IC-7300 plus linear amp warning

Discussion in 'Software Defined Radio (SDR)' started by G0GSR, May 21, 2019.

ad: L-HROutlet
ad: l-rl
ad: L-MFJ
ad: Left-3
ad: abrind-2
ad: Left-2
ad: Subscribe
  1. G0GSR

    G0GSR Ham Member QRZ Page

    Latest traces below, showing the effect of the 100uF mod. with the current firmware.

    Normal, untouched condition showing the amp hot switching fault.

    Now with the 100uF capacitor mod. showing a 2mS delay before the amp is un-keyed.

    I just used the supplied 13 pin DIN to flying leads with the 100uF soldered between Red (-ve) and Orange (+ve).


    Last edited: Oct 8, 2020
    W1TRY and KD2ACO like this.
  2. KE3HJ

    KE3HJ Ham Member QRZ Page

    Thank you, Frank! A simple, low-cost solution to a long-lasting problem for many users, notwithstanding the 'Tune Switch' behavior. Should only be a problem, and not a big one, if an external tuner after the amp is connected via the ICOM tuner interface, as I understand it, since one would likely not be using the internal tuner when connected to an amp. Correct?
  3. G0GSR

    G0GSR Ham Member QRZ Page

    True but in my case, I use a "tune switch" connected to the external ATU socket to generate 10W to adjust my manual ATU.
    So after testing the capacitor mod, I built the proper delay circuit.

    Bottom line: Icom need to fix this fault.

  4. KE3HJ

    KE3HJ Ham Member QRZ Page

    Agree. So simple for them to fix it. Thanks, Frank.
  5. W2BLC

    W2BLC Ham Member QRZ Page

    Now I have to ask: Has anyone experienced identifiable and proven damage to their amplifier because this problem?
    Has anyone experienced material ($$$) loss or repair expense due to this problem? If you answered yes to either or both questions - did you attempt to collect damages (cost of repairs etc.) from Icom? Did you get reimbursed for your loss from Icom?

    Just thought I'd open the can of worms from a different direction.
    W1TRY likes this.
  6. G0GSR

    G0GSR Ham Member QRZ Page

    Icom must be worried.
    Their lawyers are now posting here :)

    K3RW likes this.
  7. W2BLC

    W2BLC Ham Member QRZ Page

    I asked the question to ascertain if anyone had experienced any direct dealings with Icom regarding this design issue? Has anyone been told to take a "hike" over this issue by the manufacturer? There are remedies available. Or, is this series of postings more theory than practice?
  8. G0GSR

    G0GSR Ham Member QRZ Page

    Personally, I have raised TWO support requests to Icom (UK)
    I have had nothing but an automated reply to each.

    But for me, as an engineer, having proved that this fault exists and how serious it is, is enough for me to take action to prevent relay damage.
    Imagine switching a 1500W carrier with a relay contact. There is no doubt in my mind that damage IS being done.
    Whether the operator has noticed yet is another matter.
    Contact burning and erosion IS taking place and WILL eventually lead to a premature failure.

    Switching an RF relay on power is a very bad thing to do.

    KD2ACO likes this.
  9. K8DO

    K8DO Ham Member QRZ Page

    You / we have to understand Japanese society. Face (your street rep) is your life in their corporate business world.
    To us this is a simple technical glitch and needs a fix - "so, fix it!" the boss thunders and stomps back to his sumptuous corner office, glaring and chomping on his cigar.
    They have group meetings where everyone in the corporate chain, from the first pencil sketches, to engineering, manufacturing, and sales examines every tiny nut and screw on the product and signs off on it long before it is sent out to the public for purchase. (one of the reasons for their ascendancy as a manufacturing power)
    In their society admitting there is a glitch is admitting they were ALL wrong. They will die before they do that
    (think Okinawa, Peleliu, Corregidor, and their soldiers found still hiding in the jungle 50 years later because the emperor said, to the death)
    So, sending complaints to low level corporate office slaves will get you a form letter in reply - period.
    No way in hell that clerk is going to make waves and have to stand (trembling) in front of THE boss.. (one of the reasons for their failings as a manufacturing power)
    So, we fix it on our own and move on - with an otherwise excellent radio for the money.
    N9LCD likes this.
  10. N9LCD

    N9LCD Ham Member QRZ Page


    If you want a good view of the Japanese "mentality" read "Midway,The Battle That Doomed Japan" by Mitsuo Fuchida and Masatake Okumiya.

    Fuchida is best known for leading the attack on Pearl Harbor. Okumiya rose o the rank of Major General in the post war Japanese air force. These guys were there at Midway and really lay it on the line.

    PS: This is not an "easy to find" book. My copy is from the 2001 printing.

Share This Page