R.I.P. Power Supply

[Mjolinor]

I think the 270 ohm may be 0.27 ohms so may be hard to get an accurate reading for depending on your meter.

Are you sure you have the multiplier right. It may be 270 across an inductor so should read zero anyway.

As Printbus says, if there is an over current then it will shut down before you even know it has come on.

[spaceorange12]

Thanks for all of the help everyone has given me. I will try to answer all of your questions
Some specs:
RAMPS 1.4 w/ LCD
12" Heatbed w/ built-in relay
12v 30a power supply (RIP)
14awg wire for power connections (RIP, maybe)
Tests I've done:
Disconnected everything from 30a ps and plugged into power (ps still wouldnt turn on)
Connected old 20a ps to stock RAMPS (ps wouldnt turn on, but worked by itself afterwards)
Connected old RAMPS to old ps using my stock 14awg power wiring (neither would turn on)
Conclusion:
I think that my power wires are bad or broken. I am replacing them with some thicker 12awg wire and testing that now.

[printbus]

What kind of wiring did you use before? If it was some of the highly flexible silicone insulated stuff, one thought is you might overtightened cable ties or something and over time, the insulation was damaged.

[spaceorange12]

It was some stranded wire with standard insulation, bought from home depot. I checked over all the wires, no sign of any damage. Very confused as to what the cause of this is.

[BLKKROW]

I want to include my experience to help the community.

I recently had a power supply that died and I noticed some signs of it dying and wanted to include them here.

It started with an electrical whine whenever I would heat up the heat bed or the hot end by themselves. Once I would heat them together the whine would go away.

After this my power supply output a lot of noise when heating up and being used, kinda like the fan was on overload. Then today I attempted to print and the power supply made so much random noise that it was not bearable to use.

So I ordered another power supply (one of the potential knock offs of the Mean Well) from Amazon today. Thanks to one day shipping I have it installed and the noise difference is incredible!

Just be on the look out everyone, these potential knock offs don't last to long. I had my previous one for a year.

[spaceorange12]

I got a big 40a ps off amazon and have that running now. Everything powers on and functions as normal except for the heated bed. When I try to bring it to temp, it doesn't even get warm and I don't hear the relay "click". I have it wired up the exact same way that I did before this whole mess happened, so the problem isn't the wiring.
Again, thanks for all of the advice and responses from all of you.

[BLKKROW]

I got a big 40a ps off amazon and have that running now. Everything powers on and functions as normal except for the heated bed. When I try to bring it to temp, it doesn't even get warm and I don't hear the relay "click". I have it wired up the exact same way that I did before this whole mess happened, so the problem isn't the wiring.
Again, thanks for all of the advice and responses from all of you.

Have you checked the traces on the relay? Do they look burnt?

[spaceorange12]

Have you checked the traces on the relay? Do they look burnt?

Nope. In fact all connections to the heatbed look just fine. Maybe something on the RAMPS is broken?

[printbus]

If you have the relay coil connected to the RAMPS D8 terminals, make sure you're still supplying 12v to the 11-amp power input on RAMPS. Some people have thought that since their heavy gauge wiring is now going to the relay instead, they don't need to supply power to the RAMPS 11-amp input. That input, however, is still needed in order for RAMPS to output the voltage required to energize the relay.

As a test, you could remove the relay coil wires from RAMPS and apply 12V directly to the relay wires. If that energizes the relay (and the heat bed warms up), you know for sure that there's something wrong the RAMPS hardware or in the firmware.

RAMPS has three outputs (D8, D9, and D10). The normal application has the heat bed connected to D8 and the hot end heater to D10. If D9 isn't being used for a 2nd extruder heater or print cooling fan, you do have the option of moving the relay control to the unused D9 terminal. A few have done this when they've fried the D8 MOSFET on their RAMPS. I think the pin assignment scheme has changed from the older Marlin firmware I'm familiar with, but it still should be a simple change. This swap only works if the relay is used. D9 can't supply the high current for a bed directly. Moving the relay to D9 has another small advantage in that this eliminates the need to supply 12V to the 11-amp input on RAMPS.

[spaceorange12]

i have 12v going to all of the power connections on the ramps
my guess is the d8 mosfet is fried, but i will try the heated bed with my other ramps to make sure