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Tried it, also remapped the thermistor pins in pins.h to try all 3 ports (one of my ports was already dead). So far, nothing I've tried has uncovered the problem. Looking at the schematics, the ports are very simple, perhaps the small caps blew.

Ouch. That sux. I would think it's something bad on the board.

It sounds very similar to a problem I had in the beginning with my first 3d Printer. With that one I had to solder the components onto the RAMPS board. I would consider myself an advanced solder-er. But I had to solder and de-solder components numerous times, almost gave up on that board but got it working the 5th time around.

It was something similar to your problem in the thermistor readings, negative degrees and such. I finally tracked it down at one of the headers I had to solder and re-solder a few times.

Just double checked both thermistors and they are definitely giving proper signals at the connector to the RAMBo. If I touch the area where the thermistor is on either the hot end or heated bed, the resistance drops as expected. So it looks like I have 4 bad thermistor ports now. Not sure what happened but likely something while I was replacing the bad hotend thermistor.

I have an extra RAMPS 1.4 that I guess I'll try to get running this week.

did u work on it while it was powered on? how could all of them get shorted. hmmm. check the little fuse maybe?

This is exactly what I had going on with my thermistors. Including the remapping leading up to it. I had to replace my Rambo.

Ouch! Oh well, the Max and I laughed together, cried together and made some beautiful prints together.

I have disconnected everything and have the card laying on my static free work surface getting ready to scope it. I've gone through the schematics but for the life of me can't find what those 2 little rectangular fuses protect.

If you do figure it out, please share!

I suspect it is a failure to tthe inputs of the main process itself on mine.

I guess this is a great arguement for modular controller boards with replaceable systems on them.

mhackney wrote:Ouch! Oh well, the Max and I laughed together, cried together and made some beautiful prints together.

I have disconnected everything and have the card laying on my static free work surface getting ready to scope it. I've gone through the schematics but for the life of me can't find what those 2 little rectangular fuses protect.

I looked at it myself I wasn't sure either. its hard to tell from the schematic but my guess is the thermistor circuit isn't fused.

Heated Bed, 15A 12-24V (version earlier than 1.1 limted to 14A 16V due to fuse rating, see rambo_development for hacks)
Extruders and fans, 5A 12-24V (fuse can be exchanged for up to 10A capacity) 10V-26V input voltage
Motors and logic, 5A 12-24V (fuse can be exchanged for up to 10A capacity) 10V-26V input voltage

I'm guessing thermistor would be under logic. so if your motors are working then the fuse is good..ey?

Unfortunately, modularity can only be taken so far. None of the other controllers are modular at this level. RAMPS is only modular at the Arduino / stepper driver / main controller level. Plenty of people have screwed the pooch with RAMPS too!

mhackney wrote:Yes, I have not done this in the past but this time I wrapped with Kapton tape to keep it in there.

I thought when I ordered a batch (20) of the cartridge heaters I saw a similar cartridge thermistor or thermocouple on eBay. But now I can't find them. Anyone seen these?

Ebay item 221198834208 is not a thermistor cartridge but is a pre-wired thermistor along with a heater cartridge. Maybe that is what you saw.

-B

mhackney wrote:Just double checked both thermistors and they are definitely giving proper signals at the connector to the RAMBo. If I touch the area where the thermistor is on either the hot end or heated bed, the resistance drops as expected. So it looks like I have 4 bad thermistor ports now. Not sure what happened but likely something while I was replacing the bad hotend thermistor.

I have an extra RAMPS 1.4 that I guess I'll try to get running this week.

It' unfortunately possible to destroy the ADC on the arduino, there is only one, the multiple input pins are just multiplexed. It's also very easy to do, they are very sensitive to any excess voltage but usually you just blow the input not the ADC.
If you're getting 100K OHMs give or take at room temperature from the thermistor, and connecting it doesn't give you a valid reading, there isn't much else you can do, short of replacing the microcontroler not be board, even if you do that you'll need someway to load the boot loader.

Thanks Polygonhell, that would explain why all 4 ports are now dead. One should have been unaffected since nothing was connected to it and it was "known good" over the weekend. Time to hook up a RAMPS. I bought 2 of these in January at a great price and was planning to use it in a home brew delta printer.

@Broose, thanks, I found the item (finally) that I saw: PT100 platinum resistor.

mhackney wrote:Thanks Polygonhell, that would explain why all 4 ports are now dead. One should have been unaffected since nothing was connected to it and it was "known good" over the weekend. Time to hook up a RAMPS. I bought 2 of these in January at a great price and was planning to use it in a home brew delta printer.

@Broose, thanks, I found the item (finally) that I saw: PT100 platinum resistor.

Those Thermistors you found may work with a custom table but they are 4mm in diameter so they will need to be wrapped a lot to fit. Are you going to give them a try?
Sorry that you lost your Rambo. I never did like the concept of non replaceable parts on these cards. I know the Ramps would not have changed anything in this case but at least you can change motor drivers.

Carl

I don't have time to investigate these now unfortunately. I was thinking this would be a better alternative for the hot end temp reading. The thermistors, although quite precise, are problematic from a mechanical connection perspective.

mhackney wrote:I don't have time to investigate these now unfortunately. I was thinking this would be a better alternative for the hot end temp reading. The thermistors, although quite precise, are problematic from a mechanical connection perspective.

