[R-390] R-390 Digest, Vol 84, Issue 11

[bernie nicholson]

Hi To all   regarding Litz wire in IF Transformers , I recently was 
Re-aligning an IF  in  a Racal RA17  and wasn't able to get anything like 
the band pass characteristics that I know they are capable off , upon 
further investigation , after removing the transformers I found that over 
many years of heating cooling  cycles some of the strands  of litz wire had 
gone open circuit at the terminations after running more solder  into the 
Terminations  and burning off the enamel A normal bandpass characteristic 
was achieved  , and this receiver had also been very noisy ,lots of 
extraneous clicks ect , This stopped after the treatment , Also recently I 
had a 390A with a very noisy IF module  That was similarly afflicted  with 
noise clicks , this was traced to an insulation breakdown of the foam in one 
of the Mechanical filters ,it measured 150K Ohm to the case when Meggar 
tested , after replacing the filter it was nice and quiet , Quiet often I 
find that  Litz Wires within IF transformers are Terminated under tension , 
and after many years of heating and cooling Metal fatigue sets in and they 
are open circuit   Or Partially open circuit as previously noted    Regards 
to all Bernie VK2ABN
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Sent: Wednesday, April 06, 2011 2:01 AM
Subject: R-390 Digest, Vol 84, Issue 11


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>   1. Re: 16 KHz filter oscillates (Barry)
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> Message: 1
> Date: Tue, 5 Apr 2011 08:46:57 -0400
> From: Barry <n4buq at knology.net>
> Subject: Re: [R-390] 16 KHz filter oscillates
> To: <R-390 at mailman.qth.net>
> Message-ID: <51978.1302007617 at knology.net>
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>> I do not see any striped wires about the filter sections. This is a later
>> production and most of the wires are dressed in plain pastel. Some are in
>> see thru translucent white. Nice silver body wire. Still no tarnish / tan 
>> /
>> rust.
>
> You obviously have the only known example from the infamous Helena 
> Rubenstein collection.  Congratulations!
>
> Barry - N4BUQ
>
>
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> End of R-390 Digest, Vol 84, Issue 11
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