Modding Flex ATX PSU

kowabunga_dude

Cable Smoosher
Original poster
Sep 21, 2018
9
1
I am going to be building a PC with a flex atx power supply. I will be shortening the cables and doing custom sleeves regardless of which psu I choose. I also plan to replace the fan if necessary, and am considering an 80mm fan mod. My question is should I go with this FSP 500w 80+ Platinum OR the FSP 500w 80+ gold?

The platinum model does not have a pcie connector, but I read on a forum that I could convert some of the extra connections into a 6+2 pin. My logic is that I want as little of fan noise as possible, so I would in turn opt for the more efficient PSU. Either way 500w is overkill for my build, but I want the extra wattage for possible upgrades down the line, and to be using a lower percentage of available power, again for fan noise.

Also, it was brought to my attention in another thread that the platinum does not have a -12v rail, but I don't know what that means, or how it will negatively affect my build. Can someone explain the differences between these two PSU's and help me decide which one to go with?

I will be running Ryzen 5 2600/x, 2 ssd's (one m.2), 16gb ram, and a 1060 most likely.

Thanks!
 

Enter Plasma

Caliper Novice
Enter Plasma
Sep 24, 2018
22
44
www.enterplasma.com
I see that the platinum one has 2x 8-pin CPU cables. If you are modifying the cables, it's very easy to turn one of those into a 6+2-pin PCIe cable.

It is true that -12v is not listed on the specs of platinum unit. But I see a blue wire in the cables, which usually is the -12v. So it is quite confusing.

I've never tried running a 24-pin without the -12v so I can't really say what would happen, and it's unclear if it is even missing.. I would recommend to contact FSP and double check the compatibility with them, since it doesn't cost anything ;)
 

Elerek

Cable-Tie Ninja
Jul 17, 2017
229
164
I was under the impression that most dc-dc plug in type power supplies like the pico-psu don't supply the -12v and that the vast majority of motherboards now don't use it. I could be wrong though.
 

Gautam

Cable-Tie Ninja
Sep 5, 2016
148
123
There is a lot of detail about this PSU and how to mod it here. (From before the Gold version existed) I'll once again strongly recommend that you make your life significantly easier and get the gold version.
 
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neyurt

Cable-Tie Ninja
Jul 26, 2018
158
163
I agree with @Gautam. Get the gold if you can.

I happened to snatch an openboxed plat version from Amazon for just $67 so I've been messing around with it.

You can use an eps 12 -> 2x pcie 6+2, I'm able to power my gtx 1080 ti mini no problem.

Even worked out a fan mod to get rid of that obnoxious loud fan testing during boot/wake from sleep.

Check here for more info: https://smallformfactor.net/forum/threads/500w-flexatx-psu.52/page-13#post-134256
 

kowabunga_dude

Cable Smoosher
Original poster
Sep 21, 2018
9
1
I agree with @Gautam. Get the gold if you can.

I happened to snatch an openboxed plat version from Amazon for just $67 so I've been messing around with it.

You can use an eps 12 -> 2x pcie 6+2, I'm able to power my gtx 1080 ti mini no problem.

Even worked out a fan mod to get rid of that obnoxious loud fan testing during boot/wake from sleep.

Check here for more info: https://smallformfactor.net/forum/threads/500w-flexatx-psu.52/page-13#post-134256
What was the fan mod that you did? Do you thing its worth the work to change the eps 12 to the pcie 6+2 in order to get that plat efficiency, or do you think the gold will be good enough. My case finally left the Ukraine (custom_mod) so I will actually get to start building in the next month or so!
 

neyurt

Cable-Tie Ninja
Jul 26, 2018
158
163
What was the fan mod that you did? Do you thing its worth the work to change the eps 12 to the pcie 6+2 in order to get that plat efficiency, or do you think the gold will be good enough. My case finally left the Ukraine (custom_mod) so I will actually get to start building in the next month or so!
I linked above to the post where I talked about the mod
 

neyurt

Cable-Tie Ninja
Jul 26, 2018
158
163
Oh I don't know how I missed that haha. Looks great, and thanks for the info about the wiring for the fan!
Np! And I just ordered a enhanced 7660.

The fsp 500 plat is working, but I notice that noctua fan still runs pretty loud in idle ( I'm just sensitive to noise I suppose). I ended up chaining 3 low noise adapters ( 50 ohms each), and itsit's whisper quiet now . My load has been less than 250w though ( gtx 1080 ti & i7-2600k ), so the PSU never even got that hot.

I don't like how if the fan stop running, the PSU would shut off ( I think it's able to detect this bcuz the stock fan is 4-pin pwm) . I'm not sure if this is common behavior with all flex PSU.

The Enhanced uses a 2 wire dc fan, so hopefully it doesn't exhibit the same behavior
 

kowabunga_dude

Cable Smoosher
Original poster
Sep 21, 2018
9
1
Np! And I just ordered a enhanced 7660.

The fsp 500 plat is working, but I notice that noctua fan still runs pretty loud in idle ( I'm just sensitive to noise I suppose). I ended up chaining 3 low noise adapters ( 50 ohms each), and itsit's whisper quiet now . My load has been less than 250w though ( gtx 1080 ti & i7-2600k ), so the PSU never even got that hot.

I don't like how if the fan stop running, the PSU would shut off ( I think it's able to detect this bcuz the stock fan is 4-pin pwm) . I'm not sure if this is common behavior with all flex PSU.

