[AMPS] AL-82
Roy Koeppe
royanjoy@ncn.net
Sun, 17 Jan 1999 08:40:54 -0600
I agree with below... I have seen it many times with warped grids in
3-500Zs, before I remedied the parasitics problems.
73, K6XK
-----Original Message-----
From: Mark S Graalman <wb8jkr@juno.com>
To: michon@eatel.net <michon@eatel.net>
Cc: km1h@juno.com <km1h@juno.com>; amps@contesting.com <amps@contesting.com>
Date: Sunday, January 17, 1999 5:47 AM
Subject: Re: [AMPS] AL-82
>
> 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
>>> 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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>>
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>>
>
>___________________________________________________________________
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