einsy rambo board or heatbed?  

RE: einsy rambo board or heatbed?

@kevin-g13

Did you check the thermistors (bed and nozzle), it's wires and plugs? The thermistors should have a resistance of 100k.

RE: einsy rambo board or heatbed?

Yes, I made sure all the plugs were tight.  Pic 8 (above) shows where the heat bed temp went from 20 to 26 with the hot air test (nozzle 20 to 24).  I just took another reading of the bed thermistor, here is a pic...

RE: einsy rambo board or heatbed?

@kevin-g13

RE: einsy rambo board or heatbed?

@karl-herbert

Thank you for looking at my post and responding.  Unfortunately I have found Prusa support to not be so helpful.  I was hoping to find someone here who could nail down the problem as it were.  The self test may be good for a first setup but this machine really needs a tech-manual and a side set of software for the computer to run, via USB, to give it a once over.  I've had my printer for almost 2 years now and have just over 24 hrs of print time because things keep breaking.  I'm about ready to junk it.  Sorry for being so down but I am frustrated beyond all ends.  Wish you all the best.

RE: einsy rambo board or heatbed?

When you were printing, if your cables flexed at the heat bed connector, you will have broken a wire at that point. Might be intermittent.

The nylon wrapping has to be captured by the connector cover to prevent flexing.

Current builds use a nylon rod up the cable for the same reason.

RE: einsy rambo board or heatbed?

Okay Kevin, 

You are correct that a tech manual and such would be useful for troubleshooting some of the problems that this machine can throw, this one however, is a pretty simple diagnosis since you already own a VOM and appear to know how to use it.  Your question, posed by the subject of your message appears to be "Is the error message "Self test error! Please check: Heater/thermistor not connected" caused by a bad Einsy Rambo controller board or a failed heatbed.

You have already eliminated the hotend thermistor, its connection to the controller and the controller response to the thermistor as likely potential problems by performing the hot air test described above (there is one more possibility yet).  So what now? There are a few simple checks that you can perform with your meter to determine the likely culprit, I would personally perform them in the order below, but you can do them in any sequence you wish.

0.  You indicated in your original post that all fuses were good, did you check them for continuity with your meter or only visually? I have personally had these blade-type fuses be electrically open with no visible damage to the fuse link wire. Assuming all fuses are actually not blown proceed.

Note:  Initial testing will be performed without power so I suggest unplugging the printer for safety sake.

1. Disconnect the heatbed power leads at the controller card and then, with your DMM set to the lowest possible resistance range setting measure the resistance across the heatbed terminals.  As Karl stated above a good heatbed will measure around 3.5 to 4 ohms, the fact that you reported a measurement of zero in a previous post likely means that your heatbed is fine but your DMM range was much too high to measure such a low resistance.  If the heatbed was electrically "open" (i.e. no continuity at all) you would measure essentially infinite resistance here.

2.  Once you have confirmed a good resistance measurement at the heatbed terminals move your meter leads to the ends of the wires that connect to the controller card and perform the same measurement.  If the measurement is similar then, with the meter leads still attached, bend the wires back and forth focusing closely on the area where the wires enter the heatbed strain relief and note whether the resistance measurement changes (this check will test Bob's concern about a broken wire causing an intermittent condition).  If there is no change you do not likely (not guaranteed which I will expand upon later) have an intermittent open in your heatbed power cables.

3.  Now that we have probably eliminated the heatbed and associated wires the next test is to set your DMM to measure DC volts (use the 200V range setting).  Plug the printer in and turn on the power supply. Take care that nothing is in contact with anything that it should not be inside the controller case.  Use the control panel to set a heatbed temperature above the current ambient (40C should do) and measure the voltage at the controller heatbed output terminals, you should measure approximately 24V. If there is no output on these terminals, check the input terminal pairs from the power supply to ensure that the power supply is still supplying 24 VDC to each pair. If you measure voltage on both input pairs but no output from the headbed terminals and the fuse is not blown then you likely have a failed controller board.  Use the chat feature to communicate your findings to Prusa support and see what they have to say.  You may have to purchase a new controller though at this point in time. Turn the printer off again and unplug it when you finish this test.

