V2 shutting off

[VAXHeadroom]

All,
I have had my new V2 running for 2 weeks and have almost 8 days of printing time, working great, printing really terrific stuff.
Yesterday it started shutting off while heating up. It will all turn back on when I cycle the on/off switch.

I'm pretty sure this is a power supply problem.

Voltage with Rambo unhooked: 12.5V
Voltage with Rambo running: 12.3V
Voltage with heated bed heating (no extruder): 11.4V
Voltage with both bed and Extruder heating: 11.3V

Seems to be thermally related. The more times I try to get it to run, the sooner it turns off.

I'm using this for production work, not just hobby stuff, any help appreciated.

[geneb]

Try taking the side panels off. That will increase airflow to the interior and will help cool the power supply.

g.

[VAXHeadroom]

Try taking the side panels off. That will increase airflow to the interior and will help cool the power supply.

g.

I'll try it, but are the power supplies really that marginal or is mine damaged?

[VAXHeadroom]

Try taking the side panels off. That will increase airflow to the interior and will help cool the power supply.
g.

I'll try it, but are the power supplies really that marginal or is mine damaged?

I was able to get it to work by both taking off the side panel and back plastic and by heating the bed first until it reaches temperature then starting the print. The print appears to act as something of an insulator and the bed stays hot with very little power (infrequent cycling of the LED in the bed). The air coming out of the power supply out the back is cool.
Just running the pre-heat PLA preset in the printer causes it to shut off before reaching temperature.
But it didn't require this prior to yesterday so something has changed...
How much power is required? 40-50A at 12V? 2 20A + 5A something like that? I may have that much bench supply sitting around... (goes off to rummage in the attic some more)
Thanks for the suggestion, got me going again anyway

[VAXHeadroom]

Try taking the side panels off. That will increase airflow to the interior and will help cool the power supply.
g.

I'll try it, but are the power supplies really that marginal or is mine damaged?

I was able to get it to work by both taking off the side panel and back plastic and by heating the bed first until it reaches temperature then starting the print. The print appears to act as something of an insulator and the bed stays hot with very little power (infrequent cycling of the LED in the bed). The air coming out of the power supply out the back is cool.
Just running the pre-heat PLA preset in the printer causes it to shut off before reaching temperature.
But it didn't require this prior to yesterday so something has changed...
How much power is required? 40-50A at 12V? 2 20A + 5A something like that? I may have that much bench supply sitting around... (goes off to rummage in the attic some more)
Thanks for the suggestion, got me going again anyway

Still a problem, got it going for 1 print, but it was a trial to get it up to temperature.
Opening a support ticket...

[Jrjones]

Mine is at 11.4-11.5 with the heated bed and the hot end on. I do have a 5W (or 10W) resistor across a 5V lead inside the powersupply though, it seems to be more consistent with the resistor.

I am still going to replace the power supply though, since at 11.4V instead of a steady 12V there is about ~10% less power going to the heaters.

A 50A supply isn't needed.
At 12V the heated bed should draw 10.91A or 130.9W (going by the cold resistance of 1.1 ohm)
I replaced the hot end resistors with a 40W cartridge, so 3.33A

And the power the stepper motors take are about 2A each max (from the firmware/rambo wiki) so 8A or 96W

To power the board itself uses 5V switch mode chip capable of 1.5A so 7.5W.
The fans are about 1-2A draw so ~24W worst case

So the powersupply that would run everything would need to be capable of sustaining 300W, or 25A at 12V. For some wriggle room there are plenty of 360W powersupplies on ebay for about $25-$30.

[VAXHeadroom]

Mine is at 11.4-11.5 with the heated bed and the hot end on. I do have a 5W (or 10W) resistor across a 5V lead inside the powersupply though, it seems to be more consistent with the resistor.

I am still going to replace the power supply though, since at 11.4V instead of a steady 12V there is about ~10% less power going to the heaters.

