Hi. I am new to reprap and just 2 days ago finished building my prusa mendel. I am having 2 issues that are stopping me from printing anything: 1. The softwares disconects from my printer when I am trying to move a motor, sometimes is the 1st click to move 10mm and sometimes it moves all motors ok but when I sent a model for dry run it does some movement and stops. I am not able to do even a 1x1x1cm cube dry run print all the way to the end. If I unplug say the Z motors it seems to do the job. 2. I also cannot get the Heater to work. When I try to turn the Heat On the red LED flashes and the printer disconnects. Any suggestions? This are my specs at the moment: * Prusa Mendel * Generation 6 Elec. * Latest Repetier firmware and Host for MAC (0.16) * Z motors wired on parallel * Baudrate 250000 Thanks in advance. F. https://reprap.org/forum/read.php?267,131229,131229#msg-131229 Tue, 06 Oct 2026 21:26:15 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?267,131229,131468#msg-131468 https://reprap.org/forum/read.php?267,131229,131468#msg-131468 nophead Repetier Sat, 05 May 2012 06:48:39 -0400 https://reprap.org/forum/read.php?267,131229,131456#msg-131456 https://reprap.org/forum/read.php?267,131229,131456#msg-131456 F.]]> Fabiano Repetier Sat, 05 May 2012 04:44:17 -0400 https://reprap.org/forum/read.php?267,131229,131450#msg-131450 https://reprap.org/forum/read.php?267,131229,131450#msg-131450 nophead Repetier Sat, 05 May 2012 04:17:35 -0400 https://reprap.org/forum/read.php?267,131229,131440#msg-131440 https://reprap.org/forum/read.php?267,131229,131440#msg-131440 Its hard to figure things out when you never even seen the machine in person.

After all it was just a question of wiring back inside the PSU. The dummy is not required to run the machine (at least in my case), but it helped me get to the problem and learn a few more things about how all of this works.

Now I need to work on the extruder block to get the thing to ready the desired temperature.
Thanks again everyone.

Case closed.
F.]]> Fabiano Repetier Sat, 05 May 2012 00:41:17 -0400 https://reprap.org/forum/read.php?267,131229,131426#msg-131426 https://reprap.org/forum/read.php?267,131229,131426#msg-131426
The heater resistor should be inserted into a heater block in a way that makes good thermal contact. If you simply had a naked resistor it would smoke and burn because it is severely overloaded. It works in the heater block because that acts as a heatsink greatly increasing its power handling ability. Also is must be a vitreous enamel resistor which are able to withstand 350C. Any other type will burn.]]> nophead Repetier Fri, 04 May 2012 20:08:13 -0400 https://reprap.org/forum/read.php?267,131229,131381#msg-131381 https://reprap.org/forum/read.php?267,131229,131381#msg-131381
I just managed to fix the pulsing light and I was able to turn the 6.8Ohms Extruder Heater.
I did a quick run (without filament) but with all motors on and the result was good....well, sort of.

The Heat Resistor immediately starting to smoke and turn black.
Is it something to do with the power supply of is my wiring wrong, etc...

Thanks again.
F.]]> Fabiano Repetier Fri, 04 May 2012 15:45:44 -0400 https://reprap.org/forum/read.php?267,131229,131374#msg-131374 https://reprap.org/forum/read.php?267,131229,131374#msg-131374
After insulting myself and the power supply several times I did the dummy connections on the red/black yellow/black cables using a 12V car lamp.

The weird thing is, and probably the one and only problem after all, it that both lamps are pulsing.
I saw in another post someone with the exact same problem and nophead said something about connection red to black wires, etc. Again, I am not very wise on eletronics and learn better by looking at something.

The way I set up my ATX is that I plug the green and grey wires on the switch at the back so that I have an external power on button. Don't know if this is the problem. If so could you please advise? Here are some pics.

Dummy
Connection

Thanks again.
F.]]> Fabiano Repetier Fri, 04 May 2012 15:08:42 -0400 https://reprap.org/forum/read.php?267,131229,131370#msg-131370 https://reprap.org/forum/read.php?267,131229,131370#msg-131370 nophead Repetier Fri, 04 May 2012 14:26:32 -0400 https://reprap.org/forum/read.php?267,131229,131344#msg-131344 https://reprap.org/forum/read.php?267,131229,131344#msg-131344
Five Stepper Motors (how high is the current adjust on each of the stepper drivers?)
Z-Stepper motors configured in firmware to remain powered when not moving draws more current
One Fan/Two Fans/No Fans - Some fans draw more currnt than others.
Any lights being used to pimp out the printer
Extruder (what is the heater resistor Ohm value?)

