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Thread: 10 Meter Amp

  1. #1
    "Island Bartender" KG4CGC's Avatar
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    10 Meter Amp

    I recently acquired a 250 watt 10 meter amp that works well with 100 watt rigs when power into the amp is set to 10 watts.
    The output is fine. It runs cool to the touch even when I get long winded into a nice wire antenna cut to the middle of the 10 meter SSB voice band allocation. I get peak power up to 320 watts. The problem I encounter is when I turn the amp on. It immediately attenuates the receive signal by 20db.
    What should I look for first?
    This is a generic, brick type amp made before the surface mount RM Italy stuff came out. Sadly, it did come from an 11 meter environment. Estate sale stuff.
    Of note, I replaced a burnt fuse as soon as I bought. It was inexpensive. Sold as not working.
    Thanks ahead of time.

  2. #2
    Administrator N8YX's Avatar
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    Look at the T/R relay. And...is it a so-called "bilateral" unit? In other words, is there a receive preamp built in?

    Dirty relay contacts in either the T/R changeover or the preamp in-out circuits will cause what you're seeing. Another possibility is the carrier-operated relay turning itself on at power-up with no drive applied. For that I'd see about getting a schematic then looking at any time-delay capacitors on the detector side of that circuit.
    "Everyone wants to be an AM Gangsta until it's time to start doing AM Gangsta shit."

  3. #3
    "Island Bartender" KG4CGC's Avatar
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    Ah, yes. There is a pre amp switch. It does nothing in the on position.

  4. #4
    Administrator N8YX's Avatar
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    Quote Originally Posted by KG4CGC View Post
    Ah, yes. There is a pre amp switch. It does nothing in the on position.
    I'd suspect its changeover relay (if so equipped).

    What's the model of the amp?
    "Everyone wants to be an AM Gangsta until it's time to start doing AM Gangsta shit."

  5. #5
    "Island Bartender" KG4CGC's Avatar
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    Palomar 250HD Class AB.

  6. #6
    Administrator N8YX's Avatar
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    "Everyone wants to be an AM Gangsta until it's time to start doing AM Gangsta shit."

  7. #7
    "Island Bartender" KG4CGC's Avatar
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    No. It more resembles a Texas Star.
    I will add some pics later this evening or tomorrow evening.
    Thank you for your interest.

  8. #8
    Whacker Knot WTKX's Avatar
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    Whew.

    I don't wanna take the rap if it was "Dave Made".

    Suspect the pre-amp stuff. Maybe you can by pass it.
    Most of the time we are punished if we go against the trend. Only at an inflection point are we rewarded. ~ George Soros



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  10. #10
    Administrator N8YX's Avatar
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    I think yours is a predecessor to the amp in the link I posted (the hi/med/lo power switch controls bias and input attenuation). Open yours up, Charles, and compare the actual PCB with the schematic in the link. Similarities?
    "Everyone wants to be an AM Gangsta until it's time to start doing AM Gangsta shit."

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