Reddit mentions: The best circuit protection products

Depending on how adept you are at dealing with electronics, you might consider popping the power supply open and looking for burnt NTC thermistors. An NTC thermistor is a device that is used as a current inrush limiter. When you plug 120V devices into 230V outlets that is often what goes first. If there is a fuse that may have gone as well.

NTC thermistors are both common and cheap and if you have an old dead
ATX PC power supply you probably have one in there already.

But yeah, the power supply is most likely the problem and a replacement is definitely worth a shot. It's possible you can fix the power supply yourself too though if you want to take a look. In these cases it's often possible to see parts which have literally burnt making it easier to identify the problem.

EDIT: (A disclaimer of sorts)
And please remember to use common safety guidelines when working with AC connected devices. A new power supply is probably the cheap and fast way to go for most people and almost certainly reasonably priced on-line but if you're interested in learning about power supply repair I recommend the topic and the NTC trick is one that has saved me a few times. I learned about stuff like that from resources like DiodiesGoneWild, (Amazing!) ElectroBoom, BigClive, PostApocalyptic Inventor etc. There are so many great electronics resource out there these days and that's more the nature of this question than for an electrician. Good luck and play safe.

Here is a typical-looking one in a photo on Amazon

https://www.amazon.com/uxcell-Thermistor-Resistors-Current-Temperature/dp/B07KZZ8WV8

On an ATX power supply you will often find them near the part where the AC lines are going into the board before the big capacitors.

In this photo you can see a pair of blue NTCs on the bottom left corner right between the fan and the bridge diode.

https://i1.wp.com/makezine.com/wp-content/uploads/2014/04/img_2737.jpg?resize=1024%2C575&ssl=1

H and L makes sense, it would seem it uses normally-closed switches instead of normally-open ones, but it's the same basic principle. H stands for High signal, L for Low. As far as your endstop is concerned, if you want to try plugging them in backwards, you can, but I don't think that'll change anything, as your models seem to be bare switches, so there's no polarity. You could try using a multimeter to test continuity of the switches though. It's also possible that the RAMPS board itself isn't registering it correctly. If you want to test that, you could always pick up another RAMPS online, plug the wires and drivers in exactly the way they're currently plugged into your printer, then swap it with the old RAMPS board on the Arduino. The RAMPS itself just routes power and signals, and has no firmware of its own. This means your firmware won't notice if you've changed the shield on top of it to one with the same layout. I've linked the specific model of RAMPS I use on my prototype printer, which has minor improvements that don't change how it interfaces with the board (specifically, the fuses are a bit bigger, which helps with some problems surrounding running the heatbed and higher powered steppers). You can also change the stepper drivers to these, or another daughterboard that uses the A4988, without any changes to the firmware. It's quite possible the driver boards fried at some point, either with a trim pot adjustment shorting them out, something to do with that second potentiometer changing a setting (from what I can tell that was used to manually set something that's since become completely automatic on these driver boards), or some other issue, as they can be a bit fragile. Luckily, they're cheap, haha.

In response to your earlier question about putting an SD card in, if you want to, go for it. It won't hurt anything. It'll get rid of that error message, for sure. I don't think it'll do anything else of importance, but there may be some quirk of that specific SD card board I don't know about, so there's a possibility it'll be more compliant with one in there.

Oh, okay, I just thought of something. When you're running the machine, is the bed hot while it's turned on? the M105 command you see the machine continuously running is it probing the bed and hotend to see what their temperature is. It says B: 120, which means it thinks the bed is heated to 120C. If the bed isn't heated at all, it may be reporting a fault, which could make the machine not respond to your commands. If you want to test this, next time you turn off the board, unplug the bed's thermistor from it, and turn it on. See what the B value returned after M105 is then. If it's still either reporting 120, or some other crazy number, you may need to replace it with something like this. That may not be exactly the right thermistor, and may report weird temperatures like 60 or 10C at room temperature, due to the tables being slightly mismatched, but it should work well enough for testing, and later on, if the firmware gets changed, it'll be a known variable, so that's not an issue.

