oops, can it be fixed?

Hey just looking for some advice or help.
recently bought and constructed a prusa i3 from geeetech. build was crazy frustrating but made it through and got the printer honed in to making decent prints. Only problem was that for some reason my heat bed wasnt working. changed the connection of my heatbed to extruder port just to test the bed itself and it heated so nothing wrong with the bed itself as far as i could tell. figured i would take my voltmeter to the connections to see if i could narrow down the issue when i accidentally touched the two tines for the extruder heater port. i know i shorted something as there was spark and now my psu will not turn on. i can still get readings from the thermesters on the computer so i know that my board isnt pooched, but is there a fuse or resistor on the psu i can replace or flip to get my power running again? or should i start shopping for a new psu?

If it's one of the cheapo switching supplies, there's usually a fuse inside that you can replace, probably soldered down. Use only the exact same type fuse which is usually marked in the metal at one or both ends of the fuse.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

hey thanks for such a quick reply =] found the fuse and desoldered ok, upon full inspection though the fuse seems fine, fillament is still intact. as far as i can tell there is no secondary either. gonna replace it anyways in the name of due diligence but if it is not the cause any other suggestions?

Make sure you test the supply while it is disconnected from the controller board. It's possible you blew the MOSFET on the controller board. They tend to die shorted, so if you're testing this with the supply connected to the controller it might continue to misbehave.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

so changed the fuse, it was 5amp 250v, psu works, reading 12v output dc at com and v+ terminals, still no power to the motors or extruder but the thermistor is still reading on my computer. there are two very small fuses on the board reading 10 amp and 15 amp. no clue what to call them for a product search. gonna try to get some pics up tonight to display them maybe they might be the issue?

A 5 amp power supply is too small for a heatbed. You need at least 15 and more likly a 20 amp. PS. If you are talking a but the yellow ( I'm assuming there yellow) fuses. They are poly fuses and are self resetting, unless you've really damaged them. I would check the mosfets and to use the heatbed you will need to get a bigger power supply.

I think it was the *INPUT* fuse that was 5A - IE good for 600 watts . . . they typically don't fuse the output . . .

Thermistors, endstops and the like do not use 12 volts, and will read even the 12v supply is unplugged.

- Tim

Edited 3 time(s). Last edit at 08/02/2015 10:03PM by tadawson.

Thanks Tim..read that a little fast I guess..

Check the polyfuse on the RAMPs board. Check for 12v on the OUTPUT of the PSU AND on the inputs to the RAMPs board at 5A and 11A. This verifies you have no break in the wires between PSU and RAMPs. The 5Amp connection powers motors and other ancillary items. the 11Amp connection powers the heatbed alone. Both these connections have a poly fuse (slim flat brown component next to the main power connector)

Thermistor readings, endstop status etc will all work via USB connection irrespective of whether the PSU is on or not.

Check the voltage OUTPUT on D8 with PSU connected and heatbed switched ON to see if your getting heatbed output.

See this link for further reference (if you havent done so already) [www.reprap.org]

HTH

Edited 1 time(s). Last edit at 08/02/2015 11:21PM by Mutley3D.

thanks for all the info, good call on the wires between psu and board, didnt take that into account. one of the wires definitely has a break in it, gonna replace and work my way from there.

fixed wire, one of my polyfuses is not reading though, looking into replacing it