I would encourage you to find a larger capacity PSU. Having more Amps to work with eliminates any doubts, gives you more flexibility on adding options like the heated bed, and the bigger capacity may result in a longer time before PSU failure, although any PSU can fail at any time.]]> jcabrer Repetier Fri, 04 May 2012 10:00:15 -0400 https://reprap.org/forum/read.php?267,131229,131332#msg-131332 https://reprap.org/forum/read.php?267,131229,131332#msg-131332
You need a load on the 5V rail (red and black). Something like a 10R power resistor or a 12V car light bulb.

I would also shorten the 12V connections and use at least two black and two yellow wires. That is tricky though as it looks like the gen6 has an inadequate power connector. I would replace that with screw terminals.

USB is not very tolerant to ground noise in my experience despite being differential signals.]]> nophead Repetier Fri, 04 May 2012 06:47:48 -0400 https://reprap.org/forum/read.php?267,131229,131327#msg-131327 https://reprap.org/forum/read.php?267,131229,131327#msg-131327 -------------------------------------------------------
> Repetier.
>
> Ok I will try that and give you a reply in a few
> hours...
>
> One more thing before I go. IF the problem is the
> Amps what If I take X, Y and Z motors and the
> OPTOS, leaving just the Extruder Parts connected
> to the board, my 10A@12V should be able to run the
> Heater. Correct?
>
Yes.
> I just tried that and it does the same thing LED 3
> Flashes once and Conneciton Lost.
>
Well if nopheads comment fits on your ATX like the othe 99% this was to expect. I think what the ATX does is it gives you very little power for some standby operations. As soon as you need more power it wants the basic load. You should also look into the reprap wiki. There is a longer article on connecting atx to printer boards.]]> repetier Repetier Fri, 04 May 2012 05:57:16 -0400 https://reprap.org/forum/read.php?267,131229,131325#msg-131325 https://reprap.org/forum/read.php?267,131229,131325#msg-131325
Ok I will try that and give you a reply in a few hours...

One more thing before I go. IF the problem is the Amps what If I take X, Y and Z motors and the OPTOS, leaving just the Extruder Parts connected to the board, my 10A@12V should be able to run the Heater. Correct?

I just tried that and it does the same thing LED 3 Flashes once and Conneciton Lost.

Thanks in advance again.
F.]]> Fabiano Repetier Fri, 04 May 2012 05:50:57 -0400 https://reprap.org/forum/read.php?267,131229,131319#msg-131319 https://reprap.org/forum/read.php?267,131229,131319#msg-131319 repetier Repetier Fri, 04 May 2012 05:07:25 -0400 https://reprap.org/forum/read.php?267,131229,131318#msg-131318 https://reprap.org/forum/read.php?267,131229,131318#msg-131318
Bingo. Re-wired and its working.

Thanks again.
F.]]> Fabiano Repetier Fri, 04 May 2012 05:07:21 -0400 https://reprap.org/forum/read.php?267,131229,131315#msg-131315 https://reprap.org/forum/read.php?267,131229,131315#msg-131315 repetier Repetier Fri, 04 May 2012 04:57:58 -0400 https://reprap.org/forum/read.php?267,131229,131313#msg-131313 https://reprap.org/forum/read.php?267,131229,131313#msg-131313
I am not very knowledgeable on electronics, so I didn't quite get your reply...sorry.
My PSU is connected to the Gen6 via a single set of yellow/black wires. Nothing else is attached to it.

Here is an IMAGE of the ATX-Gen6 connection

Any advise is appreciated.
F.]]> Fabiano Repetier Fri, 04 May 2012 04:56:09 -0400 https://reprap.org/forum/read.php?267,131229,131311#msg-131311 https://reprap.org/forum/read.php?267,131229,131311#msg-131311
I just changed the Extruder_Speed from 20.0 to 18.0 and to 10.0 and it does the exact same movement. I have uploaded a video of the problem. Notice how the extruder kind of moves forward and then backwards when I hit Extrude:

Extruder Problem (MOV)

Also about the Amps on the ATX. It says 10A for the +12V, everything else is lower then this value.

Currently I do not have a Heated Bed attached to the power supply, so its just 3 OPTOS, 5 NEMA-17 Motors, Thermistor and Heat Resistor...

