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AL-811 does not load anymore...?

Discussion in 'Amplifiers' started by Nick-PP8DA, Mar 7, 2011.

  1. Nick-PP8DA

    Nick-PP8DA Member

    Feb 24, 2011
    Likes Received:
    Hello All;
    I have purchased several days ago a used AL-811 amp serial AL811-14519,sold originaly by AES-in Orlando.The amp is several years old and is way different from the ones pictured actually.He was working fine,as long as tuned with input drive not bigger as 40 Watts with gave an output aroud 400 W.Several days ago I conected him to a 1KW dummy and started tuning him with 70 W drive, initially he gave 550 W out but suddently an arc some place and the Svetlana? Chines? tubes colapsed the internal plate sheet and went imediately dead.A further inspection reveled that the input band swith slector located on PCB P/N#862-0811-1 Rev.3 overheated and the sliding contacts bended away.I tried to repair them into the correct position but due to the heat they lost their spring contact ability.The switch looks like overheated.In a short test with 20 W drive it renedred no success and to save the new 811Taylor´s, I stoped everything. More information: input voltage is 230 V, Hv reading 1.700 Volts, IP idling is _+ 50 mA (does not accept any load)and the grid is aroud 50 mA in the present situation.Presently,as soon as you try to load the amp it starts to red the tubes, so I have disconnected the amp to save the tubes.

    That is the story from this end.

    I orderd from Ameritron a new wafer switch and several high voltage disc caps in the high voltage area, before and after the choke, the plate 7.5 Kv disc cap for safety to replace.

    The main RX/TX relay showed a small spot and I carefully cleand this contact.
    I am waiting for MFJ to find and quote one for me,they have it in their catalouge.Keep waiting.

    It is very difficult to deal with Ameritron as they simply do not ansver to problem inquieries, fortunately my dougther was eable to contact Ameritron with the spare parts.

    If some one kindly give me a hand in a more advanced expertise to find the problem, I will be very gratefull.
    Sorry for my bad english writing, please excuse.

    best regards and 73


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