Shorted Thermistor/Rambo on Rostock - Need advice

[cassetti]

Hello Everyone!!

Long time no see, haven't been active on the forum as I haven't done anything with my Rostock in months, actually my Rostock has been down for almost 5 months now!

Long story short: Back in June/July I had finally gotten my Rostock mostly dialed in, really the only issue I had was my lack of a proper PEEK fan, and my hotend running a bit cool (no problem, simply set the Slic3r temp settings for the hotend a bit higher!). I decided to start on a new 20-hour print of a vase (4 shells). Everything was going fine for several hours, so I went to bed. I woke up next morning to a printer fully stopped. I don't recall what happened, but it appeared the printer was still on, but the hotend was not moving around, and not extruding. But the Repetier host still indicated it had 1 hour left of printing!

It appears my print must have warped up, and the hotend hit the print. This at some point in the night shorted the thermistor leads against the power resistor leads! Now when I turn on the Rostock, I get a temperature reading around 10C - but it fluctuates, even increases when I turn on the temperature. However the Rambo has now one strange side effect: The hotend NEVER turns off!!! If I set the temperature to 100C, the temperature will reach 100C (according to the dead thermistor), but the hotend will continue heating up!! Even sending the heaters-off command does not work! Note the Onyx bed works just fine, no problems with this.

I wanted to fix the printer at that time, but unfortunately I had a cracked foundation in my house. As such, I had to tear apart my basement and fill my workshop/bench with stuff. Only last week have I finally finished cleaning and organizing the whole basement! Now it's time to finally get my Rostock back up and running! I miss having a working 3D printer in the house.


So, here's where I need some advice. Obviously my Thermistor sensor for extruder1 is shot. Since the Rambo was built for 2 extruders, I suspect I can simply re-wire and update the firmware.

I am planning to follow Geneb's revised assembly manual and going to re-build the hotend. I believe I didn't properly install the power resistors with aluminum foil (not tight enough). This time I plan to take my time and do it right! I have also purchased the quick disconnects per his suggestion in the manual.

Now here's my question: I need to update the firmware. Since my printer is one of the older versions, should I simply flash with the old firmware I have saved on my computer, or should I update to the latest firmware? I had everything dialed in with Polygonhell's firmware, is there any need to update if it was working fine a few months ago?

Also, are there any improvements to the design that I should consider upgrading? IE, I see the delta arms and platform have been sanded now to eliminate the delta arm blues. I over-sanded mine and had to use shimming washers to get a good fit. Should I call SeeMeCNC and purchase the newer ones?

Thanks for the help guys! I'll have all the hardware I need by tomorrow to rebuild the hotend. Hopefully I didn't completely fry the Rambo!

[geneb]

I'd like to move the post as requested, but I have no clue how.

g.

[Eaglezsoar]

Here is my opinion for what it is worth.
I would make it workable again exactly the way it was, I see no reason to upgrade anything until you get it running again, at that time you are better
able to determine what upgrades you would like to do. If you try to upgrade firmware, parts, etc you will be constantly trying to figure out why something
is not working. I probably would make the following exceptions:
1. Change from resistors to a heat cartridge
2. Change to a threaded thermistor if you have a 3mm tap and a 2.5mm drill bit

[cassetti]

Here is my opinion for what it is worth.
I would make it workable again exactly the way it was, I see no reason to upgrade anything until you get it running again, at that time you are better
able to determine what upgrades you would like to do. If you try to upgrade firmware, parts, etc you will be constantly trying to figure out why something
is not working. I probably would make the following exceptions:
1. Change from resistors to a heat cartridge
2. Change to a threaded thermistor if you have a 3mm tap and a 2.5mm drill bit

I hear ya, that's my thoughts exactly.

Heat cartridge? Will that fit into the existing hotend or do I need to buy a new one?

I'll just stick with RTV to hold the thermistor in place for now. Fortunately I have tons of Kapton tape to hold everything together. And Geneb's new assembly instructions show a much cleaner install than my previous assembly.

Hopefully I didn't completely fry the Rambo and extruder2 still works properly!

[Eaglezsoar]

A heat cartridge will fit the existing hotend but note you only need one, the other hole on the hotend would be empty.
The advantage is that the cartridge virtually stops the possibility of shorts that are so common with resistors, quicker
heat times in most cases. Ebay is full of listings for them, a sample link: http://www.ebay.com/itm/New-3D-Printer- ... 20d76f9c95

[cassetti]

A heat cartridge will fit the existing hotend but note you only need one, the other hole on the hotend would be empty.
The advantage is that the cartridge virtually stops the possibility of shorts that are so common with resistors, quicker
heat times in most cases. Ebay is full of listings for them, a sample link: http://www.ebay.com/itm/New-3D-Printer- ... 20d76f9c95

Cool, I'll keep that in mind. For now I'll stick with the power resistors. Heatup times on the hotend are insignificant.

Heating up the onyx on the otherhand..... really wish I had something with more juice to heat it up to 100C! Right now I can barely hold 80C

[Lochemage]

Before you do that, I would first make sure that the thing that shorted wasn't your RAMBo instead of just the thermister. I'm not sure how to test for this, someone else may be able to help with specifics, but take a close look at the RAMBo and make sure you don't see any obviously melted/blackened areas that shouldn't be there. Then, make sure all your wiring between your thermister and heat resisters aren't touching exposed wires anywhere around that area (or touching the metal of the nozzle itself). If you didn't use PTFE tubing to insulate the heat resisters, then they are very likely to be touching the metal nozzle if they were bumped hard enough.

[cassetti]

Lol, I can still use my Rambo, it functions normally.

I've done this before, I know what happened. My power resistor came into contact with the thermistor, and partially fried the thermistor sensor on the Rambo.

I've done this before on two different control boards, though those were on the beds, not on the hotend.
My hope is that when I wire the hotend to extruder1 (the second extruder), I can reconfigure the firmware to use that extruder instead.

If I didn't, guess I'll need a new Rambo. Either way, I need to re-wire the hotend. Using GeneB's instructions from March resulted in some nasty loose crimped connections. I can tell I've got a slight short in the connection to the bare power resistor wires. This time I bought a new crimper and butt connectors.

I figure after 160 hours print time, it's finally worth tearing down the hotend and re-wiring. Although, I'm going to look into those heater cores, and try that instead.

Hopefully I'll have the Rostock running in time for printing Christmas gifts!!

Can anyone tell me, has much changed to the Rostock firmware since March? Still debating if it's worth updating or not after I get the printer back up and running