[Cerrado] Heated Bed Causing System Reboot  

Re: Heated Bed Causing System Reboot

I would see if the problem is related to the PSU by doing the following, but you should verify this test is okay with Prusa support.

- Disconnect everything from the PSU
- Connect the heater bed directly to the PSU and see if the heater bed can hit PLA working temps without the PSU resetting
- Be careful not to leave the connect on too long as to not burn out the heater bed once it hits around 60C

Re: Heated Bed Causing System Reboot

Did you find a solution to this? I ordered an assembled MK2 that arrived via UPS today. Unboxed it and it won't preheat regardless of the material i select to preheat for. Also, self text will not complete; reboots after XYZ end stop check.

Re: Heated Bed Causing System Reboot

No I haven't solved it yet! I contacted support but they still have to get back to me.

Re: Heated Bed Causing System Reboot

I had the same problem. Check that the input voltage setting on the PSU is correct i.e. 110v for USA. This solved the problem for me.

Re: Heated Bed Causing System Reboot

I had the same problem. Check that the input voltage setting on the PSU is correct i.e. 110v for USA. This solved the problem for me.

I saw on the forum this fixed the issue for some people, but mine was already set to 110v for USA.

Thanks for the help though! 😉

Re: Heated Bed Causing System Reboot

I had the same problem. Check that the input voltage setting on the PSU is correct i.e. 110v for USA. This solved the problem for me.

When I received my printer I initially had this issue too. Changing the voltage correctly was the fix for me as well.

Re: Heated Bed Causing System Reboot

I still haven't resolved the heated bed issue where my new printer kit shorts out once a preheat is started or when I try to start a print, and resets/reboots the printer immediately. I've been in contact with support, but they have been unable to resolve the issue for me or get much past the diagnosing stage.

Printer works fine when the bed is unplugged from the board (printer doesn't reboot/short out). To me it seems like a faulty bed, but tech support doesn't seem convinced. Anyone know how to test the bed for proper functionality?

Since the printer operates correctly when the bed is unplugged from the RAMBO, I would deduce that the board is operating properly, but I am very new to the PRUSA printers and am still learning.

I've checked, double checked, and triple checked that the voltage is set correctly and that the board/wiring is hooked up correctly.

Any help you can offer would be great!

Thanks,
Jesse

Re: Heated Bed Causing System Reboot

I cannot believe this issue has been ignored by Prusa Research as you first suggested. They did get back to you later it seems. However I suspect another issue. Measure the resistance across the heated bed disconnected. How many ohms across the terminals and to the metal earthed metal parts? ie the frame? Then reconnect the heated bed without powering up and measure the resistance again, across the heated bed and from the heated bed connections to the frame again ie Rambo earth points.. The Mosfet controlling the heated bed maybe faulty.Always measure resistance from both directions.

Re: Heated Bed Causing System Reboot

Jesse

In addition to Nigel's suggestion, can you please post a picture of the RAMBo board, and the heater connectors.

Peter

Re: Heated Bed Causing System Reboot

I cannot believe this issue has been ignored by Prusa Research as you first suggested. They did get back to you later it seems. However I suspect another issue. Measure the resistance across the heated bed disconnected. How many ohms across the terminals and to the metal earthed metal parts? ie the frame? Then reconnect the heated bed without powering up and measure the resistance again, across the heated bed and from the heated bed connections to the frame again ie Rambo earth points.. The Mosfet controlling the heated bed maybe faulty.Always measure resistance from both directions.

Hi Nigel, thanks for the reply. I tested the ohms as you said, but I came up with some varying results. I just want to double check what you mean by "Rambo earth points"? Would one of the bolts that thread through the printer's metal frame suffice? If not would you please clarify where on the printer I'm taking the reading from. I understand the bed side of the test.

On a separate note, Prusa support decided it was a faulty bed and shipped me a new one. I went ahead and swapped it out for the "damaged" bed, but the printer reset problem persists, leading me to believe the original bed was not faulty either.

Is the Mosfet replaceable or is it part of the RAMBO?

Thanks again for the help!

Re: Heated Bed Causing System Reboot

Jesse

In addition to Nigel's suggestion, can you please post a picture of the RAMBo board, and the heater connectors.

Peter

Peter, hope these help.

Thanks!

Re: Heated Bed Causing System Reboot

Jesse

In addition to Nigel's suggestion, can you please post a picture of the RAMBo board, and the heater connectors.

Peter

Re: Heated Bed Causing System Reboot

Jesse

No, sorry, the pictures don't help...

Therefore back to square 1... PSU voltage switch. With the power off, check it, move it one way then the other a few times and leave it set to correct voltage. Then try again.

The bed resistance should be about 1 to 1.2 Ohms; very difficult to measure. The bed connectors are fine. The reset is probably caused by voltage dropping too much when the heater is turned on - the bed should draw about 12 Amps. Therefore could be a faulty PSU.

Peter

Re: Heated Bed Causing System Reboot

Jesse

No, sorry, the pictures don't help...

Therefore back to square 1... PSU voltage switch. With the power off, check it, move it one way then the other a few times and leave it set to correct voltage. Then try again.

The bed resistance should be about 1 to 1.2 Ohms; very difficult to measure. The bed connectors are fine. The reset is probably caused by voltage dropping too much when the heater is turned on - the bed should draw about 12 Amps. Therefore could be a faulty PSU.

Peter

Peter,

No luck with switching the PSU voltage switch a few times.

Is there a way to test if the PSU is operating properly?

Thanks,
Jesse

Re: Heated Bed Causing System Reboot

Jesse

Not really without switching it out.

Problem appears to be only when a load is applied and ic therefore very difficult to diagnose.

If you have an old PC PSU capable of 20 Amps at 12V, you could possibly rig that up.

Or you could try connecting a different heater to the RAMBo (eg an extruder heater, if you have a spare).

Other than the above, I really am out of ideas.

Peter

Re: Heated Bed Causing System Reboot

Just one more thought...

I can't remember if you tried, but does it only happen with the bed connected? Disconnect the bed and turn the bed heater on to see if a reboot happens. If it does, then there could be a solder short on the underside of the RAMBo connectors.

Peter

Re: Heated Bed Causing System Reboot

Oh, and one more thought...

You now have 2 beds. Connect then in series (polarity irrelevant for this test) then connect the one lead from each to the RAMBo. Turn on the heater to see what happens (double the resistance = half the current draw = should work).

Peter

Re: Heated Bed Causing System Reboot

FWIW, I got a heated bed shipped from prusa that was causing reboots just like you described. turned out they had wired the connector backwards (the part that plugs into the board). I traced it out and I believed all the labels so it appeared correct but it wasn't for the bed. I just loosened the screws in the connector, swapped the pins, and then re-tightened them. It worked perfectly from then and I've been printing for a few weeks now with no issues. I had already checked the power switch like 20 times and checked everything else including the possibly shorted washers. I will probably get rid of the connector and direct solder the bed connectors as several people have had issues with these connectors failing and messing up the RAMBo board.

EDIT: forgot to mention but I received my Prusa around dec 20th timeframe which is near when you got yours, so I wonder if there was a bad batch or possibly a new person mis-assembling them?

Re: Heated Bed Causing System Reboot

Virpobe

That is interesting. I didn't know that there is a potential issue like that with the Mk42 heated bed. There was an issue with the bed shorting and causing this issue with the Mk1's but that was due to the washers holding the bed in place having sharp edges and cutting through the varnish on the board.

The polarity should not matter with the Mk42, but if incorrect, the LED will not light. However, I guess that there is a possibility of one of the inserts being grounded and then polarity could cause this.

Peter