Power Supply only works when not connected to Rambo

[GeekStreetSolutions]

My Rostock Max v2 is behaving weirdly. Here is what happened:

I went to turn on my printer and upon flipping the power switch, the lcd and the green led right next to the usb port on the rambo blinked for less than a second.

I assumed this meant my power supply was dead, and I bought a new one.

After cutting the wires (and voiding the warranty) and connecting them to the plug on the Rambo and flipping the switch nothing happened. Not even the lcd or the green led blinked. After randomly playing around with the original power supply I noticed that if I shorted the green and black wires when it was not hooked up to the rambo it would start spinning the fan. However as soon as I hooked it back up to the rambo it went back to only blinking the lcd and led (also the fan spun for a split second.

Is this a short? My fuses are all fine, and I don't know what to test for next.

[nitewatchman]

I think that you definitely have a short and the P/S is shutting down immediatelly and restoring when the short is removed. Look for wire whiskers on the connectors.

nitewatchman

[GeekStreetSolutions]

I have rewired the power supply connector and the result is the same as before. Could a short on any wire cause the power supply to shut off or just the wires directly connected to it?

[Polygonhell]

Pretty much any short will cause the PSU to turn off! but most of them will also blow a fuse on the RAMBO.
Assuming you bought a random ATX PSU to replace the one SeeMeCNC shipped, you should know that not all ATX PSU's will work unless you have a load on the 5V line, and the usual symptom is they shut off when you try and draw current from the 12 V line

If you're trying to track down a short it's a lot safer to do it with a meter, than to rewire and check.

[GeekStreetSolutions]

Here is the power supply I bought: http://www.frys.com/product/6740055

It won't power on but I want to make sure it can be fixed with a load on the 5v line before I go and buy another power supply. Is there any power supplies on frys website that are known to work?

[Polygonhell]

Turn off the power from the board and put a meter across the power terminals, look at the resistance, if it's really low you have a short, and you NEED to track that down before doing anything else.
With nothing running the board should pull MUCH less than 4A so V=IR etc. you should see more than 3Ohms of resistance, probably a lot more, anything less than that and there is an issue.

You can verify the CPU has the 5V issue by attaching a CDROM drive or similar to a spare connector to see if it starts working, there is no way to tell from the specs page of an ATX PSU if it will work reliably without a load on the 5V line. People who've used alternate supplies can probably point to ones that are known to work.

[nitewatchman]

Is there any power supplies on drys website that are known to work?

I am using this one.

http://www.frys.com/product/7856689?sit ... IN_RSLT_PG

A load on the 5VDC rail is not necessary for full output and when running a Rev 2 Heated Bed and a Hot End with a 40watt Cartridge there is no voltage sag between loaded and idle. Additionally, I have never heard the fan come on. If the fan has run it has been at such low speed that I can not hear it.

I would certainly buy this again.

nitewatchman

[GeekStreetSolutions]

After some further testing I was able to power the 3D printer using an 350w power supply, and all wires plugged in except the heated bed thermistor.
Assuming I had found the issue I unscrewed the heated bed and measured the resistance of the thermistor. To my surprise, the thermistor was fine. Next I put the multimeter probes at the very end of the thermistor wiring to test for faulty wires, but again the thermistor was fine. In the meantime I bought a replacement thermistor (has not arrived yet), and two of these power supplies: http://www.frys.com/product/6740055 (I think I shorted the first one I bought) and have not been able to get them running while plugged into the Rambo, only when unplugged. Is it fine to use the 350w power supply, until I figure out the problems with the ones I just bought? Also any ideas on the thermistor issue?

[GeekStreetSolutions]

So my second power supply in a week got fried, I am able to exchange it for another, and I may get this one: http://www.frys.com/product/7947110

The protection circuits on this would mean If I short the wiring, I would just have to restart the power supply and I am up and running or will die like the others? Also, does anybody have any info on the results stated in the post above?