I will order 3 of these because I also don't like the way the thermistors presently mount. One heater cartridge on one side and the thermistor cartridge on the other. It will take 2 -3 weeks though from China.
Once I get them I'll send you one because I need you to try them out and come up with the custom table for repetier and share it with me. ( tough crowd )

Carl

The cartridge heater and cartridge thermistor look to be an excellent combination. Maybe we could convince SeeMeCNC to produce a new heater block section that would allow these to be properly fitted without the aluminum foil kludge. I'd buy a few! (After some other knowledgeable person crafts the new tables! )

g.

Thanks Carl. I know how to build a calibration table for these. I contacted the vendor to get specs but there are none. These devices have 2 wires so they should be easy enough to integrate. I looked for a shorter 10mm - 20mm version of these but haven't found them as yet.

I have to say that I am very happy with my cartridge heaters. I have 20 of them now! Am considering offering the extras for sale.

mhackney wrote:Thanks Carl. I know how to build a calibration table for these. I contacted the vendor to get specs but there are none. These devices have 2 wires so they should be easy enough to integrate. I looked for a shorter 10mm - 20mm version of these but haven't found them as yet.

I have to say that I am very happy with my cartridge heaters. I have 20 of them now! Am considering offering the extras for sale.

Put the extras on your site. Be sure to keep some spares though, the past day or so proves you will need a few.

Well, I have the RAMPS 1.4 connected and started with a fresh Repetier host download from Git, I configured it from scratch for the MAX. I started with end stops and got those working, now I have motor control and the steppers sound smooth. The RAMPS supports 16 micro steps and came preconfigured that way. Now I just need to hook up the hot end and heated bed.

One thing about RAMPS - the connectors do not lock. I'm using the RAMBo connectors and they fit the RAMPS locations. But they pull out very easily. I need to decide if this is going to be my permanent solution or if I'll replace the RAMBo if I can't repair it. I'm also not happy with the connectors I assembled for the Rambo, there seems to be some fraying where the wire attaches to the crimp connector - probably from opening and closing the door the RAMBo was attached to too many times! You can see that here (attached to RAMPS):

[img]http://mhackney.zenfolio.com/img/s9/v87 ... 5524-4.jpg[/img]

Whatever I do, I will mount the board to a stationary location but make sure it can easily be removed for access.

I did get a nice wiring harness kit with the RAMPS that has the connectors professionally attached. I just don't relish re-wiring everything! The RAMPS does support dual extruders and RichRap has a cool mod to support 3 extruders. I also got these pre-assembled for $100 (bought 2) so they are pretty cost effective.

do you use the right size crimper for those connector pins. they shouldn't look like that if you did. But I assume you prolly used what you had available

the purpose of the back end of the connector pin is to crimp down the insulation too and provide some strain relief. The middle part of the pin is actually where the bare wire gets crimped. If you have the correct tool, it does this in one shot.

Been collaborating in the background with Carl (aka Eaglezsoar) on a leveling build plate. The basic idea is to have a 3 point attachment to the Rostock base so the plate itself can be leveled accurately. Then, with the plate made from MIC-6 aluminum, flatness is all but guaranteed. The heating element - Onyx or even a silicone heater - is mounted underneath. Since the Mic-6 is 5/16" thick, the Onyx can be secured with screws into tapped holes in the plate. These are outside the build area. An optional support brace could be installed to minimize warping/sagging of the Onyx. Silicone adhesive could also be used to secure it or a silicone heater.

[img]http://mhackney.zenfolio.com/img/s2/v72 ... 4084-4.jpg[/img]

I made the threaded posts from M10x1 bolts. I've machined the heads flat and drilled and tapped for the #6-32 screw that will attach the MIC-6 plate to it. Since the pitch is 1mm per turn, precise and predictable adjustments can be made. I'll likely put washers between the nuts and Rostock base.

The only question is heat-up time. Thicker aluminum means more mass to heat. More mass means either more time or more power. We'll see, we'll see...

my 3/8" mic 6 plate will be here to test out by this weekend, i'm hopeful this will solve some warping issues but looking around on other forums, Mic6 can also warp if not heated evenly. This only seems to be the case at higher temperatures though, nothing that we will be using for 3d printing so crossing my fingers.

Just arrived via Priority Mail:
[img]http://mhackney.zenfolio.com/img/s2/v72 ... 4568-3.jpg[/img]

The cylinders are grade N52 - big boy magnets - 9.86 pound pull force (as compared to the lesser N42 at 7.96 pounds for the same size magnet). These are 3/8" D by 3/8" long. The steel bearings are not magnetized, 3/8" diameter. After reading specs on commercial units and doing some force calculations, these should do the trick. I am going the way the commercial units are made with a cylindrical magnet and a steel sphere for a number of reasons. I milled a quick "sheath" in Delrin to test the joint and it is smooth as silk and stays perfectly centered. I should have something to show over the weekend.

Yeah I was thinking of something similar but it was expensive. http://www.ebay.com/itm/5-X-Magnetic-Ba ... 35c26fa972

I am looking forward to seeing what you come up with.

Yes, the pre-made units are pricy and may not be the best size for this application. The Delrin will make a great low friction bearing surface and be easy to machine and light weight. One of my friends called me "Dr. Delrin" last weekend because I constantly promote the virtues of the material! I use it a lot in my reels too.