Heat Bed does not heat  

Re: Heat Bed does not heat

There's an LED on the bed connector. It's visible and should illuminate when the board is sending voltage to heat the bed. Is that coming on?

If it is, but no heat, you could have opened the heating element itself.

If it's not, then you board is not putting voltage to the bed for any of a number of reasons.

Re: Heat Bed does not heat

You say none of the fuses LOOK blown...

this type of fuse can be deceiving... can toy please test the fuses with a multimeter?

Or change the fuses for known good ones?

and try again?

regards Joan

Re: Heat Bed does not heat

Is that coming on?

The LED does not light up.

please test the fuses with a multimeter?

A current seems to go through them fine with a multimeter. I don't have any others on hand to test, but it does not look like the fuses are the problem.

Edit: I should note that the hotend does heat, and I believe the hotend and heat bed share a fuse?

Re: Heat Bed does not heat

Do you have any voltage across the bed power input to the Einsy when the power supply is on? Could be something as simple as a loose connection in the power supply assembly.

EDIT: I should clarify that the the bed and nozzle are on different circuits form the PSU and do not share a fuse. The basic Einsy rambo circuit is here:

https://github.com/ultimachine/Einsy-Rambo/blob/1.1a/board/Project%20Outputs/Schematic%20Prints_Einsy%20Rambo_1.1a.PDF

This is defined for a 12V PSU but I doubt that Prusa Research have made many modifications to the circuit other than a few component swaps to make everything 24V capable.

If you look at the heater outputs curcuit on sheet 7 you will see that X13 ( the nozzle heater output) is driven by 12V2 and the bed is dirven by 12V3. Both these are setup on sheet 2 from seperate inputs and use seperate fuses..

Re: Heat Bed does not heat

Well, an update..

I turned the printer on and measured ~24V across both power inputs on the board. I then ran a pre-heat to check and... the bed heated. However, about 30s later, the printer lost power. Since then, I have not had trouble with the heat bed, but the printer is losing power randomly, and sometimes flickering on and off. It also sometimes refuses to turn back on and I have to leave it for a couple minutes.

Also, while maintaining the bed temp, the PSU audibly clicks in sync with the heat bed turning on and off. I do not recall it doing this in the past, but it easily could have, so I am not sure if this is important.

Re: Heat Bed does not heat

If it's the whole printer and not only the heat bed, then your PSU is dying. Time for a replacement.