I'm trying to modify this psu (Diamond 500w)

[forza764]

Hi, my father gave me this psu as a gift and after opening it, i found that is missing some filtering coils in the input and output. I have some coils and caps from dead psus to put in, but i can't because there is a resistor blocking the space for the input coil and one of the pi coils that should be in the secondary.

My question is ¿is ok to remove the resistors and put the coils in?

The psu has about 6 months of light use, and it still works, i just wanna improve it for learning and maybe use it as a backup.

[etnietering]

Re: I'm trying to modify this psu (Diamond 500w)

For the input side, the power supply will still work fine without this resistor. It's just a bleeder resistor to drain the EMI filter caps when the PSU is unplugged. Without it, if the AC is unplugged at the peak of the wave, these caps could sit with ~140 (or 280) volts on them, which would hurt if you touched them. It would be best to see if you can get the filter coil to fit in over the top of it, but if not then it should be fine to remove the resistor.

For the output side, you should be able to just stick the coil in anyways, over the top of the resistor. From the picture, it looks like the resistor isn't covering the holes for the coil. If the coil isn't sitting flush to the PCB that's not a problem. If you really want to remove it though, you'll need to check what it's connected to. If it's just a simple load resistor from 3.3v to ground, then it's probably OK to remove (but the voltage might not be stable at very little or no load). However, if it's connected to something else it's important and should not be removed.

Other than that - make sure you install the bridge rectifier properly (+ to + and - to -), and make sure to watch the voltages on the output caps. Also, be sure the coils in the input filter match the silkscreen on the PCB, otherwise you will end up with at best a blown fuse. Good luck! Be sure to post more pictures when you're done.

[stj]

Re: I'm trying to modify this psu (Diamond 500w)

put the resistor on the other side of the board.

[370forlife]

Re: I'm trying to modify this psu (Diamond 500w)

If you want some more work and have some solder wick or a good solder sucker, you can replace the secondary side rectifiers. I circled them in the picture I attached, as well as the missing 3.3v choke. What psu's did you get these parts out of? You can try taking the rectifiers off those too and use them to beef this one up. I usually beef up the secondary rectifiers so that if anything blows it will be the primary switchers, and if they blow they almost always won't take the attached hardware.

[forza764]

Re: I'm trying to modify this psu (Diamond 500w)

Ok, i soldered the bridge rectifier, the input coil, x cap, and the pi coils. The caps haven't been replaced because i want to test it first, maybe tommorrow.

Some of the parts came from a dead ISO psu, the primary was shorted, lots of burned traces, and now its missing a lots of components, hehe.

For the secondary i have two MBR3045, but the holes spacing is too small for those rectifiers, any ideas?

[370forlife]

Re: I'm trying to modify this psu (Diamond 500w)

MBR3045's are, simply enough, 30A, 45V schottky's (voltage acts the same like on a cap, operates up to that voltage). The 5v rectifier currently installed is probably the same thing. Sounds like they are the same package as the current 5v, a to-247 package or maybe a to-3p. Either way, there is 2 things you can do. Carefully bend the legs in to fit the holes (I've done this before with success,) or you can order some to-220 higher amperage schottky's, which would be more expensive (I would just ship you some of mine, but shipping would be a problem...)

If you have more X caps you can salvage, put another directly on the AC receptacle, as 1 .1uf is not really enough. A higher value one like a .33uf or .47uf would do better. Replace the .1uf with a higher value one too if you have one that would fit.

[forza764]

Re: I'm trying to modify this psu (Diamond 500w)

I have another question, after installing the bridge rectifier, ¿the mains selector switch is unaffected in function? here in Vzla the mains is 115v.

[gramph]

Re: I'm trying to modify this psu (Diamond 500w)

umm dont replace the 3.3v rectifier because it's actually not a rectifier but it's a mosfet. It takes power from 5v and regulates it to 3.3v.

You can only replace with another similar mosfet.

