On Sunday, 3 December 2017 14:41:50 UTC, N_Cook wrote:
On 03/12/2017 12:54, Cursitor Doom wrote:
I've had this great old classic radio for the best part of 40 years and
it's always sounded great on the FM/VHF band until recently. Now I'm
finding it increasingly difficult to tune-in properly, even with strong
stations. It just sounds a bit scratchy like it's off-frequency slightly.
The usual leeway I got with tuning a station has gone; it has to be dead-
on yet it's still not quite right. Speech can often sound totally fine,
but when there's a musical interlude the problem suddenly becomes
apparent again. Is this symptomatic of it needing a re-alignment? I can't
think what else could be causing it, but since I've never experienced
such a problem before, I'm really pretty much in the dark here. Any ideas?




If you do start twiddling IF Tx cores , mark the angle and measure the
depth of each, making up a little nut and screw "depth gauge" and only
try 1 at a time , so you can get back to where you started from.
Another consideration, any ceramic resonator filters perhaps not 40
years back, the silver inside can migrate over the resonator edges and
make them go ohmic, losing selectivity

SAW filters got into consumer goods in the 80s. It'll be cans with slugs.

the following is more from reading than experience...
Before doing any twiddling you really need to know the set up technique, it was not as simplistic as twiddle for best volume/clarity. AIUI the slugs were stagger tuned to get the best shaped response, fail to follow that method and you'll end up with really crap audio frequency response for AM, for FM I presume lousy signal capture & distortion.


NT