Thanks again.
F.]]> Fabiano Repetier Fri, 04 May 2012 04:50:14 -0400 https://reprap.org/forum/read.php?267,131229,131304#msg-131304 https://reprap.org/forum/read.php?267,131229,131304#msg-131304
Another thing it could be is a poor ground connection between the board and the power supply. It should be short and thick. If not motor and heater current can flow though the USB cable ground and that can disrupt the comms. Because USB is a connection oriented protocol it will not recover from a lost connection without host intervention.]]> nophead Repetier Fri, 04 May 2012 03:54:33 -0400 https://reprap.org/forum/read.php?267,131229,131297#msg-131297 https://reprap.org/forum/read.php?267,131229,131297#msg-131297 -------------------------------------------------------
> Repetier.
>
> After trying your suggestions this is the
> outcome:
>
> Dry Run with NO motors connected:
> I did 5 runs and it worked 100% of the time.
>

So the cable is ok and it is no software problem as far as it depends on motors.

> Dry Run with ONLY the X, Y and Z motors
> connected:
> It did not work at first, same problem as before
> (connection closed).

The firmware runs the same code but the load causes the problem.

> Then I found something out if I run the motors
> once, even 0.1mm, just to switch them on then turn
> them off and press FAKE OK, I can make then work
> without any errors. I did 10 consecutive runs and
> they all worked.
That is strange. Fake OK assumes the ok was send signaling a command was received. This has absolutely no effect on the firmware. It is to compensate a lost OK from the firmware. Perhaps enabling the motor causes a voltage drop enough to cause communication problems but not enough for a connection lost. Thats the only thing that makes sense to me.
>
> Dry Run with everything plugged in:
> Same as before. It fails if I just switch the
> board on and run the job without pressing FAKE OK
> before.
>
> Run with no filament and with a very small LED
> Resistor (temp. for run set at 15 degrees
> Celsius):
> X, Y and Z engines working and the Extruder engine
> makes more noise than it actually turns. Need to
> hit the FAKE OK before run again.
>
> Run with no filament and with the 6.8Ohms
> Resistor:
> Red light on the Gen 6 board flashes once and I
> get a "1 Commands waiting" at the bottom parts of
> the window. The printer stays as connected at the
> host software but I cannot give it any more orders
> and I need to close the connection and reconnect.
>
>
> So it looks like either the Resistor its drainning
> all the power from the power supply and shutting
> down the board or my connection to resistor is not
> done properly.
> Furthermore the Extruder motor seems to be very
> moody and sometimes it works wonder and sometime
> it just makes noises but does not rotate...power
> supply again?
> JCabrer pointed out I need a 12V with at least
> 18Amps as a power supply. I will try to find one
> tomorrow and give it a go.
>
> F.
The sounds from your extrude rmotor are lost steps. Either because you have filament inserted with only 15 degrees celsius, the motor blocks or

#define EXTRUDER_SPEED 18

is set to high. My maximum is 18. I'm working on an update where acceleration is used, so extruder speed can be increased. But for now reduce it until your motor doesn't lose steps any more.

Ams needed is not that high if you have no heated bed connected. With 6.8 Ohm for heater you need at maximum 12/6.8+4*1.5=7.8A Round it up to 8A you need 10*12 = 96W on the 12V voltage line. Look at the specs of your ATX. The 200W is for all voltages so the chance is high 12V delivers less then this. With heated bed on 12V you come fast to the 18A JCabrer told you. And with ATX power look which wire can deliver how much current. Not sure how the atx really works, but you may need to combine the power lines to get full power if they are created in separate parts of the supply.]]> repetier Repetier Fri, 04 May 2012 03:09:27 -0400 https://reprap.org/forum/read.php?267,131229,131275#msg-131275 https://reprap.org/forum/read.php?267,131229,131275#msg-131275
After trying your suggestions this is the outcome:

Dry Run with NO motors connected:
I did 5 runs and it worked 100% of the time.

Dry Run with ONLY the X, Y and Z motors connected:
It did not work at first, same problem as before (connection closed).
Then I found something out if I run the motors once, even 0.1mm, just to switch them on then turn them off and press FAKE OK, I can make then work without any errors. I did 10 consecutive runs and they all worked.

Dry Run with everything plugged in:
Same as before. It fails if I just switch the board on and run the job without pressing FAKE OK before.

Run with no filament and with a very small LED Resistor (temp. for run set at 15 degrees Celsius):
X, Y and Z engines working and the Extruder engine makes more noise than it actually turns. Need to hit the FAKE OK before run again.

