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Quieting the ESP120 Fans

As mentioned in the main ESP120 article, you can slow down the fans in the ESP120. This will reduce the noise from unbearable to near silent.

Pictures work best but basically, you locate the 4 fan leads, and insert 15Ω resistors in series with the 4 red fan wires. Again, since the ESP120 does not use PWM fans, this works and the ESP120 does not go into standby mode.

The ESP120 still runs at basically ambient temp. In future experiments, I plan to gut a ESP120, move it into a larger enclosure and eliminate the fans altogether.

 

Each fan had 234mA running through them. So I chose 15 ohm , 1W resistors. Maybe a tick small but the slower the fans run, the less current they draw and the resistors were running cold.

 

Here are the 4 fan leads, cut and tinned.

 

Resistors soldered inline with heat shrink ready to go.

 

All done and heat shrinked.

 

Comments

15 responses to “Quieting the ESP120 Fans”

  1. Michael Martin Avatar
    Michael Martin

    Mine had Ball Bearing fans that sounded like the balls were not round anymore. My supply ran the fans at about 8 Volts at low current output. I added the 15 Ohm resistors but they were still obnoxious.
    I finally found four Sleeve Bearing fans on eBay.
    Using lower output fans, I figuring my duty cycle needs would be far less than the rated current of the supply.
    The supply is quiet as a mouse now. Taking it out of the case may be an option as well.

    Great data on all your tabs Rob !!

    Reply
    1. N4GA - Rob Avatar
      N4GA – Rob

      Thanks Mike!

      Reply
  2. Hugh Coleman Avatar
    Hugh Coleman

    I plan to move mine in the next room 😛 when I ran a pair it was honorable.
    Hugh AE5VB

    Reply
    1. N4GA - Rob Avatar
      N4GA – Rob

      That would be great!

      Reply
  3. Tom Evans KI8K Avatar
    Tom Evans KI8K

    ROB
    On your “recommendation” I got hold of a HP ESP120 🙂 for my w6pql LDMOS SSPA. Like you said even at 1KW the thing is solid as a rock.
    My only issue is (almost embarrassed to say this) I can’t figure out how to get into the chassis to do the fan quieting trick :-(…..
    I’ve looked at your photos beginning to end and they seem to indicate that the top and one side hinge open as a unit??? Nevertheless even with the ESP fresh out of the box on my workbench I could decipher it — bummer.
    Would you be good enough to give me a hint of two pse?
    Thanks
    TOM EVANS KI8K

    Reply
    1. N4GA - Rob Avatar
      N4GA – Rob

      Sent you a email Tom. Hopefully you got in.

      Reply
  4. Andre Avatar
    Andre

    Hi, just replaced the Fans with Noctua, so it is silent now.
    Can you answer me a question please?:
    – If i run the ESP120 without having anything switched on it uses about 80W, is this normal?
    – i also recognized, one heatthink (with now no load getting really hot). Don´t know if this changed if i put some load at the output.

    Reply
    1. N4GA - Rob Avatar
      N4GA – Rob

      Andre,

      I’ve never measured the idle power but 80W is probably normal.

      Yes, on all mine, one of the two heat sinks gets hot under no load.

      My original plan was to put the PCBs in a larger enclosure and use no fans at all. But when I realized how hot that one heat sink runs open air, with no fan, I figured that was not really possible.

      Can you share the part number of your Noctua fans?

      Thanks & 73

      Reply
  5. Chris WB2VVV Avatar
    Chris WB2VVV

    Thank You for sharing this information Rob!

    I have had an HP ESP120 sitting on my shelf for quite some time as I was initially put off by the connections, and lack of connection documentation. Well, thanks to your info I was able to both turn mine on, and to also make it QUIET by adding 4 resistors as you suggested. The casework has quite sharp inside edges, which the two nicks on my hands are reminding me of. Anyway, I soldered heavy pigtail leads to the push-in connecters and ran the pigtails to a beefy screw terminal block I epoxied to the top of the casework. I removed the plastic louvers and pull-out lever to give a better view of the LEDs and the metal fan intake screens. Removing the plastic louvers exposes a plate that extends with 2 screw holes to mount my galvanized electrical box and double pole 240 VAC power toggle switch. Amazing that they used a 2 X 2 push-push fan architecture to blow a lot of air! I never heard it full on but I have to think that was some bodacious noise! Your 15 ohm voltage drop resistor recommendation is perfect as it allows a reasonable airflow to remain, while balancing the need for QUIET fans commensurate with ham radio analog duty cycles. I have temporarily set it aside waiting for me to finish an LDMOS deck that’s on my bench.

    https://flic.kr/p/2nDC4Et

    I am currently using a MEAN WELL SE-1500-48 to power a 4 X SD2943 MOSFET 160m thru 6m deck as that power supply had easy and rugged screw terminal connections, but its fans are very loud – so much so that back when completing that amp deck a number of years ago I had to install a noise gate in my microphone line for SSB. Not a problem for CW though. I need to take that power supply apart now that it is long out of warranty, and reduce its fan speed too.

    73, Chris WB2VVV

    Reply
    1. N4GA - Rob Avatar
      N4GA – Rob

      Thats good Chris, thanks for the comment!

      I did pretty much the same with the toggle switch but didn’t mount it right to the case like you.

      I originally planned to take it all apart and mount it into a more presentable box, with NO fans, but as you know, this would be quite the task!

      Also, I’ve gotten used to it’s form factor and I slide it right into a bookcase and it takes near zero space. So, I’m just gonna leave it like that.

      Reply
  6. Sid Avatar
    Sid

    Wired mine up today +51.8V no load.
    Still too loud with the 15 ohm resistors in line with the fans.
    I’ve ordered a DC-DC converter from EBay to power them.
    One thing I shall check later is to see what the internal supply voltage is and also get the size of the fans to see if I can get quieter replacements.

    Reply
    1. N4GA - Rob Avatar
      N4GA – Rob

      Some people have put nocturna brand fans in it. They say they can’t hear them.

      Reply
  7. Mark Avatar
    Mark

    I have been working on a kit amplifier, so the ESP120 noise was not bad… only on for brief testing periods. I have finally gotten far enough on the amp that the noise from the power supply was enough to annoy me. Bought the 15 ohm 1 W resistors. They arrived today. Cracked the box open.

    Sad to say, someone already did the modification on my supply. UGH!

    Still, it is quite noisy. I am guessing the bearings in the fan are near end of life.

    I wonder if you could share the part number of the Noctua (or Nocturna) fans that Andre put in.

    (by the way, thanks much for all the good information on this device. Very helpful)

    Reply
    1. N4GA - Rob Avatar
      N4GA – Rob

      Aww man, what a bummer!

      I’d be happy to share the fan PN with you if I had it!

      I bet you could figure it out here: https://noctua.at/en/products/fan

      Sorry I don’t have the info.

      73

      Reply
    2. Marl Avatar
      Marl

      Closest match I can find is https://noctua.at/en/nf-a6x25-flx/specification, but it is only 17 CFM, versus 32 CFM for the Nidec that is in mine now. Of course, you have already said that for an amateur radio application, the airflow of the stock fans is way overkill.

      That said, the sound is WAY less with this fan… 19 dBA, versus 43 for the Nidec.

      But I really would like to know if you know the part number that Andre is using.

      Reply

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