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 Post subject: Allied A-2515 questions
PostPosted: May Fri 31, 2019 12:43 am 
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Location: North Carolina
Why do I have to keep the RF gain turned up to the max to be able to hear anything? If I turn it down just the smallest amount the sound goes away.


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 Post subject: Re: Allied A-2515 question
PostPosted: May Fri 31, 2019 3:03 am 
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Location: Ohio 45177
The RF gain is a pot across the antenna input system. I had the opposite problem with mine. A fully efficient full sized dipole on say, 40 meters was unable to reduce the signal levels very much in that receiver. Perhaps there was parasitic RF coupling around or thru the pot with the strong signals from a resonant antenna. OR maybe the fact I installed a 40673 MOSFET RF amp to replace the blown mosfet was an issue as it might have been higher gain. They should have used their RF gain control to adjust bias on one of the gates of the RF mosfet amp instead of that wretched pot across the antenna scheme. Did you make sure your antenna protection diodes were good? I cannot really go back and check much as after I loaded the manual onto a disc for the one I sold, I deleted it from my archives.

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 Post subject: Re: Allied A-2515 question
PostPosted: May Fri 31, 2019 3:11 am 
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I will have to check the diodes


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 Post subject: Re: Allied A-2515 question
PostPosted: May Fri 31, 2019 11:37 pm 
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Since the diodes are back to back across the antenna terminals, they will read between .2 and .5 volts drop each way in a diode test. Not short circuit. Presumably they were put in to prevent blowing the mosfet from static discharge or too much RF from a transmitter.

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 Post subject: Re: Allied A-2515 question
PostPosted: Jun Wed 05, 2019 2:15 am 
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Location: North Carolina
I am guessing check the diodes with the power off correct?


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 Post subject: Testing a non-working S-Meter
PostPosted: Jun Wed 05, 2019 2:29 am 
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Joined: May Thu 09, 2019 12:06 am
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The one on my Allied A-2515 does not work. Is there way to test to see if it is the meter or something else causing it not to work?


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 Post subject: Re: Testing a non-working S-Meter
PostPosted: Jun Wed 05, 2019 2:46 am 
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I took the meter out of my CB and used a 1k resistor and a current limited power supply to test the swing on my s meter.

I think you could probably use a battery and a potentimeter to do the same thing.

Jason

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 Post subject: Re: Testing a non-working S-Meter
PostPosted: Jun Wed 05, 2019 2:52 am 
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Greetings to rhrailfan and the Forum:

Yes. I was unable to download more than the schematic on the internet, but at a guess from the component values, the meter is a 0-1 mA meter.

Disconnect the meter leads from the radio circuitry. Place a 10K resistor in series with a 9 volt battery and connect across the meter terminals. The meter should deflect to near full scale. (If it deflects backwards, you have the polarity wrong.)

Regards,

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 Post subject: Re: Testing a non-working S-Meter
PostPosted: Jun Wed 05, 2019 3:52 am 
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Location: North Carolina
Thank you for the info


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 Post subject: Re: Allied A-2515 questions
PostPosted: Jun Thu 06, 2019 2:00 am 
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The manual and schematic pdfs are on BAMA but they are listed under Knight instead of Allied. Has part number of meter but not the value.

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 Post subject: Re: Allied A-2515 questions
PostPosted: Jun Thu 06, 2019 3:22 am 
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I plan to check the meter and diodes out this weekend. Once I get my listening spot setup this will be my main radio until I get one of my Hallicrafters redone. So I want to get it working right. I wish there were some mods to make it even better.


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 Post subject: Re: Allied A-2515 questions
PostPosted: Jun Fri 07, 2019 7:44 pm 
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Well if it is an early version with the narrow filters that muffle AM stations, you could modify it to the later configuration where they broadened the selectivity to make AM modulation reception clearer. I think they just removed one or more of the ceramic filters. I would have to see the schematics side by side, I think both versions are out there.

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 Post subject: Re: Allied A-2515 questions
PostPosted: Jun Fri 07, 2019 11:17 pm 
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How could I tell which version I have?


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 Post subject: Re: Allied A-2515 questions
PostPosted: Jun Sat 08, 2019 2:37 am 
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Location: Ohio 45177
I found this information searching: https://www.radiobanter.com/shortwave/6 ... -rcvr.html
This guy claims that the later version with the wider IF for AM was called an A2515A.
The narrow IF version has four metal cans on the IF strip at the back of the radio, marked MF-1 thru 4.
This guy says they reduced it to two cans of ceramic filters. And removed one gain stage. I would think they would have used the same circuit board and just left the holes unused for the extra parts instead of going to the expense of designing a new board layout for a unit in production. Well you can tell if AM signals sound muffled a bit with no high tones.

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