power supply shuts off when heating hotend

Everything I try and heat up my hotend, my PSU shuts off. I checked the wires and there are no shorts. It's an authentic J head so I'm 99% sure it's not the hotend.

Any one had this happen?

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greghoge.com

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Has it worked before?
What power is PSU?
Check resistance of hotend. 1% is enough chance. Try connecting it straight to the PSU. See if that trips it.
Try switching RAMPS with no load or a low load like a bulb. If it still trips it could be faulty board.
-a

Hello gmh,

I have had a similar problem with a PSU (assuming you are using a PC PSU).

I turns out a PC PSU, especially the cheaper ones, are designed to mainly regulate on the 5V line. Not the 12V. So if you are only loading the 12V and have nothing on the 5V the voltage can go too low and it cuts on undervoltage.

So - Are you using a PC PSU?

What is the amperage capacity of the PSU? Could you be overloading it?

It's a PC PSU I've been using in my Printrbot JR for almost 2 years now. works great there without having the 5V rail loaded. It outputs around 11.5V.

I'll check the resistance of the hotend and double check for shorts when I get home tonight.

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greghoge.com

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The voltage isn't the important number - what is the amperage or wattage capacity. If you've been operating the PSU at close to its capacity for two years, perhaps things have just caught up to you.

The typical 3D printer using RAMPS is fused for about 16 amps total - 5 amps on one rail and 11 on the other. Usually the draw is less that this, but it still needs to be within the PSU specs.

Edited 1 time(s). Last edit at 06/09/2015 03:13PM by jbernardis.

It's a 5A 250W psu. Apparently it doesn't want to turn on at all now....

I have a 12V 30A switching psu that wont turn on either even when plugged back into the printrbot. I have no idea what's going on.

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greghoge.com

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Do they work when not connected?
Disconnect the hotend at the board and try again.
Disconnect everything and reconnect one item at a time (with power off.)

Wiring fault or faulty board maybe.
Have you any wiring 'commoned' ie sharing a feed to hotend and fan?
-a

Quote
gmh39
It's a 5A 250W psu. Apparently it doesn't want to turn on at all now....

I have a 12V 30A switching psu that wont turn on either even when plugged back into the printrbot. I have no idea what's going on.

That seems a little out of spec if you ask me... Take a picture of the label on the side of the PSU and post it here. A PSU is rated as an overall wattage and then has ratings for each rail/voltage if you will. the important one here is the 12v line.

about the PSUs not coming back on. check your connection from the green wire to ground, Switch on the back and the power cable you are using for the PSU (i know its annoying to read these things but often we forget to check)

I had a similar problem with one of my ramps boards. If i had any load on any of the FETS they would short out and the power would go bye bye.

Figured it out. It was the how I had everything wired. I think I had some of the wires mixed up.

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greghoge.com

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