Sounds like a filament to grid short to me.
Mark WB8JKR
On Sat, 16 Jan 1999 22:44:19 -0800 "Mike Michon" <michon@eatel.net>
writes:
>
>Replaced the diode on circuit board, it was on schematic, and was bad.
>Replaced with a IN4141 because that was all I had. No difference in
>the
>wild red glowing of plates.
>
>Checked zener diodes in center tap of filament transformer. Red lead
>of
>meter to threaded post of zener diode #1 .559 mega ohms. Reversing
>leads
>1.35 mega ohms.
>
>Zener #2 red lead of VOM to threaded post 1.4 mega ohms. Reverersing
>leads, 14.1 mega ohms.
>
>Running amp with zeners disconnected, still big red glow and 300 ma on
>plate current meter.
>
>Also, the grid current meter is reading backwards, ie, pegging in the
>left
>hand direction, or below zero.
>
>Our brains are mush and we are going to bed.
>
>Thanks for your reply.
>
>Mike Michon
>AB5XP
>
>----------
>> From: km1h@juno.com
>> To: amps@contesting.com
>> Subject: Re: [AMPS] AL-82
To: <amps@contesting.com>
>> Date: Saturday, January 16, 1999 5:05 PM
>>
>>
>>
>>
>> On Sat, 16 Jan 1999 18:26:18 -0800 "Mike Michon" <michon@eatel.net>
>> writes:
>> >
>> >I have an AL-82 amp that was doing OK till yesterday. I turned it
>off
>> >and
>> >on quickly yesterday morning. It was 4 am and I was half asleep, so
>I
>> >don't
>> >know why I did it.
>> >
>> >A line fuse blew. I replaced it. Now the amp plates start glowing
>> >red, as
>> >if drive is applied, with antenna out of tune or not properly tuned
>
>> >up.
>> >
>> >A visual inspection reveals nothing obviously cooked or fried.
>> >
>> >A 1 hp motor connected in series with the 220 volt input to HV
>> >transformer
>> >drops the HV to 800 volts so we can observe it a while longer. The
>
>> >motor
>> >stays in Locked rotor indicating a heavy load from the plates being
>
>> >in
>> >conductivity.
>> >
>> >Any ideas as to what is going on?
>>
>>
>> For starters:
>>
>> Replace the diode on the PS board that is not designated on the
>> schematic. It is a 1N4001 between the B- rail and real ground.
>Replace
>> with a 1N54x series.
>>
>> That is a very common AL82 failure mode that also destroys tubes,
>blows
>> suppressors, etc. At the very least I would install a 20 Ohm 20W WW
>> resistor in series with the HV lead.
>>
>> Ameritron/MFJ will not admit to any problems so dont waste ur time.
>Sorta
>> like dealing with Henry !
>>
>> I'm off for the eve/night but let me know ur results...will be back
>tmw.
>>
>> 73 Carl KM1H
>>
>>
>>
>> >
>> >Mike Michon
>> >AB5XP
>> >
>> >
>> >--
>> >FAQ on WWW: http://www.contesting.com/ampfaq.html
>> >Submissions: amps@contesting.com
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>> >Problems: owner-amps@contesting.com
>> >Search: http://www.contesting.com/km9p/search.htm
>> >
>> >
>>
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>
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>
>
___________________________________________________________________
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Get completely free e-mail from Juno at http://www.juno.com/getjuno.html
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Problems: owner-amps@contesting.com
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