I know I've linked a few things to buy, so you may be thinking "bah, I don't want to sink money into this thing if it's this old anyway," but it's worth mentioning I'm only going to link modern components. If there ends up being a point where you just want to throw your hands up and give up working on this i2, every one of the parts I'm linking you is something used by some of the most recent printers around while still being compatible with your current device, so you're not just throwing cash away on legacy tech. Also, in the event that this thing just won't work as it's currently built, I'll happily print out and send you the components necessary to build a totally new one that reuses as many parts as possible from your current i2. Pretty much all I do is design printers, make prints for other people, and give support/advice when it comes to working with them, so I've accrued tons of spare parts that're compatible with a wide variety of things, and you'd not be the first person that's received a box of most of the components necessary to rescue a semi-functional printer out of my spare parts bin and printed out using the end of a few spools I can't use for anything major.

I recently went through exactly this same situation. I was ready to upgrade to a microswiss all-metal hotend and the catastrophic failure of the print leaving gunk all over my heater block forced the issue. In my case, I opted to replace everything I could including the thermistor and heating element. They are both very inexpensive and you should have a spare laying around anyway in case you need one in a hurry. So...how to clean your heating block...

Fire. Seriously. I used a combination of blowtorch and solvent to remove all the gunk (and mine was a LOT worse than yours...it basically encapsulated one entire end of my heater block, entombing the thermistor, heater and associated wiring).

I used your typical propane torch, holding my heater block in a vise or vise grips. I'd heat it up then quickly wipe away the melted PLA with a clean cloth. Heat, repeat. Then I'd soak the whole thing in some solvent (acetone, MEK, etc). Repeat until clean. Pay careful attention to the tiny setscrew that holds the heater in place...work it free with a hex wrench while it is hot...chances are you got some PLA stuck on there, too. Obviously be super careful when you do this. Ventilation, fire-extinguisher handy, your mom on speed-dial.

When you replace the thermistor and heating element you'll need to do some soldering. This is pretty unavoidable. Those elements come with very long wires attached to them and the Wanhao/MP print heat doesn't need that length. Clip it short, make good solders and use heatshrink over your joints. For the thermistor I simply cut out the center section of the wire and spliced the connector back to the component at the length i needed.

Now, when you put it all back together you will have the option of re-wrapping the heater block with cotton and Kapton tape. People seem split on if this is necessary, but since I'd battled heat creep before I didn't want to introduce any more heat up the block...so I opted to do it. It's a bit tricky if you get the non-punched cotton strips like I did. Luckily I had hole punches handy to make the provision for the hotend and nozzle to get thru the insulation. If you don't have these tools (or don't quite know how to do it), i'd shop around for pre-punched sets.

good luck. Let me know if you need any more help.

here are the parts i used:

https://www.amazon.com/gp/product/B071K8Z9KF/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B01N4KY6TR/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B076NW3GNH/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B01E1HANLS/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

I did the same thing while changing a nozzle. I ordered https://www.amazon.ca/gp/aw/d/B01N4KY6TR and it was a perfect replacement for my v2. Pretty easy to replace too, just involves some unscrewing of the casing and running the new wire to plug it in (no soldering required).

Use this as an opportunity to stock up on a few different spare parts. I recommend always having those tubes, nozzels, heaters, thermistors, and possibly even one set of spare cooling fans. I did one purchase a little over a year ago, was like $40, has saved me from having downtime on several occasions.

Thanks. Currently installed is a 3 year old evergreen x13 .5HP 230v motor in there. Have you had any luck replacing any individual components like the thermistor (inrush current limiter?) https://www.amazon.com/Ametherm-Thermistor-Inrush-Current-Limiter/dp/B071D326TB.

It's so weird that after 24 hours the fan stops working and I just need to shut the circuit breaker off for a brief amount of time turn it back on and it works for another day

You should use the continuity tester of any multimeter to check the wires before replacing them. You can connect one lead to where the heated bed wire plugs into the motherboard, and the second to where the other end of that wire is on the heated bed. Do that to check all four wires while jiggling them around to check for internal breaks.


If all four wires going to the heated bed are well connected you probably have a bad thermistor. This is that little black thing mounted to the center of the heated bed that measures the temperature of the bed. You can connect an ohmmeter to either side of the little black thing to see if it gives the correct amount of resistance (in the neighborhood of 100k ohms)


I had to replace mine, you just need any 100k ohm glass bead thermistor, it doesnt even have to be the same exact type as the one on the board. I used this one:


https://www.amazon.com/gp/product/B01N4KY6TR


it has leads and a plug that i plugged directly into the motherboard and just taped it to the bottom of the heated bed with kapton tape and works perfectly.

