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 Post subject: AK Model 20 Problem
PostPosted: Dec Mon 18, 2017 2:36 am 
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Location: Plymouth, MI
I have a restored AK Model 20 with good 01A tubes hooked up to a K101A battery eliminator with the proper voltages set. I've got a good ground and 60 feet of antenna (indoors). The reception is clear and sounds great with a pair of Little Tattlers, however, the volume is weak when I use an AK model L horn speaker or an AK E2 speaker. I've done the best I can tuning in this three dialer and increased the filament voltages with the rheostats, but still weak on the volume. This is the first time I've used the horn, it checks 1750 ohms. The E2 works great on my other AK's including a model 35 which I was working on just before the model 30. What's the problem?


Dan

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 Post subject: Re: AK Model 20 Problem
PostPosted: Dec Mon 18, 2017 2:58 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Bristol TN 37620
Dan,

If both of your speakers work OK with your other set, check the audio transformers.

Bill


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 Post subject: Re: AK Model 20 Problem
PostPosted: Dec Mon 18, 2017 3:46 am 
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Transformers checked good, but I will check them again Bill, thanks.

Dan

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 Post subject: Re: AK Model 20 Problem
PostPosted: Dec Mon 18, 2017 12:03 pm 
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Maybe a weak audio tube.

Might play louder with a 112-A instead of 01-A in the final (far right) audio stage.

Goose up the B+ voltage to the 2nd audio stage to maybe 135V (max.)

Reverse polarity of the speaker wires? (If the DC component of the plate current is fighting the direction of the magnet in the driver)


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 Post subject: Re: AK Model 20 Problem
PostPosted: Dec Mon 18, 2017 1:20 pm 
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Have you measured to see that you have normal plate and filament voltages at the audio tubes?
Also, you may have a bad solder connection at a tube base. As mentioned, perhaps a weak tube. Try moving an RF amp tube to the audio tube sockets and note any change.

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 Post subject: Re: AK Model 20 Problem
PostPosted: Dec Tue 19, 2017 4:57 am 
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Thank you all for your idea's. I will try your suggestions.


Dan

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 Post subject: Re: AK Model 20 Problem
PostPosted: Jan Mon 01, 2018 5:51 pm 
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Location: Keystone Heights, FL, USA
Did you ever get this one working?
Is it a compact or big box version?

Jeff


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 Post subject: Re: AK Model 20 Problem
PostPosted: Jan Tue 02, 2018 3:04 am 
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It's a big box Jeff. Had to set it aside for awhile while due to time constraints. I hope to get back to it in a couple weeks or so.

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 Post subject: Re: AK Model 20 Problem
PostPosted: Jan Fri 26, 2018 2:46 am 
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Looks like I need a better antenna. The AK 20 picks up my AM broadcaster loud and clear. I've had a similar issue with my ERLA radio so I will be installing an attic antenna in the next week or so.

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 Post subject: Re: AK Model 20 Problem
PostPosted: Jan Fri 26, 2018 3:40 am 
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Location: Maryland 20709, USA
Dan,

The E2 speaker (and its brethren) will not work with the 20.
You need a horn speaker having a DC resistance of about 2000 ohms.

The sound box in the L speaker is made of pot metal, which has likely come apart.
The only horn model with a steel sound box is the M.

- Leigh

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 Post subject: Re: AK Model 20 Problem
PostPosted: Jan Fri 26, 2018 3:56 am 
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Leigh, I fired up the AK 20 earlier tonight with an Edison-Splitdorf speaker horn.

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 Post subject: Re: AK Model 20 Problem
PostPosted: Jan Fri 26, 2018 6:11 pm 
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Make sure that the grid resistors on the first (left) tubes are OK. These are the flat fine wire resistors mounted on the backs of the tuning condensers. They are very often open and easily replaced with modern resistors.

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 Post subject: Re: AK Model 20 Problem
PostPosted: Feb Fri 09, 2018 3:27 am 
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Problem solved. My new attic antenna wire is installed and what a difference! My Big Box 20 is playing loud and clear. Thank you all for your input on this issue.

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