The Enhanced uses a 2 wire dc fan, so hopefully it doesn't exhibit the same behavior
Where did you order the PSU from? How does it compare to the FSP offering? I have never heard of Enhance before...
 

neyurt

Cable-Tie Ninja
Jul 26, 2018
158
163

Gautam

Cable-Tie Ninja
Sep 5, 2016
148
123
Np! And I just ordered a enhanced 7660.

The fsp 500 plat is working, but I notice that noctua fan still runs pretty loud in idle ( I'm just sensitive to noise I suppose). I ended up chaining 3 low noise adapters ( 50 ohms each), and itsit's whisper quiet now . My load has been less than 250w though ( gtx 1080 ti & i7-2600k ), so the PSU never even got that hot.

I don't like how if the fan stop running, the PSU would shut off ( I think it's able to detect this bcuz the stock fan is 4-pin pwm) . I'm not sure if this is common behavior with all flex PSU.

The Enhanced uses a 2 wire dc fan, so hopefully it doesn't exhibit the same behavior
The fan wire mapping is rather concerning, and it’s a good thing you caught it albeit at the cost of a fan. Hopefully this will prevent the same from happening to others.

FWIW the Gold has a 2 pin. And not all of their products have the shutdown behavior as I accidentally ran the 400W for a few hours heavily loaded without a fan.
 
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runcyclexcski

Cable Smoosher
Jan 31, 2019
12
5
I have read this very helpful thread on fan mods of FLEX ATX PSUs, and I am thinking to replace the stock 40mm fan with a much larger, centrifugal fan, rather than top-mount. In your experience, which FLEX ATX PSUs in the 350W+ range is most permissive to modding (solid build, screws rather than rivets, materials, pinouts, etc)? Would you recommend using a 1U server PSU instead?

What I have in mind is to duct a 120 mm (i.e. large diameter, low max RPM) centrifugal blower, mounted next to (rather than on top) of the PSU. This (I hope) would allow me to keep the build within the 40 mm height, while reducing the noise. The geometry of a centrifugal blower (i.e. small diam output) seems adapted well for coupling into the (small-diam) 40 mm input of the original 1U PSU fan. I need to make sure that the PSU controls the new beefier fan as if it was its native one (high RPMs based on load, shut-off if the fan fails etc).

E.g. this blower has 1900 max RPM:

https://www.mouser.co.uk/datasheet/2/471/San_Ace_127BJ32_E-1284333.pdf
 
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neyurt

Cable-Tie Ninja
Jul 26, 2018
158
163
Got my enhanced 7660b today and can confirm it has 2x pcie connectors!

It's working very well. While the stock fan is not loud at all, it does have a whiny sound even at idle (min 3V fan curve). I never went past 300w so I couldn't see how the fan sound would change accordingly starting at 420w.

I think I'm going to replace the stock fan with a noctua a40x20mm or 10mm and have it pwm control with cadance to either the CPU or GPU fan curve.

I'll disconnect the stock DC fan to see if it can run without an fan connected.
 

kowabunga_dude

Cable Smoosher
Original poster
Sep 21, 2018
9
1
Got my enhanced 7660b today and can confirm it has 2x pcie connectors!

It's working very well. While the stock fan is not loud at all, it does have a whiny sound even at idle (min 3V fan curve). I never went past 300w so I couldn't see how the fan sound would change accordingly starting at 420w.

I think I'm going to replace the stock fan with a noctua a40x20mm or 10mm and have it pwm control with cadance to either the CPU or GPU fan curve.

I'll disconnect the stock DC fan to see if it can run without an fan connected.
Did you ever complete the fan mods you mentioned a couple months ago? How did it turn out?
 

VELKASE Michael

Master of Cramming
VELKASE
Oct 7, 2018
495
491
Also consider the 400W FSP Group gold variant. It will still be enough for some future upgrades, but the stock fan spins at a lower RPM compared to the 500W variant out of the box. Power available to you may decrease if the 500W power supply is insufficiently cooled.
 

kowabunga_dude

Cable Smoosher
Original poster
Sep 21, 2018
9
1
Also consider the 400W FSP Group gold variant. It will still be enough for some future upgrades, but the stock fan spins at a lower RPM compared to the 500W variant out of the box. Power available to you may decrease if the 500W power supply is insufficiently cooled.
That's actually the model I ended up going with. I got it for $40 on reddit! Would drilling holes in the top of the PSU case and adding and 80 mm fan be the best way to cool the power supply more? I have a 4.5 case and it's getting a little warm making my GPU fan go crazy due to the heat. It feels like most of the heat is coming from the power supply when I text the case.
 

VELKASE Michael

Master of Cramming
VELKASE
Oct 7, 2018
495
491
That's actually the model I ended up going with. I got it for $40 on reddit! Would drilling holes in the top of the PSU case and adding and 80 mm fan be the best way to cool the power supply more? I have a 4.5 case and it's getting a little warm making my GPU fan go crazy due to the heat. It feels like most of the heat is coming from the power supply when I text the case.
Heat will transfer faster to your hand than to the surrounding air. If you want to get a better qualitative idea of how much heat the power supply dissipates into your case, try taking the PSU out such that it's far away from other powerful components and hold your hand near it without touching the casing. That heat is dissipated through radiation and convection, and there will be very little of it. The rest is exhausted out through the back.

It is unlikely that your power supply is dissipating a lot of heat to your enclosure, unless if its exhaust is being used by other components. Most cases around 4 liters in size orient the PSU such that it exhausts air out of the back. Instead of adding an 80 mm fan to the top or bottom, which might even cause more heat to flow back into the case, I would suggest adding an extra 40 mm fan with a wire grill/ finger guard to the back if you really want to improve airflow.