[R-390] Open Z-503 AGC IF Transformer

[JMILLER1706 at cfl.rr.com]

Believe it or not I have rewound RF/IF transformers like this that have 
been fried.  If you can unravel the turns, just measure the total 
length after getting the wire off, go buy some small diameter magnet 
wire of the same gauge and length, or close, and wind it back on.  It 
won't look pretty but it will probably work.  Glue or wax to hold it in 
place.  I did that with an RF coil in a 51S1 once.  Worked great.  
Alternately, it is possible that a coil from generic 455 khz IF can 
would work.   JM

----- Original Message -----
From: Gord Hayward <ghayward at uoguelph.ca>
Date: Tuesday, January 10, 2006 8:38 am
Subject: Re: [R-390] Open Z-503 AGC IF Transformer

> >
> >
> >I am looking for a replacement if anyone has one.  Pulled it 
> apart but it is
> >open somewhere inside the windings, usually it is around the 
> connections.>Anyway, hoping someone can help.  As you know it is 
> not an easy guy to get
> >to. ... Tom, N3LLL
> >
> 
> When I got mine, Z503 was open too.  I tried to steam (hot air 
> really) 
> the ferrite off but the whole thing
> came undone.  Not finding a replacement, I took a big coil out of 
> my 
> junque box, cut the form to fit,
> added a resonating cap at 455 kHz and rebuilt the guts of the can. 
> Now 
> its dead on spec.
> 
> The trick is to use a small cap, 20 to 40 pf or so to get the Q as 
> high 
> as possible.  That circuit needs
> the high Q to get the AGC voltage high enough.  Do the resonance 
> check 
> before the cutting and
> installation steps.
> 
> -- 
> 
> Gordon L. Hayward, Ph.D., P.Eng.,
> Associate Professor, Biological Engineering,
> School of Engineering, University of Guelph,
> Guelph, Ontaro, N1G 2W1.
> 
> 
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