ATX Power Supply Low Voltage

Hey all,
I bought a nice Corsair ATX power supply to power my printer, it is rated for 40+ amps on its single 12V rail so I bought this figuring it would be perfect for my application. I was using a 10A laptop charger (which did work) but it gets REALLY warm when the printer is running.

But I have an issue, I am only getting about 11.8V coming out of the power supply and as a result my print bed is struggling to get to 90C, it takes almost an hour and will not get over 91C. By comparrison the laptop charger was putting out 12.7V and that heated up the bed in about 30 min right to 95C.

Any suggestions as to how I can improve the 12V voltage output? Has anyone seen a similar issue?
I have seen a few people who have recommended adding a ~10W power resistor to the 5V rail. But I'm not an expert and fail to understand how modifying the 5V line can improve the volatge output on the 12V line. Currently I dont have anything hooked up to any of the 5V or 3.3V lines.

Thanks!

I'm not sure this is really a power supply issue. The difference in voltages is probably only giving you about 15% less power

There are a lot of postings about heat bed problems.

Most of the problems are normally related to faulty heat beds, wires being too thin, lack of insulation below the heat bed, cold air from open windows etc blowing over the printer and cooling things, thickness of glass causing a lot of thermal mass.

Personally, I have problems getting the bed to 115deg. I've replaced the heat bed with one from a supplier linked from the wiki, but it didn't make much difference.
I put very large wires to the he'd bed, and made them as short as possible, but again it didn't make a big difference.
I put the whole printer in an enclosure I built, and this helped me a bit.

At the moment I put a towel on the bed while its heating up, and that really helps to get it to 115 deg in a reasonable time frame eg 15 mins.

But I've never really got to the bottom of the problem, as my PSU is putting out around 13V.

In the long run I will probable switch to using 24V.

BTW. Do not wire 2 ATX PSUs in series to get 24V. I tried to use this based on postings on Instructables.com, but the person posting had modified the internals of their PSUs and had disconnected the Earths, which I consider to be dangerous.
But the negative rail on the 2 PSUs I have, is connected to Earth, so wiring them in series ends up shorting out one of the PSUs 12V output.

If you have 2 of those laptop style PSUs, you may be able to wire them in series, as the negative output may not be connected to Earth.

Or get a 19v laptop PSU and set the Max PWM settings. ( this is not my idea, I got it from another posting, but it does seem a clever trick )

You paid for a better supply and you got one that is more closely regulated. It's doing what it was designed to do. You *might* get a boost on +12 by loading the +5. I'd hope you don't (it indicates they cut some corners on the supply) I've always liked Corsair supplies for computers.

What you should get is an industrial 12V 29A or 15V 23A supply. They come with an easy way to adjust them so you can get back to your 12.7V supply rail. The 12V unit likely will go up to 13.5 to 14V. The 15V supplies will come down to 13 to 13.5V. As you bump up the voltage on the +12 supply, you will get less current out of it.

Bob,
Thanks for the feedback. Do you have a recommended supplier / manufacturer?

I've always had good luck with MeanWell supplies. The SE-350-12 and SE-350-15 are the two supplies I was looking at as I wrote my last post. TRC Electronics (and *many* others) have them for $44.80. If you get one, get it from a dealer. I've been sold a number of fakes on the auction sites.....

I can't take any credit for TRC, another member remedied them. I've placed several orders with them and they have done well on all of them. They also are about 2 hours down the road so that helps a little with shipping.

[www.trcelectronics.com]

There's nothing magic about MeanWell. Just like the Corsair, they have a lot of competitors, some of them also do a good job.

Bob,
Thanks alot! I have ordered the suggested 12V power supply and will follow up when I receive it and implement it.

- Ryan C.