Temp Undefined, possible broken heater for HE280

[Brodensears]

When trying to heat up both the nozzle and the bed on our labs Rostock Max v3, there are a couple errors.
1. Our hot bed won't get above 82, and even with a cloth on top, not much more than that. I read that it should get up to 100 C, but that doesn't seem possible currently. Is there a way to fix this?

2. When heating up the bed and nozzle, the bed will heat up for a little bit, but the nozzle stays constant. After a little bit, both the bed and the nozzle go Undefined. While reading on the forums, I tried the voltage across the fuse on the heater and the voltage going across while on is >12. Therefore, I thought the heater might be broken. Is this true? I thought it might be the thermister, but the heating block doesn't even get warm when it attempts to heat up.

Anything helps! Thanks

[geneb]

Check the terminal blocks on the RAMBo to make sure you don't have any "cooked" terminals. When you turn the hot end on, check the hot end terminals on the RAMBo to make sure you see 12v there as it heats up.

If you've got a v3 with the single-rail power supply (not ATX), you can bump the output voltage a bit using the adjustment pot next to the terminal block on the power supply. This might get your bed hotter.

g.

[rootboy]

I'm with Gene on this one, I'm going to say that you have a loose connection somewhere.


First off, the voltage check that you did on your your heater indicates a blown fuse. The classic way of testing for a blown fuse is to put a voltmeter across the fuse. If it shows voltage, in this case 12 volts, it's a goner.

"I tried the voltage across the fuse on the heater and the voltage going across while on is >12. "


But let's assume that's not the case for the moment. Here's a few suggestions.

1) Check the voltage at the bed and the nozzle. Not at the terminals on the board. This is the best indication of what voltage your heater is receiving. If it's under your source voltage by more than a volt, work your way backwards feeling for warm spots with the heater(s) on. Mind your fingers...

2) Has this been working? Is there a chance that you might be trying to run a 24 volt cartridge on 12 volts?

3) How do the MOSFETs look? Any sign that they have been cooked? Look around the MOSFETs for damaged or missing parts (having the gate fire intermittently would cause this). Did you hear something "pop" and then hear something ricochet recently? That would be an unauthorized chip launch...

4) Drive your heaters directly from your power supply (be sure to disconnect them from your board first otherwise you will most likely destroy the board). Do they get up to temp now? Don't leave them this way for any longer than you need to to see the temperatures on your heaters.

5) Do you have a scope? Putting a scope on the heaters will give you an idea as to what the duty cycle is. Short power pulses followed by long off times ain't going to heat things up much. By the same token, sporadic power pulses that come and go with long or intermittent idles times would tend to indicate that something is misfiring at the board level.

6) Try a different power supply for your Max V3.

[geneb]

...and do NOT test fuses in-circuit. Remove them first.

g.

[rootboy]

Meh, whatever.

Before I was a Controls engineer, I was a Colorado Master electrician. And that's how we did it.

[geneb]

Well with electronics like the RAMBo, you can get a false "good" check if you test it in circuit, so "meh" yourself.

g.

[Xenocrates]

Depends on if you go based on resistance or voltage, as well as your criteria for acceptable versus bad. It's pretty unlikely that you wouldn't have at least a volt of drop across a blown fuse, no matter what sort of leakage you got from other electronics, and anything beyond 100 mV at these low of voltages tells me that the fuse could probably use replaced, even if it isn't opening the circuit.

[rootboy]

Well yeah, if you have it off while you measure for voltage, it would be a display of a fundamental lack of electrical understanding.

And since one of the things that he is looking for is voltage drop, he's going to need volts and a load. And since he's getting some heat, it's obvious that the fuse would show good resistance-wise, so why check it in the first place?

For what not to do...

https://www.youtube.com/watch?v=TwIvUbOhcKE

[Brodensears]

Thank you all! I will look into this and get back as soon as posible

[Brodensears]

I see on the side of the heater there is a 115 and a 230, should I push it so that the 230 is available?

[Brodensears]

I'm not seeing a knob on the heater, where exactly can that be found?

[Brodensears]

Shouldn't the voltage across the fuse be normal unless it is blown at which point it should be 0 because it is now closed?

[Xenocrates]

If by heater, you mean the thing on the hotend that wires go into, there shouldn't be anything like that. If you're referring to a metal box with a bunch of wires, unless you live in Europe, or somewhere else with 230V power, no, don't flip the switch. In either case, take a picture of what you mean, to help clarify.

The voltage across the fuse should be 0, or close to it, unless it's blown. Fuses open the circuit when they blow, meaning that like shutting a valve, there's electricity on one side, and not the other, so when measuring the voltage (which is the difference in potential energy). This means that a bad fuse will have a higher voltage reading.

[Brodensears]

Thanks! I'll clarify...

