[Collins] 32V-1

[Jim Brannigan]

If the relay failed to energize, how did the TX terminal connect to the RX 
terminal?  At worst the TX would transmit into an open load...

Jim


> The 75A1 uses a common input transformer/coil on all bands. The secondary 
> is fed to the individual band coils.
>
> Bad DowKeys is one reason I switched to a regular open frame relay ages 
> ago for my boatanchors. If the VSWR is high up on 10M its easy enough to 
> tune out with a compression trimmer at low power, measure and then replace 
> with a 1KV mica or disc for up to several hundred watts.
>
> Carl
> KM1H
>
>
>
>
> ----- Original Message ----- 
> From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
> To: <collins at mailman.qth.net>
> Sent: Sunday, December 16, 2007 2:38 PM
> Subject: Re: [Collins] 32V-1
>
>
>> On Sun, 2007-12-16 at 09:00 -0500, Phil LaMarche wrote:
>>>  This morning my dowkey relay failed and didn't mute the 75A-1.  Quickly
>>> unkeyed but smoke rolled out of the receiver and no audio.
>>>
>>> Guessing the ant coils smoked but won't know till looked at.  Can anyone
>>> advise if these coils can be found anywhere>  I had a SB221 in line as 
>>> well.
>>>
>>> Phil
>>>
>> Ought to be only one antenna coil smoked. Just for the one band. Just
>> failing to mute shouldn't have done in the receiver, unless the
>> transmitter arced across the open RF contacts to put RF on the receiver
>> (and antenna) directly.
>>
>> One smoked antenna coil shouldn't kill receiver audio or other bands
>> unless continued audio feedback overworked the audio output tube or
>> audio output transformer, but I've seen 6V6 screens glow red without
>> permanent damage.
>>
>> It may take good archeology to determine the construction of the
>> original coil, probably low frequency and PI wound?  Likely its a
>> variation on a stock slug tuned coil from a place like J.W. Miller with
>> a custom inductance and an antenna link winding. Extracting the smoked
>> coil from the radio while leaving enough to do that archeology will be
>> the trick.
>>
>> -- 
>> 73, Jerry, K0CQ, Technical Advisor to the CRA
>> All content copyright Dr. Gerald N. Johnson, electrical engineer
>>
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>
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