Good luck!

I had installed new thermistors after the degrees went to -14. I just went out and bought a multimeter, checked the thermistor (I think correctly) and it showed 105 which makes me think the new thermistor is good to go. I don't know what I would be looking for if it was a blown capacitor, but as far as I can tell it looks good.

​

I did update the marlin sensor number to 11 per what amazon said it was, and it made the numbers in the fluctuating 900s which didn't seem right at all (obviously), but maybe it was a step in the right direction? Here is a link to the one I bought. I made the purchase based off one I saw on gearbest.

I grabbed these for my Ender when I had a similar issue. Always great to have a few extra on hand.

https://www.amazon.com/dp/B01N4KY6TR/ref=cm_sw_r_sms_awdb_t1_Fc0UCb9KK5K1E

I just got these when I replaced mine earlier this year, and they work great

easy and cheap enough to just get new ones and new thermistors

https://www.amazon.com/gp/product/B07C3N3M52/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

Thanks for the suggestions! The Maxiwatt hot end looks impressive! I may have to try it out sometime. I just have a couple more questions:

• Is there anything I can do or buy that will help me from breaking the thermistor as I'm installing it?
  
  
• I found a pack online, but I don't know if they're the same as the stock. Stock thermistor and thermistor multipack. Are they the same? If not, how would I adjust the firmware to make it work?

Not sure if I was lucky or if it is an old image but these I purchased off Amazon actually had the white connectors already attached which plug directly into Mini's board.

https://www.amazon.com/gp/product/B01N4KY6TR

Just removed the old one entirely and replaced it with one of these. Splicing anywhere along the area that travels up and down as well as left and right is going to wear the spice after time. If you do have to splice or solder any of these wires make sure the point of the splice is somewhere inside the Mini's structure and not with the Bowden tube so there is no constant flex on it.

A quick google search for your specs led me to this 12V, 400A breaker for $13.

Auto winches seem pretty common, so I would think there's lots of options out there.

My first guess would be your thermistor being messed up. Make sure it has a solid connection to the board, that none of the wires are kinked or damaged, and that it's properly seated in the heating block. If all that checks out then I would bet it's busted. These Anets were built on the cheap so that wouldn't totally surprise me. You can replace it with something like this. Good luck!

Or this may be what you need: https://www.amazon.com/Honeywell-393691-Gas-Valve-Conversion/dp/B003WZS8K4

(edited for better link on Amazon)

That's a good idea on the thermistors. I recently picked up 100 for about $10 and are very simple to implement.

Bi-metalic thermal cutoff switches can also be used.

If you bought one of thos $10 clones I think it would be better just buying the cables to your regular direct drive extruder that came with the printer, I bought one these thermistors and I also bought this heater cartridge. There is also this one that comes with 5 thermistors and 5 12v heater cartridges for $12.

It's possible that you forgot to switch the jumper back from USB to VREG. That would explain why the printer is only turning on the lcd and thermistor when plugin in the usb cable.

Yes That is the one I got.

https://www.amazon.com/Anycubic-Thermistor-Wiring-Printer-Heatbed/dp/B01B41K7OM

Go ahead and buy some spare thermistors. I hear they go bad pretty quickly. I bought them in bulk :)

https://www.amazon.com/gp/product/B01B41K7OM/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

probably not worth the hassle of sending it back, you can get a 5 pack of thermistors for like 10 bucks.

https://www.amazon.com/Sunhokey-printer-Thermistors-Connector-Printer/dp/B078GMLYPK/ref=sr_1_11?s=industrial&ie=UTF8&qid=1518479228&sr=1-11&keywords=ntc+3950+thermistor

I just did the same thing while making a different upgrade. I'm trying Muffler Sealer to put it back in (hasn't arrived yet).

Edit: also replacing my thermistor with this one.

here are some usable thermistors, unwired and unshielded. 100 for $5.46 in case you have a reason to make more than one and are handy.

http://www.amazon.com/SODIAL-Temperature-Measurement-Thermistors-MF52-103/dp/B00HUHC4UU/ref=sr_1_9?ie=UTF8&qid=1421154388&sr=8-9&keywords=NTC+10K

That is the thermister.

https://www.mpselectmini.com/parts/thermistors


https://www.amazon.com/Sunhokey-Printer-Parts-Thermistors-Connector/dp/B078GMLYPK/ref=sr_1_14?keywords=100K+NTC+resistor&qid=1557635651&s=gateway&sr=8-14

How about 5 for $9?. Or 10 for $10. You may have to change your firmware to use a NTC 3950 100K thermistor (very common).

