Checked the tubes for filament to grid short. One tube was shorted from
filament to grid.
Hooked tube from filament to grid to a 12 volt car battery and burned
shorted parts off. The tubes put out 1200 watts again. For how long we will
see.
Thanks for the information.
Mike Michon
AB5XP
Technical information about tube repair method from Richard WA5NYG
----------
> From: Mark S Graalman <wb8jkr@juno.com>
> To: michon@eatel.net
> Cc: km1h@juno.com; amps@contesting.com
> Subject: Re: [AMPS] AL-82
To: <amps@contesting.com>
> Date: Sunday, January 17, 1999 3:45 AM
>
> 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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> >> >
> >> >
> >>
> >> ___________________________________________________________________
> >> You don't need to buy Internet access to use free Internet e-mail.
> >> Get completely free e-mail from Juno at
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> >>
> >> --
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> >>
> >
> >--
> >FAQ on WWW: http://www.contesting.com/ampfaq.html
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> >
> >
>
> ___________________________________________________________________
> You don't need to buy Internet access to use free Internet e-mail.
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