[370forlife]

Re: I'm trying to modify this psu (Diamond 500w)

gramph-

I was afraid of this. Couldn't get a clear reading of the part number, but I believe you are right, this would account for the absence of the 3.3v choke as the mosfet cleans up the 5v into 3.3v and it creates a lot less ripple. Also the absence of the Mag-Amp coil near the primary transformer. Typically this indicates a very cheap adaptation of a AT psu to a ATX psu.

Forza764, can you please post the part number on the 3.3v rectifier, I have seen many cheap designs that use even a 40A mosfet here which would not need replacing.

As for the voltage selector switch, it still needs it. If you removed it, the psu would be stuck in 230V. If you short the two wires, it will be stuck in 115v. The only time they don't need a voltage selector switch is if they are Active PFC (Passive PFC still requires it,) or they have a special little daughter board with a circuit that detects and automatically changes the voltage setting. (though the only psu I have seen with that is my 450W ATNG)

[forza764]

Re: I'm trying to modify this psu (Diamond 500w)

The part for the 3.3v is CET CEP3120

For the 5v i think is a S30140C, not sure, hard to read.

For the 12v is a Mospec F16C20C.

[370forlife]

Re: I'm trying to modify this psu (Diamond 500w)



Yep, its a 30V, 40A mosfet, so no need to replace. IIRC, this is not only a cheaper way of doing it, but also more efficient.

Bad news, 12V rectifier is only a 16A, 20V schottky. Try and replace it with one of the 30A, 45V's you salvaged out of the other psu's.

The 5v rectifier is a 30A, 40V part. If you really wanted to over do it, the 5v is typically silkscreened for two schottky's. You could try and put those two identical MBR3045's in there, and replace the 12v's with the 5v's old schottky. Problem is two to-247's are very thick, the original screw for the 5v is probably not long enough to go through both.

BTW, you have some pretty good soldering.

[forza764]

Re: I'm trying to modify this psu (Diamond 500w)

Secondary ready, and installed.

I will test it tomorrow, if it works ok, im gonna recap and change to a bigger case that comes with a on/off switch, the original doesn't have a switch and the 5vsb is always on, thing that i dont like.

[stj]

Re: I'm trying to modify this psu (Diamond 500w)

add an led for the 5v standby - that's always nice.
a 330 or 470 ohm resistor will be good for driving an led from 5v.

[POM_MJ]

Re: I'm trying to modify this psu (Diamond 500w)

>> Bad news, 12V rectifier is only a 16A, 20V schottky. Try and replace it with one of the 30A, 45V's you salvaged out of the other psu's.

12V recitifier F16C20 is 16A 200V Fast Recovery type, not Schottky.
if you replace it with xxA 45V Schottky diode, it might be short immediately after powered ON because of breakdown by higher reverse voltage.
you might need to replace with xxA 60V Schottky diode.

[370forlife]

Re: I'm trying to modify this psu (Diamond 500w)

It should be fine. I have replaced many of the 200V Fast recovery type's in these cheap design psu's with 45V-60V, should be fine.

[forza764]

Re: I'm trying to modify this psu (Diamond 500w)

Bad news.

I tested it and the +5vsb reads 5.0 volts, but when i try to start it, the only thing it does is a tick sound and nothing happens.

I used for load an old cd-rom drive.

[POM_MJ]

Re: I'm trying to modify this psu (Diamond 500w)

change 12V rectifier as I said.

[stj]

Re: I'm trying to modify this psu (Diamond 500w)

tick = safety-shutdown because of a short or overload.

[forza764]

Re: I'm trying to modify this psu (Diamond 500w)

Ok i removed the MBR3045 and reinstalled the Mospec F16C20C, but the psu still doesn't want to turn on, i checked for shorts and i can't find any.

Any suggestions?

[POM_MJ]

Re: I'm trying to modify this psu (Diamond 500w)

restore all original rectifier parts, if the PSU still doesn't turn ON, problem might happened with main transistor switcher.