4.  If you have made it to this point and everything is functioning as expected then there are two more possibilities. 

a.  Possibility one is an intermittent in the heatbed thermistor wire.  Set your DMM to measure resistance again, disconnect the heatbed thermistor at the controller board and measure across the thermistor connector while bending and twisting the wire bundle, once again pay special attention where the wires exit the heatbed strain relief if you see a significant change in the impedance (i.e. jumps to very high) then your thermistor wires are damaged and you probably should replace the thermistor.

b.  Possibility two is that the heatbed power wires have an intermittent not showed up by the low current of the resistance test using the meter.  To test this re-connect the heatbed power leads to the controller, plug in the printer, turn it on and set the heatbed temperature above ambient via the control panel.  With the DMM set to measure DC volts again measure the voltage at the heatbed terminals while once again manipulating the heatbed power leads watching for interruption in the heatbed voltage. Obviously if you see any variation replacement of the heatbed power leads is the order of the day.

Hopefully this series of troubleshooting steps will uncover the cause of your error and you can get back to printing soon.

Regards,

Steve

RE: einsy rambo board or heatbed?

@steve_g

Hell Steve.

Thank you so much for posting a very detailed and easy to follow T/S post.  My apologies for not getting back sooner but I work at a hospital and am pulling a lot of overtime right now.

On to my findings in order of your reply...

Got a different VOM vs the hobby unit I was using.
Fresh Battery

o. Fuses checked good =
Pulled each fuse from socket (1 at a time, put back in same socket), VOM = 0 ohms

1. heatbed terminals at heat bed --- RESULTS
VOM range set to 200 Ohms = lowest setting
I pulled the Heatbed wires off the ENISY board did a continuity test via the wires through the bed and got 3 ohms.
IE: TEST PATH WAS: VOM +LEAD ---> [+ WIRE SPADE OFF ENISY BOARD] ---> VOM -LEAD ---> [- WIRE SPADE OFF ENISY BOARD] == 3 OHMS
Bed temp @ center, also in pic if it matters, was 21.6C
SEE:
Pic 01a-Mar21_20 = heatbed test above: 3 Ohm, 21.6C @ center of bed

Pic 01b-Mar21_20 = heatbed test at copper pads of heatbed: 2.9 Ohm

2. heatbed terminals at end of wires from heatbed to but removed from Einsy Rambo controller do not show an open even when I wiggle them about.  ie: heatbed RED (+) wire lug to ENISY RED lug (+) test of wire only (no change if I wiggle wire about), same for (-) wire.

3. voltage at the controller heatbed output terminals =
Path to temp - Settings
Path to temp - Temperature
Path to temp - bed
Pic 03d-Mar21_20 = screen shows all is OK, bed temp requested is 40C

Pic 03e-Mar21_20 = screen shows PREHEAT ERROR

Pic 03f-Mar21_20 = Voltage at bed 0VDC, Voltage at both power terminals at EINSY are 24.1VDC/24.1VDC

4a. heatbed thermistor wire =
NOTE: I was told by PRUSA SUPPORT that this was bad and to replace it even though I had a good, per www, reading.  Below is the current sensor reading.

RE: einsy rambo board or heatbed?

Kevin,

You are welcome, troubleshooting stuff like this can be a major pain.  It seems pretty clear now that your Einsy Rambo Controller board has failed.  Your next step is to contact Prusa through the Eshop chat and lay out a sub-set of the testing that you have performed (I'm guessing that it might be enough to show the call for heat and the 0V measurement at the Einsy teminals but you have more if they want it.  If you need to purchase a new board let us know about where you are located (at least country :)) and someone here may chime in with a part source more convenient that Prusa.

Regards,

Steve

RE: einsy rambo board or heatbed?

Once again, and you deserve it, thank you for all your help.

I'll be putting all of these notes into my own Tech. Manual for future reference - you brought out a logical sequence for me to follow.

As an FYI for you and anyone else who may be reading I have found the electronics and (other parts) on AMAZON and REPRAP.ME, the links to them are below.

All the best and stay safe.

