Suggestions wanted | repair, upgrade or ditch?  

RE: Suggestions wanted | repair, upgrade or ditch?

Hi Chuck
have you flashed the correct firmware if not probably a good idea first

test the heatbed again...

best find what fried.

if the firmware was a standard updated prusa firmware, it should not have fried the controller.
the heatbed should be pretty resillient, unless the build plate has scratched the paint off and shorted the tracks

if you haven't done anything else. the most likely issue is the heatbed power cables, or the power connections

I suggest that you visually check the heatbed connections, the Einsy power connectiona and the power supply connections for any signs of over heating

these connections and wires are probably the most likely to fail due to repeated motion, or incorrect assembly

Check the power supply output voltage. should be 24 volts on each pair of power connectors...

heatbed resistance  should be around 3 ohms.

test hot end see if it works,

test filament sensor 

test pinda

check motors move

check the three fuses on the einsy.

Is it a silver power supply?

Best chance  Power wires need replacing, 
or fuses need replacing

Worst case Mk 3.9  upgrade, or replace printer... 
MMU3 is better than MMU2

regards Joan

RE: Suggestions wanted | repair, upgrade or ditch?

Hey Joan

Thanks for taking the time to read and answer. -

I think I found the culprit - Here is the chronology :

The gripes started after downloading and upgrading to "prusa3d_fw_3_13_2_MK3S_3_0_1_MMU2S.zip"*,
which caused a number of finda related error messages. (the update was part of wanting to integrate the printer in prusalink)

I managed to get the filaments to load correctly again.
However, the follow-up problem was that the print would fail right before the purge line,
ending up in a large blob - and that is exactly when I first realized a pungent smell.

I contacted support concerning the blob problem.
The verdict was "wrong firmware" and they sent me a link to "prusa3d_fw_MK3S_MK3S+_3_13_2_7080.hex", which I installed.

Another attempt at printing ended in unusual stress on the MMU filament loading system that quite laboured
to produce a metaphorical 'fat python' under the nozzle instead of the regular thin mamba.

Ever since the red light at the heat bed connector won't show up, bed heating is dead.

@tests:
- hot end: OK
- finda: OK
- motors move: OK
- pinda: Um, thought there's only the finda with the MMU2
- power supply: silver, yes.
- 3 fuses on einsy: look OK
- heatbed resistance: dunno where to check that

@CLUPRIT
- the left einsy headbed connector is fried --> see attached pics.

So, from this new perspective, what's the verdict now?

Ta
Chuck

* consists of:
- prusa3d_fw_MK3S_MK3S+_3_13_2_7080.hex
- prusa3d_fw_MMU3_3_0_1.hex

p.s.:

I just realized that I was advised to install a firmware that I already had running ..
It appears to me that the heatbed incident somehow coincided with the filament loading probs after the update(s).

RE: Suggestions wanted | repair, upgrade or ditch?

Try replacing the heat bed wires. I use 16awg flexible silicone insulated wires. Like used for RC car batteries. It's more flexible than prusa wires. 

If you can't crimp the end connectors. It's likely that your nearest car repair shop can do it for you

Make sure the connections  are tight. And you should be good to go.

RE: Suggestions wanted | repair, upgrade or ditch?

Yeah, that sounds like the most sensible thing to do.

I've realized though that the cable per se is only fried until shortly after the cable shoe.
I am tempted to just pinch it off right there and crimp on a new cable shoe.
The cable length then should still be sufficient and it would save me from unsoldering the old wire from the heatbed.

BTW: Excellent idea with the wires from the car shop. I 'll keep that in mind in case it becomes relevant.

I hope I'll get around to it at the weekend..

Many thanks for your advice, Joan.

Chuck

RE: Suggestions wanted | repair, upgrade or ditch?

you have an early Mk3 then...

heatbed is screwed on now!

RE: Suggestions wanted | repair, upgrade or ditch?

I can see why they left the soldered version behind..

The spare cable shoes won't arrive till Monday.
Meanwhile I've decided on dismantling the MMU2 and return to the good ol' MK3s version.
I hope the 'lazy approach' from 2021 that I found here will take me to an acceptable solution..
So, unless you have a better idea, that will be my next step.

RE:

It's alive! Again..
The MK3 (minus MMU2) is back in the game.

The beauty of Prusa bed slingers is that imho their (relative) simplicity facilitates longevity.
Friendly and competent community advice (though seldom needed) is just a click away
and repairs are likely a matter of removing and re-fastening a couple of screws. -
Thank you Joan.

With that said I'd like to add that the cause for the fried cable is not quite clear.
I can only assume that the finda sensor failed to trigger, which made the nozzle extrude near the bed till it choked, thereby overburdening the system.
In 7 years the printer has never had so much as a hick-up, with the exception of the occasional print going south. (MMU2 related, of course.)
Which kinda makes me wonder whether the incident is due to some sort of 7-year-itch, or whether that firmware update .. never mind.

Happy again.

Cheers
Ch