Ameritron AL-811H just went pop

Discussion in 'Amateur Radio Amplifiers' started by NI2M, Oct 11, 2021.

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  1. NI2M

    NI2M Ham Member QRZ Page

    Forgot to mention that just prior to the wide-band noise appearing I heard a very muted “snap” like sound from the amp…..
     
  2. N8VIL

    N8VIL Ham Member QRZ Page

    My 811A amplifier (3 tube) would do this in standby if I recall correctly. About 7-8 years ago. I had receiver noise and an occasional low snapping noise. I believe the tubes were not fully cutting off in standby. I performed a remote cutoff modification and added gas discharge tubes which solved my problem.
    Here is a link to the modification I did along with some information on 811 tubes.

    811A tube 572B tube history
     
    Last edited: Oct 18, 2021
    N3RYB likes this.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Of all the amps Ameritron has made, the 811/811H is the most problematic.

    I'd fix it and dump it.:)

    When an amp generates wideband noise (RFI), either something is arcing internally or the tubes aren't cut off. If it's a bias problem (tubes not cut off), you should have seen plate current indicated on the panel meter which of course should read "0" in standby.
     
  4. N3RYB

    N3RYB Premium Subscriber QRZ Page

    Also if you are going to be on W8JI's page, might as well have a good look at the AL-811 reliability mods as well. https://www.w8ji.com/al811_important_modifications_changes.htm
    They're all fairly easy to do and are noted to resolve the problem described as well.
     
    KA0HCP likes this.
  5. NI2M

    NI2M Ham Member QRZ Page

    I didn’t see any plate current whatsoever. So perhaps this is “merely” an internal arcing problem.

    The amp has served me pretty well for what it is, a garden-variety deal. I may get a new amp in future but as it is pretty difficult to get 240 V to my shack I am limited in terms of RF power out. I like Alphas but I am not sure if running them off of 120V works well. Max 600W is what I have put out and with general band conditions starting to improve soon that power level is plenty.
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    An AL-80B can operate normally from a 120V outlet, but best if it's the only thing on that circuit (branch) and nothing else consuming much power shares that line.

    At 600W output, it should last forever.:p
     
  7. NI2M

    NI2M Ham Member QRZ Page

    Appreciate all the pointers and suggestions!
     
  8. NI2M

    NI2M Ham Member QRZ Page

    I like the Kenwood TL-922A but by default they don’t come with 1o meters. An Alpha 87A is for sale locally here in Texas which intrigues me.
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The AL-80B covers 160 through 10 meters, weighs less than the 922A and runs almost as much power. They all ship with all 10m/12m circuitry included, you just "activate" it, which takes about ten seconds.:)

    The 87A is a very good amplifier but I'd be really careful: The amp is about 50% control systems, including a microprocessor and lots of "intelligence" and that's the part that fails -- way more often than the PA circuitry or power supply; but if it ever needs new tubes, 3CX800A7s can cost $1000 each today...and maybe more than that. Can go from a great working amp to a paperweight in one day.

    -Former 87A owner.:p
     
    KW6LA likes this.
  10. NI2M

    NI2M Ham Member QRZ Page

    OK on the AL-80B.
    87A (and others of that ilk); you are reading my mind. I do see the MTBF getting shorter and shorter the more “cool features” the amp has. I have been looking at the Mercuri IIIS as well. Only thing is that unless you have an ATU the solid state amp will get its output folded back considerably.
    Took my AL-811H to Array Solutions this morning as it is a local company and I have heard that the quality of their service is really great. Jay, the owner, showed me an ACOM 1000 amp (it has a ceramic tube in it) that looks fairly “garden variety” (it does have a microprocessor board in it) that he is selling.
     

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