath and mark it. Heat both the pads at the same time (This is easy with 5 x 11 caps, just add solder to bridge both leads so that when you heat one, both of them become molten) and while it's molten, it only requires very slight pulling pressure from the right side up of the PCB to get the cap out of there. It may even fall out on it's own.

Now when both caps are out, use wick to clear the holes... Now, it's a lot easier than you think. When you get the replacement caps with the long leads, you leave the leads on, and the leads are in effect your "tweezers". Manoeuver them in there. You don't need tweezers.

I removed the primary heatsink and then used the quoted method to reove the caps, as they were a tight fit.

i was also able to super glue the lifted traces back to the board.

FYI, it uses 2 10uf 50v caps. added to order. had to use nichicon PW since that value doesn't exist in nichicon HE.

[c_hegge]

Re: Ultra Xfinity 600w 5vsb mod

I believe those two caps are the start caps for the switching transistors. I when recapping Antec StupidPowers, I usually use de-soldering braid on the legs and they just fall out. The replacments can be a bit hard to get in, but it's perfectly doable when the legs are long enough.

[ratdude747]

Re: Ultra Xfinity 600w 5vsb mod

I believe those two caps are the start caps for the switching transistors. I when recapping Antec StupidPowers, I usually use de-soldering braid on the legs and they just fall out. The replacments can be a bit hard to get in, but it's perfectly doable when the legs are long enough.

with the primary heatsink out, it is easy... I won't reinstall it until after i have those spots re-filled with caps (good ones)... for now, the heatsink and attached goodies are sittign on the shelf next to the rest of the PCB.

my question is regarding using nichicon pw for those 2 start up caps. Will those be ok? they are 105 C rated...

[shovenose]

Re: Ultra Xfinity 600w 5vsb mod

Quick question: how do I desolder the doodads on psu heatsinks? There are too many legs to heat all at once...

[brethin]

Re: Ultra Xfinity 600w 5vsb mod

Quick question: how do I desolder the doodads on psu heatsinks? There are too many legs to heat all at once...

You heat and suck each doodad then it will freeup and come out for you.

[shovenose]

Re: Ultra Xfinity 600w 5vsb mod

Suck? So I need a solder sucker?

[c_hegge]

Re: Ultra Xfinity 600w 5vsb mod

^either that or desoldering braid (which is what I use).

@ratdude. Nichicon PW will be fine. I use their Panny equivilant, FC for startup caps and it's fine.

[ratdude747]

Re: Ultra Xfinity 600w 5vsb mod

ok, tonight I will place the order.

I am correct that I should replace the tiny 1/2W 100 ohm load resistor with a 1W equivlant? (I included it in the order). I am also wondering if there is a way to place a heat sink on the resistor?

[mockingbird]

Re: Ultra Xfinity 600w 5vsb mod

with the primary heatsink out, it is easy... I won't reinstall it until after i have those spots re-filled with caps (good ones)... for now, the heatsink and attached goodies are sittign on the shelf next to the rest of the PCB.

my question is regarding using nichicon pw for those 2 start up caps. Will those be ok? they are 105 C rated...

Always replace small GP caps in PSUs with Nichicon PW...

Witht the small values, PW class caps serve essentially as a heat-tolerant, highly reliable cap.

[c_hegge]

Re: Ultra Xfinity 600w 5vsb mod

I am correct that I should replace the tiny 1/2W 100 ohm load resistor with a 1W equivlant? (I included it in the order). I am also wondering if there is a way to place a heat sink on the resistor?

Yes. If you can find a heat sink that won't interfere with anything else, then you can use some thermal epoxy to attach it to the resistor (although be careful not to get it on the legs as it is conductive). Another thing I have done before is solder it onto some wires and attach it to the secondary heat sink with thermal epoxy.

[ratdude747]

Re: Ultra Xfinity 600w 5vsb mod

order placed.

hope this all works out...

[mockingbird]

Re: Ultra Xfinity 600w 5vsb mod

Where did you order from?

[ratdude747]

Re: Ultra Xfinity 600w 5vsb mod

mouser.

(technically, not ordered yet, but will be very soon).

[mockingbird]

Re: Ultra Xfinity 600w 5vsb mod

Yea, I'm going with Newark this time around because I need some other stuff that only they have. I'm also about to order very soon, probably tomorrow.

[ratdude747]

Re: Ultra Xfinity 600w 5vsb mod

parts ordered.

[Rulycat]

Re: Ultra Xfinity 600w 5vsb mod

parts ordered.

Great. Let us know how you get on with it.

[momaka]

Re: Ultra Xfinity 600w 5vsb mod

I believe those two caps are the start caps for the switching transistors.

Not exactly.
This is a half-bridge design - PWM controller is on the secondary side, not the primary, so there are no start-up capacitors for the main PSU section.

What these caps do is they filter the pulses from the driving transformer that turn on the BJTs. They aren't exactly super-critical or anything, so technically they don't *need* to be replaced, but it's a good idea since if the old ones are going bad, the efficiency of the PSU will also become worse. And worse efficiency = more heat inside the PSU.

As for the 100 Ohm resistor, the 1/2W rating wouldn't have been so bad if it was a little further from the 5vsb filter caps. But because it isn't, a 1W resistor would be better since it is bigger and will run cooler. You don't need any heatsinks or anything like that. A 100 Ohm resistor on the 5vsb is only dissipating V*V/R or (5*5)/100 = 0.25 watts, which is not that much at all. It's only half of what your current resistor is rated for.

Which reminds me... check if there are any large loading resistors on the 3.3v, 5v, and 12v rails.

[ratdude747]

Re: Ultra Xfinity 600w 5vsb mod

Not exactly.
This is a half-bridge design - PWM controller is on the secondary side, not the primary, so there are no start-up capacitors for the main PSU section.

What these caps do is they filter the pulses from the driving transformer that turn on the BJTs. They aren't exactly super-critical or anything, so technically they don't *need* to be replaced, but it's a good idea since if the old ones are going bad, the efficiency of the PSU will also become worse. And worse efficiency = more heat inside the PSU.

As for the 100 Ohm resistor, the 1/2W rating wouldn't have been so bad if it was a little further from the 5vsb filter caps. But because it isn't, a 1W resistor would be better since it is bigger and will run cooler. You don't need any heatsinks or anything like that. A 100 Ohm resistor on the 5vsb is only dissipating V*V/R or (5*5)/100 = 0.25 watts, which is not that much at all. It's only half of what your current resistor is rated for.

Which reminds me... check if there are any large loading resistors on the 3.3v, 5v, and 12v rails.

uhh the order is already on it's way to my house... all i grabbed was a 1W 100 ohm resistor...

I am less concerned about the other rails, as this PSU is a twin fan setup and those railsare only active when the fan is on... unlike the 5vsb, those rails always are being activly cooled when activated.

[momaka]

Re: Ultra Xfinity 600w 5vsb mod

uhh the order is already on it's way to my house... all i grabbed was a 1W 100 ohm resistor...

That's fine. Just check what they are anyways. Some are just better off removed completely rather than replaced. Older Deer and Allied PSUs, for example, like to put 100 Ohm 2W resistors on the 12v rail - that's 1.44W of heat, which is quite considerable (enough to darken the PCB board and cook caps). I remove those on sight and just replace them with whatever I find in my junk box - usually 2x 1000 Ohm 1/2W in parallel.