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Linear repair

Discussion in 'General CB Services Discussion' started by 357magnum, Jul 26, 2017.

  1. 357magnum

    357magnum Well-Known Member

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    Hi all , I had a problem with my Gray transistor 2 pill amp the other day I got it working but it hasn't been touched in over 25 years . I'm looking for suggestions for a Good place to send it . I tried getting in touch with Gate Keeper but he doesn't get back to me , he must be too busy or side tracked . Thanks for any help , Leo


     

  2. rabbiporkchop

    rabbiporkchop Well-Known Member

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    LoL. Gatekeeper is probably the last redneck I would let tweak on an amplifier.
    I'm sure there's plenty of folks in this forum that will point you in the right direction.
     
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  3. nomadradio

    nomadradio Analog Retentive

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    Good question. Seems like anyone with a decent reputation has a six-month backlog.

    And anyone who can do the job quickly has a bad reputation.

    Part of the problem is pure economics.

    Let's consider the worst case. Amplifier has two bad RF transistors that will cost the customer 90 bucks for the pair (could be more). The 35 year-old relay is also bad. Add another 30 for that. The labor to get it fixed up would be another fifty, at least. Now, if the customer carried it in through the door, he could get it fixed for 170 bucks when he comes back to pay for it and take it home. Probably won't want to, since a working used amplifier will probably be cheaper.

    But this is the worst case. This amplifier got shipped into the tech. He'll spend 15 bucks' worth of labor to unpack it and write up the customer's address info. Another 30 bucks labor to find out all that's wrong with it (and write it up). Packing it back up to send home takes longer, maybe 20 bucks labor. The shipping cost to send it home (with insurance) is another 20 bucks.

    So, the price just to give the customer the bad news itemized in dollars and cents is 85 bucks, more or less. Add to this the shipping cost getting it to the tech in the first place, and we're past that magic hundred-dollar threshold.

    Just for bad news.

    This scenario is one of the (many) reasons we don't solicit people to "just send us" this kind of repair job.

    No easy solution to this dilemma.

    73
     
  4. 357magnum

    357magnum Well-Known Member

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    Thanks Nomad , I understand the economics , I just put it out there amp works fairly well but has an RF issue when on Max . I just thought it might be better to just get this one a once over also my late father got me this years back so it has a little meaning to me but then again I suppose I could just set it in the shack and buy a new one .LOL 73 and God Bless , Leo
     
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  5. Loyal Servant

    Loyal Servant Well-Known Member

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    What about the scorpion repair shop?
    Anyone dealt with him?
     
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  6. Big Kahuna

    Big Kahuna Well-Known Member

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    I'm all for keeping old equipment running, but not worth it for that amp. if the issue is only at max then just don't run it at max. If you can't live with the problem than just buying a new 2 pill is probably the way to go.

    I had lots of grays over the years and I liked them but I also never paid more than $100 for one so I wouldn't put more than $20 into repairing one.
     
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  7. 357magnum

    357magnum Well-Known Member

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    Yes Big "K" exactly what I have been doing .
     
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  8. StrangeBrew

    StrangeBrew Sr. Member

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    What exactly is it doing? If it only acts up on max you could be driving it to hard.
     
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  9. nomadradio

    nomadradio Analog Retentive

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    Old amplifiers were built for wimpy radios. Over the years the radios have gotten larger, decade by decade.

    Old amplifiers remain the same size. Good chance you don't have a radio small enough to match this amplifier's "Max" mode.

    73
     
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  10. 357magnum

    357magnum Well-Known Member

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    I learned not to over drive many years ago only 1/2 watt in and always keep my modulation in check . Thank You 73 , Leo
     
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  11. 357magnum

    357magnum Well-Known Member

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    Thanks Nomad but I think it's just got old age like I posted to SB , I usually run about a 1/2 watt in but on back of amp it's states " 4 watts max " I tried different settings on radio for wattage but it didn't change . I won't use Max til I figure it out . 73 and God Bless , Leo
     
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  12. 357magnum

    357magnum Well-Known Member

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    I should have stated it when I started the thread but forgot , I run a Cobra 2000 with adjustable wattage from 1/2 watt to about 10 with a D 104 Silver Eagle or I use my Tuner SSK .
     
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  13. nomadradio

    nomadradio Analog Retentive

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    The radio should not be too large for it. We have had some luck stabilizing old Gray amplifiers by adding negative feedback to each RF transistor. A 0.1uf disc cap in series with a 100 ohm 2 Watt resistor goes from collector to base on each RF transistor.

    Fair warning, this tends to reduce the amplifier's input impedance. Tweaking the matching capacitor on the input transformer's primary may prove necessary to get the input-side SWR back down to an acceptable level.

    Some of the late-1970s two-transistor amplifiers used TRW and SSC brand stud-mount transistors that would overdrive with 8-Watt modulation peaks. Turning down the carrier would not fix that. Adding resistors between the relay and the input transformer's primary was the only way to keep the modulation peaks from flattopping.

    Oh, and if your Gray amp has the "Billy" neutralizing link in it, you should be able to unwind it after NFB is installed on the transistors. This unique "feature" has the wire to the antenna socket's center pin and the wire to the radio socket's center pin twisted together as a pair between the rear panel and the circuit board. This trick was an attempt to neutralize the amplifier and prevent it from oscillating.

    Doesn't work. I have always blamed this technique on Billy D. Ward. Never tried to pin him down about who had this cornball idea.

    It doesn't do what it's intended to do.

    73
     
  14. 357magnum

    357magnum Well-Known Member

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    Wow Nomad ! You know your stuff just sorry we never chatted before so I can follow you ! I'll take care of that as soon as I'm done here . It must be old age because it never did this before . But I thank you for your input my new friend !lol
     
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  15. Turbo T

    Turbo T Certified CB Rambo

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    Funny you mention that. I've been watching some of his videos. You know how listening to someone talk it can give you negative vibes? That's what I get from him.
     
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