Upgrading the Viotek 450 watt PSU?

[Span24]

Experts,

I will be upgrading the stock 450watt Viotek PSU in my Rostock MAX V2 to a Corsair RM650x Power Unit. The RM650 is fully modular and supplies 12 volts @ 54Amps on a single 12 volt rail. This upgrade has generated a few questions for me:

1) Should I follow GeneBs applicable Rostock instruction manual and designate 4 pairs of black and yellow wires for the heated bed or is something less than 4 pairs sufficient with the upgraded PSU? Say, 2 pairs or even a single pair? I understand the reason for recommending this configuration for the stock PSU but want to know if the upgraded unit would warrant the same configuration...
2) If more than a single pair is required, is it OK to cut, bundle, and crimp them to a 14AWG wire close to the PSU (using a 14 Ga vinyl insulated butt connector) and run that single wire into the Rambo board?
3) To provide additional ventilation and cooling, should I add a 60mm case fan such as that included with the new 29 Amp 'brick' PSU upgrade?

The new PSU is due to arrive on Friday so it looks as though I may have a busy weekend ahead!
Any additional advice would be very much appreciated. Thanks in advance!

Michael

Just so I could practice uploading images, here are some pictures for my education and your entertainment:

[Xenocrates]

So, as a guy who's done similar (with a Corsair CX750 and then a Corsair AX760), your answers are

1: Yes, the advice is based on the ampacity of the original wires, not the design of the old supply.

2: Yes. Again, Ampacity.

3: If it were anything but an RM series, it wouldn't be needed, but the RM series attempt to keep the fan off most of the time, and as such it can cause some issues. Definitely go for a fan.

Additional advice: Make sure you have the proper ATX pinout references. The cables on them are not color coded. Put a load on the 5V rail. It is not a power supply known for exceptional cross-loading characteristics. Rasberry Pi, the Rambo, USB fridge, resistor, pile of LEDs, doesn't matter. Put a load on it that will draw a few amps (two to four, not twenty). Buy a new set of cables for it in case you need to RMA it, and then strip the ones you want to use of everything but the conductors you want. (Chose to use the PCI cables over the Molex or Sata power, as they have more 12V pairs per connector, and are provisioned for more ampacity)

[Span24]

Thanks for the fast reply Xenocrates! All very helpful information!

As I will require a case fan, would it be enough to run the 60mm fan on the 5 volt rail? The LEDs which are already installed are 12 volt and currently run on an external Radio Shack plug-in transformer. I'm hoping to have enough capacity to run them on the Corsair as well.

Thanks again for your expertise!

Michael

[Xenocrates]

You will have more than enough power for the LEDs (The Rambo in total can pull 350W of 12V with the stock fuses). The case fan will likely be enough to make it happy, if the RMx line is as good at cross loading as the RMi line (It's cheaper, but that's mostly in the Corsair link hardware I think). I have an older RM1000, which is much less happy with cross loading as my desktop PSU (The newer lines threw me a little, and I looked it up once I realized that they were new generations). At very least, the 12V rail will be stable. The 5V less so (Which is important to me, as my PT100 amp runs off it, but is unimportant to most printers). You could always power the Rambo off it (It requires soldering up a port, which may not be something you want to do, in addition to changing a jumper).

Best of luck with it (And hopefully it's short enough to fit in and out without gymnastics on the lower access hole. The AX760 isn't, nor is the CX750)

[Span24]

Thanks again Xenocrates!

Any tips on getting the old unit out and the new in? Did you have to disassemble or cut anything? For some reason I thought ATX was ATX and that the dimensions were generally the same... <humph>

Michael

[Xenocrates]

Old out should just drop out as the front edge should be hanging. Pull the wires out first. For getting the new one in, if it doesn't fit in straight, go ahead and wire it in, then start with the front edge of the, after pulling the wires through. Give it a little bit of a shove to get it in. (My 760 which should be a bit longer fit in fine, and the 750 came out okay without opening the bottom) ATX specifies the mounting form factor, the width and height, and the connections, as well as electrical performance, but not the length. In general, higher capacity units are longer. (there would be no hope of getting a AX1200 in there for example).

[Span24]

Thanks again Xenocrates! You're a great resource!

Well, I got the power supply in and began to pull the wires I want to use. My plan is to strip the motherboard connector down leaving only the switch wires remaining then use the four pairs from the CPU cable for the heated bed and two pairs from one PCIE cable for the Rambo and LEDs. When I peeled the bananas I found what looks like some sort of capacitor on each of the cables? (see image) It is connected to one of the 12v wires and one of the common wires. Can someone substantiate this and tell me if they should be removed or (somehow) left in place?

Thanks in advance!

Michael

[Xenocrates]

Those are there for additional ripple suppression, and can be removed, as we don't need our power stable to within 40mV or less. if it's relatively easy to leave them in, I would, as it will keep your power steadier (Only slightly), which will mean slight improvements in handling high temperatures (High load is where ripple suppression usually is needed), and possibly more accurate temperature keeping. However, the system will still function without them.

[Span24]

Well, I thought I should post some updated pictures of the RM650x all wired up and ready to install.

Modular connections...

Wiring (L to R) LEDs, Rambo, Hot-End, PSU Power Switch, Heated Bed

New PSU went in VERY EASILY as the ATX footprint of the RM650x exactly matched that of the failing VioTek.

Got it installed and tested over the weekend! Ill post timings and pictures of the finished unit later in the week.

Thanks to everyone for excellent guidance! Im confident that it saved me some time and heartache!

Michael