[R-390] Re: Z503

[Gord Hayward]

Mine had a similar problem and unfortunately I killed the coil when I 
tried to fix it.  The winding is potted in
goo (not ukumpucky) and the ferrite is on the outside of the coil too.  
When I tried to get the coil apart with
heat I really did it in.  So, I took a honking big coil from my junk box 
and a small cap and rebuilt it.  It peaks
and the set performs at spec now.  The trick was to use a big coil to 
get a high enough Q which determines
the impedance of the parallel resonator and hence the stage gain at 
resonance. (big L, small C = big Q)

>Along  the way I managed to destroy Z503 so I pulled one out of a 'cadaver' 
>IF  strip.  I noted that it's slug is fairly well centered in the core.   
>Upon replacing Z503, the 'new' one behaved the same way.... increasing  stage 
>output as the slug was cranked toward the top but it runs out of  adjustment 
>before peaking.
>
Cheers es 73 de Gord, VE3EOS

-- 

Gordon L. Hayward, Ph.D., P.Eng.,
Associate Professor, Biological Engineering,
School of Engineering, University of Guelph,
Guelph, Ontaro, N1G 2W1.