Alpha 87a Amp question

Discussion in 'Amateur Radio Amplifiers' started by K0MB, Aug 10, 2019.

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  1. K0MB

    K0MB XML Subscriber QRZ Page

    I am considering a used 87a amp at what is an agreeable price to me. Are there any inherent problems that have manifested after 30 some-odd years that should serve as cautions, or warn me off of this purchase? My antenna is a non-resonant 132' dipole fed via window wire via a capable Heath roller tuner.
     
  2. AD6W

    AD6W Ham Member QRZ Page

    Had to replace a noisy blower in mine after 15 years, not an easy job. Other than that I just blow dust out of it once in awhile. Mine bought new in 1996 from factory guys in the Alpha booth at the Visalia DX Convention. Used several times a week, now mostly low bands. Helped me confirm 2500 band countries in the DXCC Challenge from a small city lot with a modest 7-band trap beam and shunt-fed tower 80/160. Sometimes I leave it on up to 48 hours if there is a DXpedition cooking on several bands I need. Original tubes, still full output with 45 watts drive, have it in a separate room where it sits quietly and does its job. Protection circuits have preserved the tubes from every dumb thing I have ever done to it. Still has the original ROM. I do keep it terminated into a dummy load when not in use, protects the PIN diodes from any transients. If the original owner had no problems, I doubt you will, but it is a complex device a couple decades old. The way its going mine will probably outlast me.
     
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I think you've been lucky.

    Alpha always made very solid amps, including the 87A, but the 87A and some other models are almost like a "computer with an RF amplifier dongle attached" and have a lot of control circuitry -- which in my experience is what fails, not the RF part. Sometimes just a loose or oxidized connection at one of the many internal connectors, which is a zero-cost repair if you find it.

    From an "RF" perspective, they're spectacular.

    I actually prefer the even older Alpha amps that don't have all the computer stuff, like the old 77DX, 77SX, 374, 374A, 76 series, 78 series, etc. The only issue with the ones using 8874s, 8877s and 3CX800A7s is the cost of replacement tubes!
     
  4. AD6W

    AD6W Ham Member QRZ Page

    I assume anyone looking at the 87A or any other automatic band switching amplifier must have a need for remote operation or fast band switching or they would be looking at a manual control amplifier. I need remote capability; I guess you don't. Apples and oranges. When I was contesting I needed automatic band switching, just like many other contesters, and some blind operators who also find it necessary. I got my money's worth when the 87A made the 10 year mark without a failure. 13 more years of reliable operation after the first 10 have been an unexpected bonus. How long are these things supposed to last? When I was engineering products for the industrial computing market our design life was 10 years, so that tends to set my expectations. If your point is the complexity of the 87A assures that it will have less statistical reliability over time than a manually-tuned amplifier, I totally agree, but that's a trade-off acceptable to me for the functionality needed.
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    No real argument from me.

    I had an 87A but never used it for remote operation and its protection features kinda drove me nuts. That was >20 years ago and since I don't do "remote" and can easily keep an eye on parameters, I use manually tuned amps now -- but also ones where grid current isn't destructive so even mistuning doesn't matter much (except for IMD).

    I actually sold the 87A in favor of a Henry 3K Premier which used a 3CX1200D7 that has 50W grid dissipation so it was almost impossible to overdrive or exceed its Ig rating -- I'd tune it, but not a lot. It's also "instant on," so no 2-3 min warmup time. Nearly indestructible, but no way to remote that!:p
     
  6. W1QJ

    W1QJ Ham Member QRZ Page

    They are fantastic amps when the work.
     
  7. K0MB

    K0MB XML Subscriber QRZ Page

    Henry amp are rare beasts here in the east.
     

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