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 Post subject: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Sat 22, 2019 1:28 pm 
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Location: Cheyenne, Wyoming, USA
I have had this little receiver for years and I want to get it going. I am trying to find a TM or a service manual for it. can anyone help. For a circa 1943 radio it seems like a pretty good one. Its receive range is 2300Kc to 6300Kc.

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 Post subject: Re: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Sat 22, 2019 4:23 pm 
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There is a semi-usable copy on the BAMA manuals download website as part of the AVT-15 set. Or, you can buy a copy from several manual vendors.

I have one of these in the stack awaiting restoration. Obviously, all the wax capacitors need to be replaced and some of them are really crammed in there. These are getting harder to find at a decent price because the non-radio-hobbyist aircraft "restorer" people are seeking these for WWII era light aircraft "spotter" plane rebuilds. Unfortunately as often as not, they gut the innards from this equipment to save weight and it becomes a "static display."

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 Post subject: Re: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Sat 22, 2019 4:29 pm 
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The March 2019 issue of "Electric Radio" has an extensive article on the AVR-20-A1. It is a must-read article for anyone attempting a restoration on one of these sets.

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 Post subject: Re: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Sat 22, 2019 4:34 pm 
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https://www.qsl.net/ab0cw/AVT_AVR.htm

The matching transmitter is a cutie too!

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 Post subject: Re: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Sun 23, 2019 1:58 am 
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Location: Green Bay, Wi
It is a very nice example of a small radio from that era. It works quite well and the oscillator can be adjusted so the unit will cover the 40 meter band as well as 75/80 meters. The only difficult part is pulling and restuffing the can with the capacitors in it, not really too bad just keep track of what goes where and all will turn out okay. This is what I used though out my novice days in mid '50's as it was quite cheap and money was really hard to come by. That and a 6L6/6V6/6Y6/6F6 whatever I could come by with a crystal and couple condensers plus a coil were my station. Power supply from a defunct TV set and an antenna made from AC zip cord. Boy how things have changed for the folks starting out now. BUT it was really fun and exciting.


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 Post subject: Re: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Sun 23, 2019 3:34 am 
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Peter Bertini wrote:
https://www.qsl.net/ab0cw/AVT_AVR.htm

The matching transmitter is a cutie too!


I have the matching transmitter. I have not really looked it over once I get done with this receiver all take a look at it.

Looking for my issue of the March 2019 ER right now.


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 Post subject: Re: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Sun 23, 2019 4:41 am 
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Here are photo's of my radio. As you can see it is completely unmolested


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2E260870-BE32-4155-A08A-73A719CDFBF7.jpeg
2E260870-BE32-4155-A08A-73A719CDFBF7.jpeg [ 461.46 KiB | Viewed 582 times ]
E6124EB4-B0C6-4772-BE9D-886C7F1FA090.jpeg
E6124EB4-B0C6-4772-BE9D-886C7F1FA090.jpeg [ 387.67 KiB | Viewed 582 times ]
1F1DB83E-B677-4025-88FD-D1753586494E.jpeg
1F1DB83E-B677-4025-88FD-D1753586494E.jpeg [ 494.52 KiB | Viewed 582 times ]
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 Post subject: Re: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Mon 24, 2019 6:22 pm 
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Found the manual here :http://www.vmarsmanuals.co.uk/archive/5055_RCA_AVT-15_Aircraft_Transmitter.pdf

looking at the System I see that

The manual covers:
Transmitter: AVT-15, and 15A
Receiver: AVR-20-A1
AntennaSystem: AVA-120


Attachments:
0F6AB2AE-621A-4861-B17F-F668F06B8486.jpeg
0F6AB2AE-621A-4861-B17F-F668F06B8486.jpeg [ 177.82 KiB | Viewed 504 times ]
CE565F59-D3FA-4000-AC13-6A6A5AE0A98F.jpeg
CE565F59-D3FA-4000-AC13-6A6A5AE0A98F.jpeg [ 182.17 KiB | Viewed 504 times ]

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 Post subject: Re: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Fri 28, 2019 3:07 pm 
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looking through the manual for this radio and I notice it shows a 250 volt plate voltage. The radio is listed to use 12VDC. Does this receiver take its power from the AVT-15A transmitter? It has a vibrator that supplies such voltages.

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 Post subject: Re: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Sat 29, 2019 2:44 am 
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Location: Monterey California USA
In the case of use with the AVT-15 transmitter, yes, the high voltage is supplied from the transmitter internal supply. However, I suspect the AVR-20 was more frequently found paired with the AVT-112 transmitter, and then there was a separate power supply for both. Number escapes me...AVA-126? Something like that. RCA was preoccupied with using their proprietary octal based vibrator in this equipment and today those vibrators are totally extinct.

Since you only have the receiver, you will need to make a 200-250V power supply. Pretty simple, actually.

I remembered why I haven't gotten my receiver running yet. I lost motivation when I realized I would have to re-stuff that can that has the capacitors in it. I know it isn't that big a deal but I found something more exciting to work on and the receiver is still in the best intentions storage room.

The VMARS manual on line is simply awful. Better than nothing and free, but...ugh. There is more to making a decent printable pdf of a manual than just sloppily scanning pages and then uploading them.

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 Post subject: Re: RCA Model AVR-20-A1 (MI-5978A) Aircraft Receiver
PostPosted: Jun Sat 29, 2019 4:15 am 
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I think the transmitter is an AVT-112. This has sort of given me pause as well. That can has 7 capacitors in it. I have a ZTO Royal 1000 that needs alignment, and a Royal 3000-1 that also needs alignment, and check as to why it's FM doesn't work. Pretty sure it is a coupling capacitor I have not replaced yes.

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