ICOM IC-7300 Over-voltage Repair

Discussion in 'Radio Circuits, Repair & Performance' started by KC3FKR, Jul 19, 2018.

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  1. WA9D

    WA9D Ham Member QRZ Page

    I was just "reading the mail" of the newsgroup version of this thread, and am dropping in with a possibly relevant comment...
    I haven't been inside a 7300, but this sounds to me like it is a diode intended to protect against polarity reversal. That would be a typical place to put it, where power comes into the circuit, with the diode installed so that it draws lots of current if power is applied backwards, hopefully blowing a fuse in the supply. But it would also have a maximum reverse voltage, and if your over-voltage exceeded that I think it would fit all the symptoms I read here. It would just be a diode with little forward resistance and fast turn-on.
    I wondered why that would be put at the input just to that part of the radio, not to the main power input, but maybe they did this separately for each major subsystem.
    But anyway, good luck with it.
    Bob W, WA9D
    WB9YPA likes this.
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    I think ICOM was smart using a fuse where it is needed.

    Many operators do not fuse the power cord properly, And the fuses inside of the radio can protect it.

    Finding the fuse can be tricky, Because of the microfuse they may have.

    Without a fuse the reverse polarity diode is useless, Except for the firecracker sound it makes when it blows apart.

    A fuse is your friend.
    WB9YPA likes this.
  3. KP4AJ

    KP4AJ XML Subscriber QRZ Page

    Hi All:

    Thank you very much. This post may have changed my mind in favor of IC-7300 vs Kenwood 590SG re next rig upgrade. Right now using 480SAT. 590SG USB port problem verified through other post in Internet.

    Later and 73'

    WB9YPA likes this.
  4. WB9YPA

    WB9YPA Ham Member QRZ Page

    What's even better is that ICOM used a standard blade type 5A fuse available at any automotive store and it is very easy to find on the board.
  5. AA1FR

    AA1FR Ham Member QRZ Page

    Thanks for this info.

    It is great they are not following planned appleesence. Try to fix your multi-thousand dollar apple workstation. no parts or schematics available.

    I will discuss with Icom the right to "repair" movement going on, see if they are into it.

    If i discussed this in an Apple support forum, it would get deleted.

    Although i am retired and inert shop, I would help anyone on air with fixing stuff.

    willing to tear apart my 7300 for test points to share with others.

    btw, my state of Maine gives a 4 year warranty to consumer products.

    Read the fine print in your warranty.

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