[Collins] 32V-1

[jeremy-ca]

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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