Taz 3 - Control Box Fan Noise Fix?

I just bought a refurb Taz 3 and am very pleased with it other than the horrendous electrical noise coming from the control box fan. To be clear, the noise isn’t from the movement of the fan blades pushing air. If I stop the fans from moving with my finger, I still hear the noise.

I suspect it’s from the Rambo (version 1.2f BTW) using PWM to control the fan speed. Is there a fix for this? I wouldn’t mind just having it run at 100% all the time. I swapped in different fans and they all have the same noise.

Does the Rambo 1.3 have this same “problem”?

I don’t think it’s related to the board. Which Firmware Version do you use? I will have a look into configuration.h then…

Running Marlin 2014Q2

Here’s the output when I hook up to the printer with the Arduino IDE:

start
echo: External Reset
Marlin 1.0.0
echo: Last Updated: MendelMax_2-0_RAMBo_1-2e_GLCD_v1_24V on Feb 27 2015 18:00:38 | Author: LulzBot
Compiled: Feb 27 2015
echo: Free Memory: 3373 PlannerBufferBytes: 1232
echo:Stored settings retrieved
echo:Steps per unit:
echo: M92 X100.50 Y100.50 Z800.00 E853.90
echo:Maximum feedrates (mm/s):
echo: M203 X800.00 Y800.00 Z3.00 E50.00
echo:Maximum Acceleration (mm/s2):
echo: M201 X9000 Y9000 Z100 E10000
echo:Acceleration: S=acceleration, T=retract acceleration
echo: M204 S1800.00 T3000.00
echo:Advanced variables: S=Min feedrate (mm/s), T=Min travel feedrate (mm/s), B=minimum segment time (ms), X=maximum XY jerk (mm/s), Z=maximum Z jerk (mm/s), E=maximum E jerk (mm/s)
echo: M205 S0.00 T0.00 B20000 X8.00 Z0.40 E10.00
echo:Home offset (mm):
echo: M206 X0.00 Y0.00 Z0.00
echo:PID settings:
echo: M301 P34.00 I4.00 D113.00
echo:SD init fail

Connector X30 on the RAMBo has a constant supply voltage on it. Yes, you are hearing the PWM, the fan does not really like having its supply voltage modulated. You will need to make sure you plug the fan on to the connector the correct polarity. Plus the fan will now run full speed(a lot faster than it runs on the PWM control) which tends to become VERY loud sounding after a short while. If that becomes an issue you can always search for a quieter fan replacement.

I don’t have an oscilloscope, so I can’t verify the frequency of the PWM, but I’m measuring the voltage at fan2 at ~6.3V.

I’m working on looking through the configuration.h firmware to see if there is a place to disable PWM to the fan2 header.

First, it’s absolutely not neccesary that your hear the PWM. It’s only a question of frequency, also Marlin has options to play with that.
In the Rambo changelog, I couldn’t find anything that seems to be related to Fan PWM noise, and I have zero noise on my TAZ 5 so I did a comaprison.
The only difference semms to be #define FAST_PWM_FAN is enabled on TAZ 3, not on TAZ 5. I would try to disable this, and flash it.

You can also try to set the Fan speed to 255 (full speed), maybe this also disables PWM. Default is 100. But I would try the #define statement first.

Had some luck with modifying the firmware, though commenting out the “#define FAST_PWM_FAN” had no effect.

