[R-390] Subject: Re: R-390 Audio Transformer

[rbethman]

Group,

I bought about 5 or 6 of those Radio Shack PA Transformers.

Still have several in their bubble pack.

On the Audio Output of R-390A, use C, (Common), and 2.5W for input.

The Speaker side - C, (Common), - Then the impedance of speaker being 
used, 4, 8, or 16.

Bob - N0DGN



On 4/22/2012 7:48 AM, Steve Hobensack wrote:
> Mike,
> My TCS rx uses C and 0.62 watts for primary and c&  16 ohms to the speaker voice coil found experimentally. I don't remember the connections on the R-390 because I use the filament transformer. You can find it experimentally by listening for best/loudest sound by ear or you can use a Simpson 260 VOM on A/C. Put the R-390 on calibrate with a 1000 cps tone output, look for max volts on the speaker.
> Steve N8YE
>
>> Message: 4
>> Date: Sat, 21 Apr 2012 07:36:18 -0700 (PDT)
>> From: Michael OBrien<mikobrien at yahoo.com>
>> Subject: Re: [R-390] R-390 Audio Transformer
>> To: Steve Hobensack<stevehobensack at hotmail.com>
>> Cc: "r-390 at mailman.qth.net"<r-390 at mailman.qth.net>
>> Message-ID:
>> <1335018978.67779.YahooMailNeo at web130206.mail.mud.yahoo.com>
>> Content-Type: text/plain; charset=iso-8859-1
>>
>> Hi Steve
>> I have 1 or 2 of the RS 70v line transformers Do you remember what taps to use?
>> Mike
>>
>>
>>
>> ________________________________
>> From: Steve Hobensack<stevehobensack at hotmail.com>
>> To: r390 reflector<r-390 at mailman.qth.net>
>> Sent: Saturday, April 21, 2012 10:17 AM
>> Subject: Re: [R-390] R-390 Audio Transformer
>>
>>
>> An 18 volt filament transformer will do the same thing as the more expensive audio transformer. 120 to 18v is the ratio for maximum power transfer that I found experimentally.? Radio shack used to sell them. I don't know if they still do. I don't know about the frequency response though. I also compared it to a multi-tapped 70 volt line to voice coil transformer, and my ear couldn't tell the difference.
>> Steve N8YE
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