ATX Issues

Hi all, okay I've been trying to get my printer up and running today, but nothing seems to work. The problem is that every time I turn on the hot end my machine's ATX power supply shuts off, I've tried different power supplies, different heater resistors (of the same kind, mfg. ERX-3SJ6R8), and different Sanguinololus (1.3a, ATX power) , but no matter what I do every time I start the hot end the power supply shuts off instantly. The strange thing is that even this morning it was running just fine, the only thing I did was changed out the heater resistor because it burned out (it's been going for almost a month non-stop). So, basically, my question is this, how do I make it work again?

My machine:
J-head with epcos ntc thermistor and the previously stated resistor
Sanguinololu 1.3a with ATX power terminal
Prusa's PCB heated bed
Marlin
Pronterface

The problem sounds like your hitting the overload protection circuit. Are these both no name ATX PSUs? Ever try just putting a decent load on them? IE 55w car lightbulbs on the 5v and 12v rail? My no name PSU would turn off as soon as I put a 35w bulb on the 12v rail. which isn't really any load at all. And it sounds when you changed the resistor you just walked under the threshold the PSU can handle.

Also I've heard some ATX PSUs don't like having a huge load on the 12v rail with nothing on the 5v, so you could try putting a power resistor or bulb across the 5 volts.

Ah yes, here it is on the wiki: [reprap.org]

Or, L4ZX55 in the past, you could check to make sure that the wires on you hot end aren't in the wrong places in the terminal housing causing your board to short circuit the PSU making it, in turn, shut down whenever you turn the hot end on (just a thought) . Thanks for all the help everyone, but it turns out that this was caused by a simple lack of sleep, and general absent mindedness.

Occasionally, as the resistor goes bad, the wires leading to it may get hot, melt part of the insulator, and short together. If this is the case, then the short will cause your problem. Try measuring the resistance across the resistor at the point where the wires connect to the electronics, and make sure it's in the 5-6 Ohm range.

Out of curiosity, for people who have to artificially load their 5V line, what kind of resistor do you use ? (how many ohms, how hot does it get etc).

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Most of my technical comments should be correct, but is THIS one ?
Anyway, as a rule of thumb, always double check what people write.

I use a 10R 25W AL clad resistor. It only dissipates 2.5W but it still gets too hot to hold without a heatsink.

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[www.hydraraptor.blogspot.com]

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Out of curiosity, for people who have to artificially load their 5V line, what kind of resistor do you use ?

I use an old CD drive. Typically the one coming with the scrap PC I salvaged the PSU from.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Thanks for the replys.
Nice trick with the CD drive motor, Traumflug, you could even stick a fan on it and cool down your electronics instead of just wasting power.

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Most of my technical comments should be correct, but is THIS one ?
Anyway, as a rule of thumb, always double check what people write.

I use a 5R and bolt it to the iiside of the atx case so that the case will disapate the heat from it

I use a really old IDE CD drive.

i had a similar problem with my headted bed when starting out a couple of months back

turned out the ground cable was loose on my electronics and wasnt making enough of a connection and was just dying killing the connected laptop as well (over the US

worth a check on the 12V and GND connections

Got lucky, my power supply doesn't need any load on the 5v to properly give 12V to motors, hotend and heated bed together.

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Most of my technical comments should be correct, but is THIS one ?
Anyway, as a rule of thumb, always double check what people write.