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811A tubes holding up

Discussion in 'Amateur Radio Amplifiers' started by N5WVR, May 19, 2017.

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  1. N5WVR

    N5WVR Ham Member QRZ Page

    With so many people expressing concerns about 811A tubes, melted plates, poor dissipation, etc., etc. I decided it would be a good idea to open up the AL-811H that I bought last summer and see how they looked after a year of casual use.

    I typically tune up at 600 watts CW using W8JI's recommended method, then reduce power and aim for 500-600 watts PEP on the meter. I don't see any benefit to pushing for 800 watts. My amplifier operation is 95% SSB, since I usually do CW operation at 50 - 100 watts.

    I have begun dipping my toe into the contest pool, scoring high enough in several state QSO parties to get a certificate. In our home Vermont QSO party, I worked over 500 contacts, nearly all done using this amp at 500+ watts over a period of many hours, and frequently calling CQ.

    When I opened the amp, the tubes looked as though they had come from the factory. I could not see any trace of melting, no welts, no black deposits, no indication of any damage. I didn't remove them from their sockets, so I couldn't see every part of the tube, but I would have expected some indications if they had suffered from use.

    The amp still puts out 600 W at tuneup, and 500-600 watts SSB PEP with about 40 - 50 watts drive depending on the band.

    IMHO, concerns about these tubes are overblown. They can perform very well and will be very cheap to replace when they fail.
    N2EY, KQ9J and WA7PRC like this.
  2. N7WR

    N7WR Subscriber QRZ Page

    I agree with you. Proper tune up and not over-driving to get the last possible watt out of them will lead to long tube life. 600 watts out of the AL 811 H is reasonable. Pushing it up towards its advertised 800 watts is not
    N2EY likes this.
  3. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    There were some bad runs of 811As from China that were pretty poor but it seems "today" they're better. Whoever's making them "fixed" whatever their problem was.

    But even with very good 811As, the tune-up procedure is important. Some newbies who have never tuned up anything with tubes in it "key down" for way longer periods than the tubes can handle, and the tubes fail because of that.

    Older ops who are very familiar with tuning up tube type rigs don't seem to have this problem at all, and 811As can last decades if treated properly.
    N5WVR and WA7PRC like this.
  4. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    What brand are the 811's? Did you buy the amp new or used?
    I've purchased new Taylor 572's and some 6146's around new year's and they are holding up very well after some heavy use... just took a peek and they also look new still. Things are looking up in the new tube dept. at least for these. I think Steve WB2WIK mentioned that the new 3-500's are also doing well now. A couple years back, there was despair in the air. This is a big relief! :)
  5. N5WVR

    N5WVR Ham Member QRZ Page

    I bought the amp brand new late last summer, so the tubes would be whatever Ameritron is currently shipping in its new amps. I assume they are representative of what's coming off the Chinese assembly line these days.

    KD2ACO likes this.
  6. N5WVR

    N5WVR Ham Member QRZ Page

    W8JI recommends no more than 5 seconds of tune-up followed by 15 seconds of standby to let the tubes cool. I can usually do it in no more than 2 -3 seconds. Of course you have to do it three times, once to get the plate tuned at 20 watts, once to get the load tuned at 65 watts, and once to get the plate fine-tuned at 65 watts. Each time is about 2 - 3 seconds with 10 - 15 seconds of standby in between.

    I use key-down tuning, not high-speed dits.

    N2EY likes this.
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    You are doing good.

    Your amp should last a long time.

    N2EY likes this.
  8. KC9VFO

    KC9VFO XML Subscriber QRZ Page

    My two yr old 811 H tubes are holding up fine also. I run the amp almost daily ( a littlle less often these days ) between 700 and 800 watts SSB . Some folks (especially on another forum) sound like a broken record ,repeatedly bashing these amps. Nothing wrong with mine and I run it hard.
    W2AI and KR2C like this.
  9. W2AI

    W2AI Ham Member QRZ Page

    About 30 years ago, a company named AMP Supply Company manufactured linear amplifiers for amateur service. One of the amplifiers , LA-1000A, used four TV sweep tubes (6MJ6s) at the time. The company advertised that TV sweep tubes were cheap and plentiful. Needless to say; TV sweep and CR tubes went the way of the dinosaur in the 1990s and tube manufacturers no longer made them making the unit obsolete. The 811 tubes are primarily RF transmit tubes that have always been utilized in amateur radio in either commerial or homebrew amps. The AMP Supply Company went out of business in the 1990s. I own an Ameritron AL-811H amp for the past 7 years and must say its worth the money in terms of RF power delivery.
  10. W2AI

    W2AI Ham Member QRZ Page

    Grid current on the AL-811A can NOT exceed 200 ma or the tubes will be destroyed in short order. MFJ has an add-on modification circuit board that will automatically shut down the amplifier if the grid current exceeds 200 ma during key down tune-up.

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