On Sat, 1 Dec 2007 06:30:26 -0800 (PST), EADGBE
wrote:

(Please forgive me if I say anything dumb in this post...I am a home
enthusiast who is experienced at working on amplifiers, tape decks,
and turntables, but I haven't really worked on tuners at all.....)

As you all may recall, my Technics SA-400 receiver's "FM Stereo"
indicator would not light up, even when receiving any of the strong FM
stations in my area.

A few folks kindly told me how to adjust the VCO circuit. I used my
frequency counter and hooked it up via a 100k resistor to the
appropriate test point and was able to adjust the VCO perfectly to
19kHz.

For a few weeks, the receiver worked great. I was able to get "FM
Stereo" indicator to light AND could plainly hear the stereo image of
my favorite FM station.

But now, the same problem has happened again. The "FM Stereo"
indicator does not light and I do NOT hear stereo.

I was able to verify that the "FM Stereo" light DOES work.
Interestingly, the last time the "FM Stereo" light worked, I was
dialing in a station, the light came on for half a second, then went
out.

It's as if the receiver is TRYING to give me FM stereo, but for some
reason cannot.

QUESTION: What procedure(s) do I need to do to align the FM tuner so
this problem won't happen again? I have a frequency counter, a signal
generator (20Hz to 20kHz), and a Nakamichi T-100 audio analyzer. My
scope, unfortunately, is non-functional at the moment.

Many thanks in advance........


I can't remember if this particular model uses a polystyrene 470 or
1000 pf capacitor in the mpx circuit. If it does, I'd replace it with
a polystyrene or silver mica capacitor and readjust the vco. Chuck