[AMPS] AL-82

[Mike Michon]

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
> 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
> >
> >
> >--
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> >
> >
> 
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