A 50A supply isn't needed.
At 12V the heated bed should draw 10.91A or 130.9W (going by the cold resistance of 1.1 ohm)
I replaced the hot end resistors with a 40W cartridge, so 3.33A

And the power the stepper motors take are about 2A each max (from the firmware/rambo wiki) so 8A or 96W

To power the board itself uses 5V switch mode chip capable of 1.5A so 7.5W.
The fans are about 1-2A draw so ~24W worst case

So the powersupply that would run everything would need to be capable of sustaining 300W, or 25A at 12V. For some wriggle room there are plenty of 360W powersupplies on ebay for about $25-$30.

Excellent info, thank you very much! I looked at both the 30A and the 50A supplies.
Talked to one of the electrical engineers at work today, he asked what voltage the system can run at. I think the limiting factor is the motor drivers. Higher voltage would make the system work much better. The RAMBo board doc says it can take up to 35V, but I doubt the stepper drivers can take that... (have to go look up the parts)... ahh... parts list on the RAMbo reprap wiki - 12-24 volts...
So why in the heck would SeeMeCNC ship this kit with a PC power supply that's marginal when a 30A supply is only $22.50 in 10 quantity from ebay?!? The supply I got with the kit has to be more than that...maybe because the 120V wiring has to be done by hand on the 30A supply whereas the PC supply is UL listed and plugs in (that would be sufficient answer in my book!).

*goes off to rummage in the attic to see what lab supplies I have in a milk crate I'm sure I didn't throw away yet*

[Eric]

If you decide to go with a higher voltage, that's fine, just think it through. The Rambo has its own 5V regulator. The motor drivers are fine too, they're current limiting devices by nature. But the heater and fan connectors output the input voltage. Do the math to figure out how much current the heater elements will draw at higher voltages (I = E/R). The nano fuse can be changed to 10A if needed, but above that you need another solution. 12V Fans may need in-line resistors to avoid a quick death.

[VAXHeadroom]

If you decide to go with a higher voltage, that's fine, just think it through. The Rambo has its own 5V regulator. The motor drivers are fine too, they're current limiting devices by nature. But the heater and fan connectors output the input voltage. Do the math to figure out how much current the heater elements will draw at higher voltages (I = E/R). The nano fuse can be changed to 10A if needed, but above that you need another solution. 12V Fans may need in-line resistors to avoid a quick death.

Very good point. I was really just musing about the higher voltages. I didn't buy this to hack on it, I really just need to run it 24/7 for the next month, and right now I'm dead in the water. I can make >$30/day with it running, nothing with it stopped.

[Holy1]

I had to replace my power supply pretty much right away . Put in a 750w and it has worked well since. I understand them keeping the price point below $1000 but the stock p/s is marginal at best.

[VAXHeadroom]

I had to replace my power supply pretty much right away . Put in a 750w and it has worked well since. I understand them keeping the price point below $1000 but the stock p/s is marginal at best.

Looks like mine will be replaced under warranty...

[Holy1]

I had to replace my power supply pretty much right away . Put in a 750w and it has worked well since. I understand them keeping the price point below $1000 but the stock p/s is marginal at best.

Looks like mine will be replaced under warranty...

That's good. They did nothing for me.

[VAXHeadroom]

New power supply received today, installed, recalibrated heights and off to the races My V2 is running perfectly again!!
Much thanks to Matterhackers and SeeMeCNC support!

[VAXHeadroom]

While installing my replacement power supply I had a revelation - the hole in the bottom should be where the PS fan pulls air in.
But you can't mount it that way - if you turn the power supply over so it pulls cool air in from underneath the printer, the 120V AC input socket is behind the Z axis stepper motor.
Looks to me like they used to use a different power supply where the AC input was in a different place, but they didn't make the change.
Now it pulls air in from inside the bottom chassis which is heated by the hot plate.
Ideally you would have to change the PS mounting plate and the orientation of the Z axis motor, mount the power supply with the fan on the bottom, then reverse the Z motor polarity (turn the plug around or patch the software) to get the current power supply to pull air in from the bottom.

My alternative is to leave all 3 back panels (2 hard, 1 plastic cover) off so cool air is pulled into the power supply and it doesn't overheat.

I have a spare 12v fan floating around, so maybe I'll make a panel to mount it and use it to force cool air into the bottom chassis.