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 Post subject: Magnavox Amplifier 1920's
PostPosted: Feb Mon 12, 2018 3:40 am 
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I can't seem to find out much about this amp. Does anyone have any information on it and possibly a schematic? As always, all help is greatly appreciated.



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Magnavox Amp-e.jpg
Magnavox Amp-e.jpg [ 230.78 KiB | Viewed 1031 times ]

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Dan

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Last edited by atwaterkent1 on Feb Sun 25, 2018 3:30 am, edited 1 time in total.

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Mon 12, 2018 4:34 am 
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Looks like a Magnavox AT-3. Google that model and you should find out a lot more about it.

GL,

Terry
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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Mon 12, 2018 4:39 am 
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Hello atwaterkent,
what great amp


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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Mon 12, 2018 4:47 am 
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Thanks Radiorich.

I believe it is an AT-3 model C. Thanks Terry!

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Tue 13, 2018 9:47 pm 
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There's an AC3 too ...


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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Wed 14, 2018 12:02 am 
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Why the two key slots on each tube socket?

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Wed 14, 2018 12:37 am 
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So that VT-2 (205D) tubes could be used in the amplifier if desired.

Norman

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Wed 21, 2018 12:56 am 
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Still haven't found a schematic or information on the AC3C I've acquired. I know the filament voltage is 6V but I don't know what the B voltage is. Doe anyone know anything about the amp?

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Last edited by atwaterkent1 on Feb Wed 21, 2018 2:25 am, edited 1 time in total.

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Wed 21, 2018 1:50 am 
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Recommended B+ voltage is 67, Dan, but it will also work with either 45 or 90.

-- Grant


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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Wed 21, 2018 2:24 am 
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Thanks Grant. Do you have one? How did you know?

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Wed 21, 2018 2:40 am 
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One more question please, what are the "field" connections for?

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Wed 21, 2018 3:53 am 
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The Magnavox Telemegaphone speakers including the R2 and R3 had field coils rather than permanent magnets. The speakers field coil would hook up to the "field" posts on the amplifier.

Norman

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Wed 21, 2018 3:56 am 
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Thanks Norman for helping me with my ongoing education here at the Forum!

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Wed 21, 2018 11:25 am 
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atwaterkent1 wrote:
Thanks Grant. Do you have one? How did you know?


I don't have one at the moment, Dan, but I have had several AC-3's (and AC-2's) in the past. They're great early amplifiers. Beautifully made, too.

-- Grant


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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Thu 22, 2018 3:09 am 
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I agree Grant, it looks so much better than the typical 20's amp. Finally had time to go through the amp and it all looked great, so time to try it out. Wired it up to my Radiola III and it worked great, all three stages. One of my better acquisitions.

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Radiola 3 & A3C3.jpg
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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Sun 25, 2018 3:08 pm 
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Did you have a problem with AC hum?

Regards,
Donald

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Feb Sun 25, 2018 10:13 pm 
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Not at all Donald.

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Dan

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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Mar Sat 03, 2018 5:29 am 
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Hello Dan,
glad to hear it works great that would be a cool design to build a repo amp I love that design layout
very cool


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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Mar Sat 03, 2018 1:37 pm 
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I have worked with guys from ITT/Exelis in Fort Wayne, Indiana. Some of their parents had worked for Magnavox and we had interesting talks of how these premium electronics companies rose and fell. I've had friends who worked for Stromberg-Carlson here in Rochester.
Triode amplifiers are sought by some purists as having the best sound.
Magnavox was able to get away from the RCA/DeForest Audion patent on some of their tubes by designing them differently enough to circumvent the patent.
An interesting AWA article here:
http://www.antiquewireless.org/uploads/ ... a_tube.pdf


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 Post subject: Re: Magnavox Amplifier 1920's
PostPosted: Mar Sun 04, 2018 8:59 pm 
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Thanks radiorich! You too Wally58, great link.

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