K.

https://www.amazon.com/FYSETC-Original-Controller-Mainboard-Switched/dp/B07PPN1CTD/ref=sr_1_42?dchild=1&gclid=EAIaIQobChMIi-P2s6rp5wIVCZezCh0XOwXsEAMYASAAEgJKkPD_BwE&hvadid=410012808604&hvdev=c&hvlocphy=9018506&hvnetw=g&hvqmt=b&hvrand=8918374003278063101&hvtargid=kwd-423499490520&hydadcr=21409_11239112&keywords=prusa+i3+mk3+parts&qid=1584892549&sr=8-42

https://www.reprap.me/catalogsearch/result/?q=Einsy+Rambo

RE: einsy rambo board or heatbed?

@kevin-g13

Hey Kevin, I know it's only been a few days since your last post, but I'd be curious to hear your results when you receive your new controller board. 

I'm having the exact same issues as you and I'm curious if it's the thermistor terminal at the controller board that is faulty. My printer is a custom build and hasn't even been used yet. Wish there was a way to test that with a multi-meter. 

Good luck on your troubleshooting and stay safe in the hospital. Everyone thanks you for your help on the front lines! 

Warm regards, 

Chad

RE: einsy rambo board or heatbed?

I'm not trying to hijack your post, but I figured since we are having similar issues I'd post my images / multi-meter readings as well. See link below to images (can't figure out how to embed in thread).

Link to G-Drive

https://drive.google.com/drive/folders/1tJ8TsCBOc25KU74EQ7N-uOGRm7nV_J6F?usp=sharing

RE: einsy rambo board or heatbed?

@csteinke

Hi Chad.

No worries on the post etc.  It has been very, to be polite, frustrating for me in that I saved up for over a year to get the thing and I've had so many things go wrong with it.  Not trying to be angry about my problems but I am a bit... 

Any way.  Just found your post and wanted you to know it may be a bit before I get to repairs now - between time and money.  I don't have the spare $ right now to fix it and have just been put on a 7 day work week (I work at a hospital).  So... I'll do it when I can but I don't know when.

Wish you lots o' luck with your printer and stay safe.

RE: einsy rambo board or heatbed?

@kevin-g13

I hear you Kevin. I bought my printer, 90% built, from Facebook marketplace. I had no clue what I was getting into, but I love solving "hands on" problems, so I thought it would be fun and could benefit my other hobby of homebrewing. Found out what I bought was a Frankenstein build so I've been trying to bring it up to a MK3s.

Slowly working through it. I went ahead and bought a new controller board from Amazon. If that fixes the issue I'll let you know!

Cheers and thank you for your work in the hospital! We're on a "shelter-in-place" here in Denver until April 10th.

Warm regards, 

RE: einsy rambo board or heatbed?

@csteinke

To embed a photo in the post...

1  Click the ADD MEDIA rectangle below the subject line and above the paragraph icons

2  SELECT FILES OR DRAG N DROP

3  it will be added to a group, click the one(s) you want, click insert

RE: einsy rambo board or heatbed?

Noted

Einsy Rambo board - which board should be used?

Needed a moment to wind down before bed and it came to me... Prusa just calls it the EINSY RAMBo board.

.

see their data -- https://help.prusa3d.com/en/article/einsy-rambo-electronics-wiring-mk3-mk3s_2107

.

But I am seeing there is a Einsy Rambo 1.1a and 1.1b.

Anyone know which board should be used, or is better for, the replacement?

Thanks

Einsy Rambo board - which board should be used?

Needed a moment to wind down before bed and it came to me... Prusa just calls it the EINSY RAMBo board.

.

see their data -- https://help.prusa3d.com/en/article/einsy-rambo-electronics-wiring-mk3-mk3s_2107

.

But I am seeing there is a Einsy Rambo 1.1a and 1.1b.

Anyone know which board should be used, or is better for, the replacement?

Thanks

RE: einsy rambo board or heatbed?

So I ordered and installed a new board today and it didn't make a difference, I'm still getting the error. 

I'm now trying to troubleshoot by going to settings-->Temperature-->Bed--> turn up to 100. Then go back to info screen and see if the bed starts to heat, mine isn't, and I get a "Bed Preheat error" which makes me think the bed is bad.

Currently trying to further troubleshoot this, will update. 

RE: einsy rambo board or heatbed?

@csteinke

The heating bed of the MK3 (24V) should have an internal resistance of about 3,5 ohms. I would measure that once.