Run with no filament and with the 6.8Ohms Resistor:
Red light on the Gen 6 board flashes once and I get a "1 Commands waiting" at the bottom parts of the window. The printer stays as connected at the host software but I cannot give it any more orders and I need to close the connection and reconnect.


So it looks like either the Resistor its drainning all the power from the power supply and shutting down the board or my connection to resistor is not done properly.
Furthermore the Extruder motor seems to be very moody and sometimes it works wonder and sometime it just makes noises but does not rotate...power supply again?
JCabrer pointed out I need a 12V with at least 18Amps as a power supply. I will try to find one tomorrow and give it a go.

F.]]> Fabiano Repetier Thu, 03 May 2012 20:04:27 -0400 https://reprap.org/forum/read.php?267,131229,131271#msg-131271 https://reprap.org/forum/read.php?267,131229,131271#msg-131271
My power supply is 12V but max of 10Amps and my Extruder Heat and Thermistor are these?
Extruder Heat
Thermistor

I am currently doing some tests and I will give a feedback in 30min or so.
Thanks.
F.]]> Fabiano Repetier Thu, 03 May 2012 19:10:36 -0400 https://reprap.org/forum/read.php?267,131229,131270#msg-131270 https://reprap.org/forum/read.php?267,131229,131270#msg-131270
200 Watts seems very low. Can you tell us what the 12V amps rating is on the supply? It should be on the label somewhere.

If you have less that 18 Amps@12V, you might run in to trouble because the power supply voltage will collapse.

Also, if your hot end has a short, or the resistance is really low (say less than 5 Ohm) you will draw more amps than the supply can sustain.

If you want to play it safe, get a used supply with at least 23 Amps, or buy one of the PSU that Lulzbot.com sells.

-Wildseyed-]]> jcabrer Repetier Thu, 03 May 2012 18:54:20 -0400 https://reprap.org/forum/read.php?267,131229,131265#msg-131265 https://reprap.org/forum/read.php?267,131229,131265#msg-131265
You could try adding a fan or some other load on 12v. Some Atx supplies need a basic load or they will turn off. Could also be your problem, but i think you have simly connected the 12v to the board? Should be enough load to keep it on.

Regarding your log, i saw a real disconnect. I think the FTDI chip really closed the connection. With stable voltage this normally neverh apens. Even with a reset on the board you don't get a disconnect. So the connection itself could also be the problem. So some other tests you cold do

1. Unplug motors and do a dry run
2. Use a different USB cable.]]> repetier Repetier Thu, 03 May 2012 17:32:35 -0400 https://reprap.org/forum/read.php?267,131229,131255#msg-131255 https://reprap.org/forum/read.php?267,131229,131255#msg-131255
I have a felling is a power shortage as well, but I cannot figure it out.
My power supply is a brand new ATX 200W and the voltage is 12V solid.
Also all the TP1, TP2, TP3 and TP4 little dials on the board are all set on the middle.

Do you think I could increase the power input above 12V?

Also I have attached a Log file of my last run, don't know if can be of any help.
F.]]> Fabiano Repetier Thu, 03 May 2012 16:23:56 -0400 https://reprap.org/forum/read.php?267,131229,131247#msg-131247 https://reprap.org/forum/read.php?267,131229,131247#msg-131247
From your description I guess your power connection is not stable. Every time you draw more current you seem to loose connection. You should have a closer look at the log output. If you see a start after your connection loss, the hardware did a reset for some reason. That normally
happens if your voltage goes below a certain treshhold.]]> repetier Repetier Thu, 03 May 2012 15:39:56 -0400 https://reprap.org/forum/read.php?267,131229,131229#msg-131229 https://reprap.org/forum/read.php?267,131229,131229#msg-131229
I am new to reprap and just 2 days ago finished building my prusa mendel.

I am having 2 issues that are stopping me from printing anything:

1. The softwares disconects from my printer when I am trying to move a motor, sometimes is the 1st click to move 10mm and sometimes it moves all motors ok but when I sent a model for dry run it does some movement and stops. I am not able to do even a 1x1x1cm cube dry run print all the way to the end. If I unplug say the Z motors it seems to do the job.

2. I also cannot get the Heater to work. When I try to turn the Heat On the red LED flashes and the printer disconnects.

Any suggestions?

This are my specs at the moment:
* Prusa Mendel
* Generation 6 Elec.
* Latest Repetier firmware and Host for MAC (0.16)
* Z motors wired on parallel
* Baudrate 250000

Thanks in advance.
F.]]> Fabiano Repetier Thu, 03 May 2012 14:02:53 -0400