My dearest MK3 - a sad story with no happy ending (at least for now...)  

Re: My dearest MK3 - a sad story with no happy ending (at least for now...)

I can see the images now. (I don't log into any social media, including google.)

Yes, that is one nasty BOD... 😯

Re: My dearest MK3 - a sad story with no happy ending (at least for now...)

This is a sad story ...

Nice written story but I don't see nothing sad about it. You had just a blob. It does look always impressive but at the end an easy and not to expensive fix. Many people had this and there will be many more to come. It's pretty common user/usage error. Even if you can't rescue any part from the head, it costs assembled $80. Just for comparison: UM3 Print Core($115), UM Complete Print Head($410)

What I'm trying to say. Any 3D printer requires repairs over the live time. Don't be angry or disappointed. Repair it, learn from it, go on using it. I keep track of my repair costs and for my two Prusa printers with all the repairs needed, I still spent less then base Ultimaker 3 price.

Re: My dearest MK3 - a sad story with no happy ending (at least for now...)

Thank you all for your suggestions and suport how to deal with this hellish blob (@corey.d3; @nikolai.r) and especially to @bobstro for your always prompt and helpful responses!

So I did it! I did remove the blob sucessfully without breaking electric cables (which was my biggest concern). I need now to clean everthing carefully and put together again.

We shall see if my dear MK3 will get well soon... and what's more important ... if she will be kind to me - printing what I desire to print...

PS. Thanks @nikolai.r - i feel like I've been learning A LOT during last 2 months and these are sometimes a really tough lessons. But I'm not going to give up!

Re: My dearest MK3 - a sad story with no happy ending (at least for now...)

Welcome again..

After a few weeks of successful printing (when I was able to print the parts that I wanted) I encountered another issue and my printer is dead again 🙁
I somehow broke the heater cartridge and hotend thermistor so I replaced both parts but unfortunately the hotend doesn’t heat.

During the self test procedure I got the error “Thermistor is not connected” but I’m pretty sure that it has more to do with the heater, because:

So my question is – what, when and how I should check with the multimeter

Your help is badly needed again
Many many thanks!

Re: My dearest MK3 - a sad story with no happy ending (at least for now...)

Maybe you accidentally damaged some of the thin cables when assembling the extruder?
I know from my own experience that it is extremely easy to pinch the cables when mounting the X-carriage-back.

Twice I destroyed the cable to the printer fan, and once i destroyed the thermistor cable when I incorrectly mounted the cable package to the RAMBo housing.

Re: My dearest MK3 - a sad story with no happy ending (at least for now...)

did you check the fuses in the controller ? pull them and do a continuity check; something I have seen with this automotive type of fuse is that they can fail and still look ok.

Re: My dearest MK3 - a sad story with no happy ending (at least for now...)

@randolph.l Actually it came to my mind just before your post ... and indeed - one fuse (5A) was fried. I read that one of these 5A fuses are responsible for thermistor.

So - tomorrow I'm going to replace the broken fuse. In the meantime I checked the resistance of the heaters
1. Original MK3 - 24V 40W - 15 Ohms
2. My replacement - 24V 50W - 11,8 Ohms

So I assume that the heater is OK, thermistor is OK and the problem was the broken fuse. Do I understand correctly that with the fried thermistor fuse the heater can't heat? It's seems to be logical - in order to prevent uncotrolled temperature rise.

Thanks!

Re: My dearest MK3 - a sad story with no happy ending (at least for now...)

grab a few fuses in each size just in case they are handy to have a bout and most cars use the same design.

the difference between a 40w and 50 w heater at 24 volts might push you over the current needed to blow the fuse I would doubt it,

I would expect the design of the circuit to allow for a 25% increase in heater requirements

Re: My dearest MK3 - a sad story with no happy ending (at least for now...)

HA!

I replaced the broken fuse and run the self test - again I got the message that the thermistor is not connected. But then I realized that I had forgotten to connect the heater to the board. So I did so and it worked!

The selftest was passed! The heater and thermistor works.

Many thanks again - I really appreciate the supportive community of Prusa users!