Dual Extruder heating issue.

I'm having an issue with my newly built 3d printer heating both extruders to the proper temperature and keeping them there.

Here is my setup:
ATX 300w power supply.
Dual metal 12v 30w hotends
Ramps 1.4 with marlin firmware.

The left extruder heats pretty quickly and hovers around the 200c mark. The right extruder heats extremely slowly, but it does eventually get there. I can reverse the connection and everything reverses, so I think it's a problem with the ramps board. I have tried a different ramps board and replaced both thermistor/ceramic heaters to make sure that wasn't the issue.

I have marlin setup so D9/D10 are for my extruder. I've checked the voltage before and during the heating process. They are both receiving 12v before I start heating them and once I start heating one pin on each drops to around .5v and the other remains at close to 12v. Once they get to temperature all the pins go back to 12v and you can see it drop again when the temperature goes under 200c.

The issue I have is once I start a dual extruded print, the second extruder drops temp and really doesn't come up to proper temp again. It's always about 5 to 10c below the other, so my prints fail.


How can I remedy this?

Thanks

You're trying to power them both at the same time? You're exceeding the limits of the polyfuse which is only rated at 5 amps. Each hot end will take ~2.5 amps by itself not counting all the other things that need power. Try connecting both hot ends directly to the 12V power supply (not through the ramps board. You still need the - to be connected to the Ramps board to be controlled by the mosfets. This will bypass the fuse so it's not advisable to run it this way all the time, but will work for testing. You can add inline fuses later if it solves the problem.

If it's not advisable to do it this way, how do people power two all metal hotends through a Ramps board?

It's not advisable to drive 200km/h... or eat fried food every day... but people still do it. just sayin'

Well, I've tried hooking up the extruders like you said, but it doesn't help. Still the right extruder doesn't heat properly.

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If it's not advisable to do it this way, how do people power two all metal hotends through a Ramps board?

Probably they use two relais switched by the ramps boards? That would be a safe option and the current through the fuse is almost narda.
Olaf