I went into the Marlin_main.cpp file and changed the following section to make the fan run at full speed all the time. I measured 12v off the pins, but still has a very loud electronic whine. If this is the way Taz printers run, then so be it, but it seems like there is something wrong and it shouldn’t be making so much noise.

void caseFan()
{
if ((millis() - lastMotorCheck) >= 2500) //Not a time critical function, so we only check every 2500ms
{
lastMotorCheck = millis();

if(!READ(X_ENABLE_PIN) || !READ(Y_ENABLE_PIN) || !READ(Z_ENABLE_PIN)
#if EXTRUDERS > 2
|| !READ(E2_ENABLE_PIN)
#endif
#if EXTRUDER > 1
|| !READ(E1_ENABLE_PIN)
#endif
|| !READ(E0_ENABLE_PIN)) //If any of the drivers are enabled…
{
lastMotor = millis(); //… set time to NOW so the fan will turn on
}

if ((millis() - lastMotor) >= (CASEFAN_SECS*1000UL) || lastMotor == 0) //If the last time any driver was enabled, is longer since than CASEFAN_SEC…
{
if (CASEFAN_SPEED_IDLE >= CASEFAN_SPEED_MIN)
{
digitalWrite(CASEFAN_PIN, CASEFAN_SPEED_IDLE);
analogWrite(CASEFAN_PIN, CASEFAN_SPEED_IDLE);
}
else
{
digitalWrite(CASEFAN_PIN, CASEFAN_SPEED_MIN);
analogWrite(CASEFAN_PIN, CASEFAN_SPEED_MIN);
}
}
else
{
if (CASEFAN_SPEED_FULL <= CASEFAN_SPEED_MAX)
{
digitalWrite(CASEFAN_PIN, CASEFAN_SPEED_FULL);
analogWrite(CASEFAN_PIN, CASEFAN_SPEED_FULL);
}
else
{
digitalWrite(CASEFAN_PIN, CASEFAN_SPEED_MAX);
analogWrite(CASEFAN_PIN, CASEFAN_SPEED_MAX);
}
}
}
}
#endif

For what its worth, my modified taz 3 with stock fan doesn’t have any PWM noise, nor has it ever on any of the firmware revisions it has been on. You may have a component starting to go bad in there. I am usually able to hear that high pitch pretty well, so if it was there I don’t think I am missing it.

I took a video. Trying to figure out how to post it. I appreciate the help. It’s otherwise a nice machine and is working really well.

Upload the video to youtube, then you can embed it here. Check out my anti wobble thread in the developer section of the forum for the posting syntax if you need it (reply to post, copy code, hit cancel, etc.)

Hers a link to a YouTube video of the fan in action.

https://youtu.be/aXulMpucYt0

(can’t figure out how to embed the youtube video)

Yeah, that’s not normal.

So my guess is that it’s either a bad RAMBo board or PSU.

I don’t think it’s anything I can fix with my current knowledge base and skill set, unfortunately.

I’ll have to call i-t-w.com on Monday and see about getting a new board.

Well, no significant improvement after replacing the RAMBO board. I can’t believe this fan would be this noisy just due to PWM. I really like the printer, but the noise is driving me crazy.

Did you try a different fan? That one might have a partial short?

I’ve tried a couple other fans I have, though they are 12v only. Same noise.

The C.B. Fan is a 24 volt fan, if you use a 12 volt fan you will get LOTS of PWM noise or possibly no fan movement at all. I tend to change out the 12 volt fans for 24 volt fans to prevent possible fires if the fan over heats from the double supplied voltage being feeded to it during extended unattended printing sessions.

My brand new TAZ 5 does exactly the same thing. Using a PWM frequency of 500 Hz is just begging for trouble. Plus the fan is not designed for this, so it might lead to premature failure too.

This is not the worst PWM design sin in the TAZ either. The heated bed chop frequency is so low (just a few Hz) that it’s very hard on the power supply. Even though my TAZ has the new improved PSU model (MeanWell), it’s not designed for this kind of abuse. Not sure how to fix it; I guess if it survives a year (the warranty period), it’ll be fine.

Ok, back to the fan - A quick fix for the noisy fan noise problem is a simple filter network to smooth the PWM square wave going to the fan. Splice a 100 Ohm power resister (10W) into one of the fan power supply wires, followed by a 100 uF capacitor (50V) across the fan. This eliminated the fan noise in my TAZ 5 and the fan speed is about the same as before.

My Taz 5 has done this since day one, I just now verified and it sounds exactly like yours.