PSU mod: Seeking advice

[natto fire]

I am rewiring a PSU for a project that needs very short and fewer wires. It is basically going to be the bare PSU next to the motherboard, attached with standoffs to the motherboard tray.

I wanted to wire this the right way, which I was assuming involved desolerding all the original connections, cut to length, and then resolder what I needed, possibly eliminating a connector or two from the PCB. The only connections I am going to need are the 24pin ATX, 4pin 12v, 8 pin PCI-e, 1 SATA, and 1 12v line for the fans, 37 wires total (running the PS_ON directly to a switch). Ordinarily, I prefer to desolder with braid, but there is a significant amount of solder on these joints, so I am assuming I should use a sucker?

I tested a bit of braid out on a junk PSU (Antec 460w, project one is Antec 380w dual rail) and it seemed like it was taking a lot of heat to get flow, had me worried about nearby components. I am not a soldering noob, but desoldering this much on electronics is definitely a first, looking for any tips, or "don't worry they're tougher than you think" type comments .

Another thing I am worried about is EMF. I know that in the "old style" cases the PSU was really close to the motherboard, but it is also in a separate case and perpendicular to it. My project is going to have the PSU a fraction of an inch from the motherboard, on the same plane. Should I be concerned with EMF and find a way to shield it?

Any advice appreciated. Here is a pic of mock up that gives you an idea of how close they will be.

 

[BoomerD]

You may get good answers here, but I think Jonnyguru.com would be your best source of information.

 

[pcgeek11]

I would use a sucker. Damn that is close. I would worry about that transformer that close to the RAM. I would try and fasten a small shield between them.

 

[natto fire]

I would use a sucker. Damn that is close. I would worry about that transformer that close to the RAM. I would try and fasten a small shield between them.

Yeah, the RAM is what worried me as well, although I could omit the two closest sticks if I have to. Of course I lost my solder sucker in my last move, hate rebuying even small tools like that, but not as much as I like using the right tool for a job. Speaking of that, I remember gauss meters being a lot more expensive, although it seems like they are marketing some of them towards the ghost hunting crowd. 60 dollar Lutron that gets decent enough reviews

While I do want this to be a tidy build, it is not critical as the components will not be visible. I might do some testing at full load to see what happens, I can't see it causing any kind of permanent damage. A blue screen from having the PSU too close to the RAM almost sounds comical, in the testing phase at least.

 

[RaiderJ]

An easy way to test memory errors would just be to run memtest on the machine for a couple days.

Total guess on my part - but I wouldn't think the PSU proximity would be a problem. Motherboard components, RAM included, should be able to handle the EMF from the PSU no problem.

 

[MrTeal]

I've done a lot of soldering, and if I were you I would just use a good iron directly on the pads/wires until the solder flows, then pull out the wires. Worry about removing the solder after the wires are gone, it will be a breeze either with a sucker or braid. Just remember to keep your tip tinned. Either way though, it's a single sided board so it should be pretty easy no matter how you do it, and you're much less like to lift a trace than if you had a multi-layer board.

 

[natto fire]

An easy way to test memory errors would just be to run memtest on the machine for a couple days.

Total guess on my part - but I wouldn't think the PSU proximity would be a problem. Motherboard components, RAM included, should be able to handle the EMF from the PSU no problem.

Will the Memtest load up the CPU too though? Ideally I want the PSU running full tilt when I do the test. I am going to be using integrated video at first to test how much heat I am dealing with. This hopefully will make it into a wood case as soon as I either get better at cutting dovetails, or cave and use a router for box joints. Either way, I think thermals are going to be a pretty tight. Volume is 770 ci, was going to try to cool it with 3 120mm fans.

Unfortunately I only have an AM3 board lying around. These days my "lying around" pile is mere scraps, anyone want a 6800GT AGP, Prescott Celeron?

Oh, I am going to go out on a limb here and guess that the dual rails cannot be combined so I could just have one connection to potentially draw 32 amps from? I couldn't help but notice that the dual rail PSU has two smaller sets, and two large transistors (MOSFETS?) attached to the heatsinks compared to 4 large ones on my "donor" which appears to be constructed 98% similar otherwise. Anyhow, I'm assuming it would damage the smaller ones if it tried to pull the full 32 amp current through one of them, but I don't know transistors all that well.

I've done a lot of soldering, and if I were you I would just use a good iron directly on the pads/wires until the solder flows, then pull out the wires. Worry about removing the solder after the wires are gone, it will be a breeze either with a sucker or braid. Just remember to keep your tip tinned. Either way though, it's a single sided board so it should be pretty easy no matter how you do it, and you're much less like to lift a trace than if you had a multi-layer board.

I tried to do that at first, I am using a gun instead of an iron, but there really is a ridiculous amount of solder on them, and hard to keep it all flowing at the same time, especially the grounds, which is basically a continuous 1/4" high 1" long bead of solder.

Thanks everyone for the help so far!

 

[MrTeal]

I tried to do that at first, I am using a gun instead of an iron, but there really is a ridiculous amount of solder on them, and hard to keep it all flowing at the same time, especially the grounds, which is basically a continuous 1/4" high 1" long bead of solder.

Thanks everyone for the help so far!

I'm surprised you are having that much trouble, especially with a gun. Are you sure your gun is working correctly? Clamp it on its side, and heat up one wire at a time until it's lose, and then remove it with your other hand, then move on to the next one.

 

[natto fire]

I'm surprised you are having that much trouble, especially with a gun. Are you sure your gun is working correctly? Clamp it on its side, and heat up one wire at a time until it's lose, and then remove it with your other hand, then move on to the next one.

I must not have mentioned that the wires are tied together in a clip to form one joint, with some clips carrying 5 wires.

Pic of a 3.3v line I managed to get out, with only 3 wires.

I just got back from getting a solder sucker, which is actually called a vacuum desoldering tool, good tip to know if you go to a store looking for one. The guys at the hardware store said it sounded like a neat tool after I explained how it operated, but they didn't stock them. First Radioshack was out of them, second Radioshack (a scant 3 miles away) had one, $15, which was a bit more than I expected. It seems pretty well made though, has an aluminum barrel where my old one was plastic. Probably more cosmetic than anything though, heh.

 

[MrTeal]

Ah, that makes more sense. If you want to remove them easier then, either cut the crimp terminal or cut all the wires just above the crimp terminal. That will prevent the wires acting as a large heatsink and will make removing them much easier.

 

[VirtualLarry]

For testing, Prime95 Blend test really stresses the RAM.

 

[BoomerD]

If you really want to stress test your RAM and CPU...

http://www.techspot.com/downloads/4965-intelburntest.html

It will also test your CPU cooling solution...make sure you carefully monitor temps.

 

[natto fire]

If you really want to stress test your RAM and CPU...

http://www.techspot.com/downloads/4965-intelburntest.html

It will also test your CPU cooling solution...make sure you carefully monitor temps.

Thanks, but unfortunately this project is built from scrap parts, and I am stuck with AMD. If this design proves to handle a decent amount of heat, I will buy better Intel stuff, and maybe even a video card. Unless there is a way to run that program on AMD?

Thanks for the tip about cutting the wires MrTeal. I initially wanted to save the crimped connectors for reuse because they look tidy, and I can't seem to find new ones locally. Are they essentially there as stress relief for the individual wires, or for an electrical reason, and would I be able to omit them when resoldering?

 

[BoomerD]

unfortunately, Intel(R) designed the binaries in a way that makes it not run at all on any AMD CPUs

Apparently not for AMD. Looks like you're going to have to use the "standard" programs. OCCT should do a good job along with Prime95.