wrote in message
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https://dl.dropboxusercontent.com/u/...6/tunerwtf.jpg

That's a Sansui TU-7500

This is a matter of curiousity. Off the secondary of T301 there are two
totally unmarked devices circled in red. If they were diodes I guess they
would double the frequency but I see no need for that in an AM front end. If
the secondary is center tapped and those two parts are identical, then there
would be no output from the mixer to the IF.

If they are not identical, I suppose they could be some form of impedance
matching. It does seem though on a manufacturing scale like Sansui had back
then they could just get the transformer they wanted. Maybe one is a
bandpass and the other a bandstop ?

Seems like they would say something about it in case a replacement is
needed. It is not indicated at all whether they are under the transformer
shield or anything, but such things are indicated in the FM section.

The reason I even saw this is because one is about to come across my bench.
But I get curious when things do not make sense.

I understand people wanting to hide their proprietary goodies and all that.
In fact I kinda like the way the AGC is set up in this one. But secrecy for
an AM tuner ?

Any thoughts ? Like I said it is just curiousity but then again curiousity
is what got us all into this mess...

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Crystal filter.