I am working on a STA-90 Realistic Receiver from the old days.
it had - voltage reg problems that is resolved how ever,
i noticed that the receiver is not very good on signal level
strength and as i tune between the stations on FM i am picking up
out of band digital sounding noise that i think the IF is picking due
to insufficient drive of the desired band to staturate the IF.
in aways, after testing this and that i thought maybe the front end
transistors (MosFets) may have been bad. but after checking signals with
Ger, RF vm i noticed that i am getting a great loss through the dual
ceramic filter network for the FM if? ., i don't have a real service
print on this so i don't know what i actually should be getting but the
print i do have does give my DC volts et.c.
Anyways, is it correct to assume that i may have 2 deteriaded
ceramic filters? ( i think they maybe the 10.700 Mhz type) or though i
see 633I on the cases. they are 3 pole type filters. the unit uses two
in series with a load resister in the middle where they are joined
going to ground ..
the first unit i may have aprox 150 mv going in and only about 10 mv
coming out. the secone unit has the 10 mv going in and about 5 mvs
coming out..
this is with a clean signal of course.
i notice the drop is very large ? at least on the first unit, i did
try a 4.5 Mhz cermaic filter i had between a generator and the RF meter
with the center pole to ground and i got the same or if not slighlty
more RF voltage at the reasonant point coming out so i can only assume
that maybe i have something wrong with the units in this receiver.
I did a temp by pass of these filters with a small Disc Cap and i
then got full Scale readings in stations that should be doing so..
after reading all that i just posted does it seem that the ceramic
filters have crapped out over time ?
the owner of this unit did say that i never had a suddent lost of
signal strenght but did notice in the last couple of years of so of use
i thought it wasn't doing so hot on receiving FM stations.

So what do you think ? and how can i tell the exact resonant
frequency with the numbers 633I stampt on it.?
thanks..