This is the one I have used. [Link] (https://www.amazon.com/dp/B01B41K7OM/ref=cm_sw_r_cp_apap_XvQ258yKiNyW9)

Here’s the links to the things I bought.
Heater cartridge
SEFUSE
HeatBlocks, Nozzles, Heatbreak
100K Thermistor

Get this pack of Thirmistors now. having that break on me really sucked and it seems to be a problem for others also. I would say the next big thing I did was a new knob. A world of difference.

I personally love this little printer. I don't do much to it but it's there when I need to print parts to fix the other ones.

I used this one:
https://www.amazon.com/gp/product/B01B41K7OM
It wasn't the exact same connector, but it fits fine. Same thermistor, no need to change settings.

Something like this is all you should need. The problems arise when switching to the cartridge style thermistors that come with E3D hotends. They're supposed to be more durable and accurate, but require tweaking the firmware. The ones I linked to should just plug right in without any extra changes.

If this isn't a problem from you previously modifying anything related to the thermistor, i would just replace them. Mine was reading 999 and I bought a few off amazon for about $8 iirc and it fixed the problem.
https://www.amazon.com/dp/B01B41K7OM/ref=cm_sw_r_cp_apa_Wn7WBb1NMNEWR

You mean like this stuff? I have a can of it and it's expensive shit, but havn't used it on anything sensitive yet, so not sure if safe or not.

I could be wrong, but I believe you are talking about the heatbed thermistor. What makes you think you have a short in it?

The tape is holding it against the bottom surface of the bed. It's not attached in any other way. You can buy 5 for $9. Not sure if you will need to change the firmware configuration for these thermistors.

I must have on accident, I was fiddling around with the screw because I couldnt get it correctly because the wire didnt want to stay in the hole and must have came out a bit to be pinched by it, and I heard a crack and looked, and all was left was copper on the wires

​

Guess I need new one now, https://www.amazon.ca/Happisland-Thermistor-Wiring-Printer-Heatbed/dp/B01N4KY6TR/ref=sr_1_7?crid=32XZGNIRBJ19S&keywords=100k+thermistor+printer&qid=1558652602&s=gateway&sprefix=100k+ther%2Caps%2C155&sr=8-7


Are these any good/ the same and hopefully not catch my house on fire?

The old thermistor broke. I used alleged drop in replacements that I found on mpselectmini.com. These are the ones I used. https://www.amazon.com/dp/B01B41K7OM/ref=cm_sw_su_dp I should note that the thermal runaway occurs without even setting a temperature, it just starts heating and that's that. Someone on FB said it could be a bad driver, but I am not sure how I would go about testing that with a meter or scope

I had this same issue a couple months ago. My thermistor on the extruder was busted (specifically one of the tiny wires to the very tip was snapped, but still making poor contact). 8 bucks on amazon for a pack of 5, ten minute swap, no issues since.

This is what I bought: https://www.amazon.com/dp/B01N4KY6TR/ref=cm_sw_r_cp_apa_i_Kg9qDbKNPFPMQ

I misread your post and posted a bad reply, deleted.

I agree with /u/LosinCash, it's probably the thermistor. It may not be properly contacting the heater block, pull it and check it's into the hole properly.

Also be careful those wires are brittle and easily broken. Another thing to watch for is that the wires don't contact the heater block.

Here's a link if you need some new ones:

https://smile.amazon.com/gp/product/B01N4KY6TR/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

You don't need a whole hotend unless you planned to upgrade it anyway for running hotter plastics (All metal hotend like the E3D)

EDIT: Oh yeah - the screw that holds the thermistor does NOT screw down on it!! It's GLASS. The washer holds the wires to keep it in the hole.

PuterPro

Thanks for the input. Is 100K standard for most printers? I couldn't find anything in the manual except a tiny picture of it and I cannot read what it says on the thermistor. I found this one on Amazon but I would prefer not to buy the wrong thing as I'd have no other use for it but my printer.