On the power supply (atleast the metal box at the bottom) there is a 115 and 230. From where I read on earlier posts (and yours) I should have it at 115 which is its current setting.

For the fuse I also got the closed/open confused. If I am understanding correctly, do you mean to say that the open circuit will allow the voltage across the fuse when it blows (and therefore reach ~12)? Ah... I get it now, there should be no difference. Thanks!

[Brodensears]

So I should at least replace the fuse. On the metal box (the power supply I believe?) I am getting 12.36, how do I attach a picture (I'll look after I finish this post)

[Brodensears]

Here should be the image. I measured across the second from the left thick red wire and the thick black wire on the right

[Brodensears]

Will a blown fuse also be visible to the eye?

[Brodensears]

And I confirmed again, while trying to heat up the nozzle I get 12.1 V across the fuse and I also get 12.1 volts across the entire block by measuring from the two wires with the solder sticking out from the board

[Brodensears]

Also, when checking from the RAMBo I get 12.1 across the hot end terminals.

[Brodensears]

I guess last questions would be:
1. Where can I find the knob for adjusting the voltage to the bed heater?

2. Does this seem for sure the fuse as an issue?

[Xenocrates]

If you are indeed getting 12v across the fuse, then yes, it's an issue with the fuse. Fuses aren't always visibly blown, especially ceramic and thermal fuses. As for 1, well, if you look at your picture, the knob should be on the left side, underneath the V adjust

I think you're still confused a bit about the voltage drop though. Voltage does not have a universal zero. It's always relative to something. If the fuse is not blown, then the two sides are connected, and thus the difference between them is very small. This means a small voltage. If it's blown, then they are not connected, and the difference can be quite big. For other components, if you have a large voltage drop, and a high amperage, that means a lot of power is flowing. But a fuse does not allow any power to flow, because no amps are getting through, despite the voltage drop.

[rootboy]

So many questions...

"I see on the side of the heater there is a 115 and a 230, should I push it so that the 230 is available?"

Unless you live in an area where the voltage is 230 volts (Europe comes to mind), then no. That's to select your input voltage for your power supply, if you live in the states then keep it at 115. If you did slide it to 230 then it would most likely reduce your output voltage.


"I'm not seeing a knob on the heater, where exactly can that be found?"

There isn't one. You set the temperature by way of your interface (usually either the program that you use to run your printer, or from the LCD).


"Shouldn't the voltage across the fuse be normal unless it is blown at which point it should be 0 because it is now closed?"

"For the fuse I also got the closed/open confused. If I am understanding correctly, do you mean to say that the open circuit will allow the voltage across the fuse when it blows (and therefore reach ~12)? Ah... I get it now, there should be no difference. Thanks!

"So I should at least replace the fuse. On the metal box (the power supply I believe?) I am getting 12.36, how do I attach a picture (I'll look after I finish this post)"

"Will a blown fuse also be visible to the eye?"

Nope, you've got it backwards. A good fuse will have a few tenths of an ohm of resistance, and that multiplied by the current that is going through it creates a voltage drop across the fuse. Whatever that voltage drop ends up being will be robbed from the rest of the circuit, and won't be available for use elsewhere. But for a properly selected fuse, this is negligible.

A blown fuse will have infinite ohms of resistance, and therefore nearly all of the voltage drop will be across it. From your readings, the absolute max voltage drop across your fuse is about .25 volts (neglecting other drops in your circuit), that's perfectly fine.

Blown fuses are pretty obvious, ranging from blackened glass where the element should be, to brown goo on one end or both ends (usually indicating a bad fuse holder), to shrapnel when it blows to kingdom come (one of the ratings that we need to pay attention to is the symmetrical amps. 200,000 RMS symmetrical amps is usually a good number). Non-glass fuses usually require a meter to check out.


From reading further on in your posts, it appears that your fuse is working just fine, and you should leave it alone. Your 12.1 volt reading sounds normal to me.

At this point an easy check would be to tune your PIDs. Please try to include the output from the console while it is tuning if you can.

626Pilot explains it much better than I can, check out his post on the subject:

http://forum.seemecnc.com/viewtopic.php?t=11440

But I would do an auto-tune first to see if that helps. Here's a page on the process:

https://matterhackers.dozuki.com/Guide/PID+Tuning/6


Let us know how it works out.

[Brodensears]

I'll get back to you guys tomorrow (when I have access to it and can do these new tests), but thanks today for your help so far!

[rootboy]

NP. Next we need to look at your thermistors. But since both were going astray, I suspected a voltage drop problem.

And I'm still confused from your original post stating: "I tried the voltage across the fuse on the heater and the voltage going across while on is >12." Could you post a picture of how you are making this measurement when you test it please?

And I just took a close look at the photo that you posted in post #13, and the solder joint on the "-" terminal for your hotend heater sure looks wonky to me. Can you touch that up with a soldering iron and try it again please?