Icom ic 2100 2mtr tx hum

Discussion in 'Radio Circuits, Repair & Performance' started by M6OQU, Aug 3, 2018.

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  1. M6OQU

    M6OQU Ham Member QRZ Page

    hi all i have a older model 2mtr Icom , ic 2100 , and its just started to hum badly on transmit , rx is fine .Does anybody have any knowledge of this problem and how to go about fixing it ? thanks Nigel
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    What is your power supply ? Battery ?

    It should hum a little if PL is on.
  3. M6OQU

    M6OQU Ham Member QRZ Page

    hi there power suply is a new 30amp one and hum is over the voice by loads , think its internal ?
  4. K8ERV

    K8ERV Ham Member QRZ Page

    Can you check the PS output with a scope, or try a battery supply?

    TOM K8ERV Montrose Colo
  5. G4COE

    G4COE Ham Member QRZ Page

    Try a different mic. even if it means borrowing one.

    Try a different power supply or try another rig on the power supply.

    Make sure the mic. is not too near the power supply? A magnetic mic. will pick the magnetic field up from the mains transformer, this 'hum' will vary as you move the mic.

    Loose grounding screws in the rig holding the circuit boards down, while cover is removed look out for bulging electrolytic capacitors.... they may well have a domed top rather than being flat.

  6. M6OQU

    M6OQU Ham Member QRZ Page

    hi all thanks for the info , i have put another radio on the power supply and it works fine and it was on the same antenna , clamped 2 ferites onto the mains cable ,so testing that ,then will try a new mike and lastly ill test the caps ...watch this space !!
  7. G4COE

    G4COE Ham Member QRZ Page

    One question I forgot to ask, does it hum on receive or only on TX ?????

    If it hums only on TX then it's probably RF getting into the mic. or power supply, one cure may be ferrite core on the power supply leads, DC as well as mains power cord, try one on the mic.

    Try using a balun to stop RF coming down the braiding of the feeder, even shifting the power supply *might* help here, be sure to keep the aerial feeder away from the power unit and the mic lead.

    I had RF feedback on a Kenwood MC60, I earthed the base plate and added a link, from mic. ground to screen ground on mic. socket on it's base unit.... thought I'd just mention.

  8. K8AI

    K8AI Ham Member QRZ Page

    The receiver you're detecting the TX hum on... Could it be not filtering out the PL tone? Try transmitting with the CTCSS tone off. Just a thought.

    Oops, I didn't see your last reply. Disregard.
  9. M6OQU

    M6OQU Ham Member QRZ Page

    update..all cured as was advised to clamp clipon ferrites to power lead and mike and hey presto no hum ...thanks all for your help
  10. AI4RA

    AI4RA XML Subscriber QRZ Page

    Thanks for the info, M6OQU! Threads like this are very helpful to those of us who have older rigs and all of a sudden run into problems with them. I also have an older IC-2100 series model (mine is an IC-2100H) but use it mobile, so have not experienced the issue you have with an AC-based power supply (assuming yours uses 240 V, being in England, correct?). Interesting that you also put ferrites on the mike as well as the power cable - does it work OK if you have the ferrites only on the power cable??
    KB0MNM likes this.

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