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Yaesu FRG-7 vintage budget comms. receiver

Discussion in 'Radio and Wireless' started by radar.bob, Jul 17, 2018.

  1. radar.bob

    radar.bob

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    Feb 18, 2018
    Just wondered if anyone is familiar with these old radios. The red "lock" led should normally be on, until the wadley loop system
    is tuned in, locked, and then the led should go out. It kind of works the opposite way you would think it would.

    My problem is that now, the led is permanently out, the unit is totally out of whack, and receives nothing.
    This only happened since we got into the warm weather, so suspect the fault is temp related. To confirm this
    I'll cool the set down in a spare refrigerator and see what happens.

    Just curious if anyone has come across the above problem before, and could point me in the right direction.
    Have a schematic diagram.

    Thanks for reading.
     
  2. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Even if it works coming out of the fridge, somebody will have to open it up and look for the problem.
    If you have basic troubleshooting skills, open it up and look for any physical (burned parts) obvious problems.
    If it works coming out of the fridge, get a can of 'freeze spray' from a local electronics parts repair store, and use
    the cooling mist sprayed on each semiconductor, until you find the problem.
    My guess however, is that it won't work any better once out of the fridge.
    If you've got troubleshooting skills, open it up and look around inside. If not, you'll have to find somebody who repairs your unit.
     
    davenn likes this.
  3. kellys_eye

    kellys_eye

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    Jun 25, 2010
    What test equipment do you have?
     
  4. radar.bob

    radar.bob

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    Feb 18, 2018
    Guys- sorry if I seem to be replying to myself, or starting a new thread. Still getting used to the site.
    Anyway- thanks for the answer(s) re my sick FRG-7.

    Cooling down made no difference- guess it was a coincidental thing. The radio is just getting old!
    Covers have been off a long time due intermittent nature of the fault.

    I shall have to start scoping through it, and pay particular attention to the RF/OSCR/HARM.GEN. pcb's.
    Obviously checks for swollen electrolytics, and any signs of overheating, were checked prior to posting.

    The only test gear available is a Fluke 87 multimeter, a Capacitor Wizard ESR meter, a Peak Atlas
    Component Analyser, a 0-30Vdc psu. and an old Phillips 50Mhz dual beam oscilloscope.

    Feel sure I can repair this on my own- just hoped for a quick fix- eg ck TR. abc on PCB. xyz = common failure.

    Thanks for your time.

    Bob.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    24,860
    2,571
    Jan 21, 2010
    It might be useful to start looking at either the ESR of filter capacitors and/or ripple on the power rails (any the rail voltages)

    This is pretty simple, and while there's nothing specifically pointing to this as a problem, it will give you confidence in the power supply.
     
    kellys_eye likes this.
  6. kellys_eye

    kellys_eye

    4,289
    1,143
    Jun 25, 2010
    VFO stability is key to the receivers operation and as Steve suggests this could be down to a simple issue with supply regulation.

    A frequency counter would be useful to test the various oscillator outputs (given that there's a quite a few of them!) and it's not easy to do with just a scope.

    Fortunately, DFM's are quite cheap these days - even the cheap Chinese knock-off's have decent accuracy too (if you go by the Youtube reviews I've seen). Worth investing in one. AND, whilst you're at it (ordering from China that is) get one of their multi-component testers (LRC/semi) as they are VERY good units for all sorts of components.
     
  7. radar.bob

    radar.bob

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    Feb 18, 2018
    Will check all dc rails with scope, to check if ripple present. Will then check o/p's from oscillators and harmonic generator.

    A DFM set to fast sampling rate would be very useful - as suggested - will order one asap. Will check on the LCR unit as well. For some reason never considered test gear from China b4. Thanks for the advice.
    Need to think about an rf sig. genr. as well
     
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