SB-220 fan "rattle" when turned on

Discussion in 'Amateur Radio Amplifiers' started by K2QI, May 20, 2020.

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  1. K2QI

    K2QI Ham Member QRZ Page

    Lately I've been noticing a rattling noise coming from my SB-220's cooling fan upon cold start. It's not a ticking, but a definite rattle which is quite unnerving. The weird thing is, it goes away after about 30 seconds. I'm guessing a bearing, sleeve, or bushing which houses the fan shaft warms up and via thermal expansion, whatever play goes away. It doesn't do it all the time and the fan generally remains quiet for hours except for the hum of the blades spinning.

    I haven't had my amp apart in a while. I can't recall if this unit had sealed bearings or one with oiler holes for the bearings. Either way, should I take this as a sign that it's time to replace the entire motor assembly? If so, anyone have any experience with the direct replacement units Harbach sells?
     
  2. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Those little shaded pole motors are very easy to dismantle and clean. If the problem was mine (and it has been in the past) I'd try that before getting a new one.

    [​IMG]

    Use "air tool" oil to clean up the bearings and felts. Motor oil plugs up pores in the sintered bronze bearing.

    Fix it soon or the rotor shaft will be damaged and you'll need a new motor for sure.

    PS: I haven't had to replace one of these motors yet. They almost always clean right up in less time than it takes to open and close the box.
     
    Last edited: May 20, 2020
    W2VW, W1TRY and K1LKP like this.
  3. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

    HI JAMES,

    GREETINGS FROM SALEM, NH.

    KD2ACO HAS PROVIDED YOU WITH SUPER
    INFO ON HOW TO REPAIR THE FAN...BRAVO..

    TO ANSWER YOU QUESTION???

    should I take this as a sign that it's time to replace the entire motor assembly?

    YES...........YES.... YOU MUST TAKE THE TIME TO REPLACE / REPAIR THE ENTIRE FAN ASSEMBLY.

    IF THE FAN FAILS, THERE IS A GOOD CHANCE YOU WILL HAVE A
    MELT DOWN IF YOU DON'T NOTICE THE FAN FAILURE IMMEDIATELY.


    THREE CHEERS FOR 4U1UN........BRAVO........

    JAMES, PLEASE GIVE MY REGARDS TO THAT OLE CW RASCAL VE3QAM - MARK.

    WE HAVE BEEN GUD CW FRIENDS FOR MANY MANY MANY YEARS.

    73 - K1LKP


     
    W2VW likes this.
  4. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    We can agree to disagree, Carmen. :p

    I've never seen a shaded pole motor just quit due to an open coil, which is about the only thing that can happen to it if the bearings are cleaned once a year.
     
  5. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

    CHRIS..........BRAVO........GREAT JOB ON THE PHOTO AND INSTRUCTIONS.

    YOUR NOTES ARE WHAT I CALL "ABSOLUTE SESAME STREET INSTRUCTIONS "........

    KEEP UP THE GREAT WORK FOR THE HAM COMMUNITY.

    73 - K1LKP
     
  6. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

    HI CHRIS,

    WHAT HAPPENED TO ME MANY MANY MANY YEARS AGO ON MY SB 220

    IS THAT THE FAN BLADE ACTUALLY WORKED ITS WAY BACK TOWARDS

    THE BODY OF THE FAN MOTOR AND JUST LOCKED UP THE ROTOR.

    THE FAN BLADE WAS NOT RESTRAINED TO THE MOTOR SHAFT WITH
    A LOCKING SCREW - IT WAS SORT OF A PRESSURE FIT RING AROUND
    THE COLLAR OF THE BLADE.

    ANYHOW, THANKFULLY MY WIFE HAD WALKED INTO THE SHACK
    AND SAID TO ME WHAT IS THAT FUNNY SMELL IN THE SHACK.

    WELL IMMEDIATELY I JUMPED UP AND LOOKED INTO THE
    AMP AND CUD SEE THAT THE BLADE WAS FROZEN.

    PRAISE THE LORD THE REPAIR WENT WELL AND AFTER THAT
    I BUILT UP A LARGE EXHAUST ASSEMBLY THAT FIT ON TOP
    OF THE SB 220 THAT KEPT THE INSIDE COOL AS A CUKE.

    KEEP SMILING AND SAFE WITH THIS DARNED CORONA VIRUS SITUATION.

    73 - K1LKP
     
    KD2ACO likes this.
  7. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Thanks, Carmen, but I'm a small player here... but can see your valid points as well. That's a scary prospect!
    ~~~~~~~~~~~~~~~~~~~~~

    If the motor comes apart and the rotor shaft is scored or the fan doesn't fit tightly, then I'd get a new motor. 50 bucks is a bit steep, but your time is worth something to keep from searching for a similar motor, etc.

    In all regards, it a very good idea to take the amp apart every once in a while to clean it out with compressed air and inspect it carefully to head trouble off at the pass! The new or rebuilt motor should have 2 or 3 drops of tool oil applied to the felts every year or so.
     
    Last edited: May 20, 2020
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

    I use Singer Sewing Machine oil for lubrication.

    Works good and last a long time.
     
    KD2ACO and K1LKP like this.
  9. K1LKP

    K1LKP Platinum Subscriber Platinum Subscriber QRZ Page

    HI CHRIS,

    I HAD BUILT UP MY SB 220 BACK IN JAN. OF 1972 AND IT WAS A REAL WORK HORSE.

    THIS IS A PIX OF THE ADDITIONAL FAN ASSEMBLY I BUILT UP TO PUT ON TO OF THE SB 220.

    IT ACTUALLY CONTAINED TWO (2) MUFFIN FANS TO EXHAUST THE HOT AIR FROM THE
    CABINET.

    K1LKP_1978 SB 220 AMP.jpg
    AS YOU CAN SEE IN THE PIX, I ALSO KEPT A DIAL TYPE TEMPERATURE DEVICE TO MONITOR THE HEAT.

    THE SB 220 AND THE TR - 4 HAVE GONE TO HAM RADIO HEAVEN.

    I STILL HAVE THE JAMES MILLEN XMATCH THAT I PURCHASED DIRECTLY AT THE
    FACTORY BACK IN 1964.

    I AM 76 NOW AND STILL HAVING FUN WITH THIS WONDERFUL HOBBY.

    73 - K1LKP
     
  10. K2QI

    K2QI Ham Member QRZ Page

    Thanks to all (especially Chris) for the great info. Looks like I'll be tearing the motor apart later today.

    73!
     
    KA9JLM likes this.

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