Advice with an 811H amp

Discussion in 'Amateur Radio Amplifiers' started by K1OIK, Dec 29, 2017.

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  1. K1OIK

    K1OIK Platinum Subscriber Platinum Subscriber QRZ Page

    The glass is not cracked.
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Sounds right, but the seller might be if he claims they're "real" 811As without testing them at 1.7kV at 30 MHz.

    As previously stated, I see lots of "811A's" sold for audio amplifier use and many of those won't function at 1.8kV and HF radio frequencies. It's possible this is what you got.
  3. K1OIK

    K1OIK Platinum Subscriber Platinum Subscriber QRZ Page

    The seller said:
    The tubes were 811A's. They were pulled from my Ameritron AL-811 Amplifier. 5 years old. Offered up for sale as I received three fresh 811A's for Christmas. I believe the maximum Plate Voltage that can be applied to these tubes is 1500 volts, vice the 1800 you applied. These tubes were tested in both by TV-7 and Amplitrex tube tester prior to listing. I used the Amplitrex results in the auction. None the less, with eBay, I have absolutely no repercussions.
  4. W1BR

    W1BR Ham Member QRZ Page

    I wonder what his B plus voltage was in his AL-811? Sounds like the seller is doing a song and dance routine--but eBay has you covered and he knows it. Once he admits he used them in an AL-811 and represented them as such, the 1500 volt max voltage claim is at best dubious.
    K1OIK likes this.
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    3 new tubes for your AL-811H ?
  6. K1OIK

    K1OIK Platinum Subscriber Platinum Subscriber QRZ Page

    I wonder what he did for the 4th?
    WG7X likes this.
  7. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    If you posted what the seller wrote verbatim, he didn't say he had an "H," he wrote "AL-811."

    The AL-811 or AL-811H produce 1700Vdc B+ normally (manual warns "not to exceed 1800V") but the 811A was always rated 1500Vdc maximum ICAS, so the design intentionally operates them above their ratings.
  8. W1QJ

    W1QJ Ham Member QRZ Page

    ANY decently made tube should be able to handle 300 volts over rating. A good tube should hi pot well over 2 times
  9. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I was unfamiliar with the tube tester the eBay seller said he definitely used to test his 811As for sale, an Amplitrex AT-1000.

    Specifications are below. It outputs a maximum B+ of 500V. That's insufficient to test anything about an 811A other than filament integrity and perhaps cathode emission.

    Attached Files:

    K1OIK likes this.
  10. K7MH

    K7MH Ham Member QRZ Page

    Depends on where it is installed and how soon you catch the leak.
    A couple years ago I was fine one day and the next no hot water. I went out to the garage where it was installed and there was water everywhere. It leaked a lot and all at once it seems! Even a small leak doesn't take long to empty the tank. It was a mess but nothing of importance lost to the "flood". It sure doesn't do any cardboard boxes that are on the floor any good!!
    Welcome to home ownership!!

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