IC-7300 main CPU failed

Discussion in 'Radio Circuits, Repair & Performance' started by BH7JUO, Oct 19, 2017.

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  1. BH7JUO

    BH7JUO Ham Member QRZ Page

    hello all
    I found a IC-7300 which can't power on, it's short on 3.3V power line, seller said he detected that main CPU chips was failed. Who know whether this CPU chip contain some firmware, or it just a processor that firmware all storing in outside EEPROM?
    main processor is R7S721000VCFP
    EEPROM is EN25O64

  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    The CPU appears to be a ARM processor with no on-board ROM.

    How was it determined that the 3.3V short is internal to the CPU ?

    Good Luck.
  3. SM0XHJ

    SM0XHJ Ham Member QRZ Page

    A short inside the CPU seems a bit unlikely. If the short has indeed been located to/near the CPU, check the leads and pads for tin whiskers. If the board hasn't been coated properly, that is a more likely place for a short.
    Last edited: Oct 19, 2017
  4. BH7JUO

    BH7JUO Ham Member QRZ Page

    Thanks KA9JLM and SM0XHJ.
    This IC-7300 not in my hand, seller told that it had been applied high voltages (maybe 24, 36 or 48V DC) into DC port.
    I have no ask how he determine short location in CPU chips, if apply high voltages, I consider that if other 3.3V chips also hurting or broken.
    EEPROM is EN25Q64.
    Buy this radio is a bet...
    Last edited: Oct 20, 2017
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    You may get lucky and only the 5v and 3.3v regulators shorted.

    Good Luck.
    K8AI and W1BR like this.
  6. K6BRN

    K6BRN XML Subscriber QRZ Page

    If you'd like a working radio for a reasonable price, WALK AWAY from this "deal". If the FPGA board has been damaged it will cost you 2/3 of a new radio to repair it. 48 VDC is more than enough to defeat input power protection and toast MANY items on several boards: Memory, CPUs, ADCs, DACs, FPGAs, oscillators. Not to mention latent damage that crops up later or degrades performance. The list is endless.

    But if its a free radio you can throw into the parts bin, go for it.

    Brian - K6BRN
    YO3GFH, KF5RRF and KA9JLM like this.
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    I agree. It can be like a lightning strike.

    Many times it will blow holes in ICs, If you shake the radio you can hear IC chunks rattling. :eek:
    W1BR and KF5RRF like this.
  8. BH7JUO

    BH7JUO Ham Member QRZ Page

    Many thanks Brian and Don,
    That's what I consider----He priced it about half of new one. In case of not only CPU failed, it will take too much money and time to repair other components as Brian said...
    This bet isn't worthy. I just gave up.
    Last edited: Oct 23, 2017
    KA9JLM likes this.
  9. WA9SVD

    WA9SVD Ham Member QRZ Page

    If over voltage (much more than 16 Volts DC) such as 24, 36, or 48 volts, many, if not most semiconductors are probably toast. IF that is true, it's not just the CPU, and the radio is probably only good for a doorstop. It might have been able to briefly survive application of 20 Volts, but above that, I'd give it little chance of survival.
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    How does one accidentally connect 24 volts to their radio ?

    That must have taken some talent.
    W1BR and WR2E like this.

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