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.
You now have no bias so the tubes will run very red. You are running idle
current right at the maximum dissipation ratings of the tubes.
The zeners should check out as a regular diode on an analog VOM. They
can be replaced with a reverse connected string of 1N5408's.
>
>Also, the grid current meter is reading backwards, ie, pegging in the
>left
>hand direction, or below zero.
May be a shorted tube, try one at a time. However that grid current
circuit does require a level of bias to zero out the meter.
I have repeatedly called the AL-82 a firecracker amp, you are just
another victim.
>
>Our brains are mush and we are going to bed.
I just woke up.
73 Carl KM1H
>
>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
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>http://www.contesting.com/km9p/search.htm
>> >
>> >
>>
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>
>--
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>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 http://www.juno.com/getjuno.html
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Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
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