WANTED: Good Source of Electronics Theory

I am a home hobbyist who enjoys restoring vintage stereo equipment.  I
have a good working knowledge of electronic components and what they
do.  I have decent test equipment and good soldering skills, and most
of the time I am able to track down and repair a particular problem.

However, I do feel that I need to know more about the theory behind
electronic circuits in order to improve my troubleshooting skills.

Sometimes I find myself looking at a schematic and thinking, "Boy, I
wish I knew more about what is supposed to be happening in this
circuit!"

Can anyone point to any good books or online sources where I can learn
more about how to analyze schematics and recognize what is supposed to
be happening?

CASE IN POINT: I am attempting to repair a tape deck.  One channel
(the right channel) of the headphone amplifier doesn't work.  The tape
deck has perfect output through the line out jacks.

Here is the schematic for one of the channels of the tape deck's
headphone amp:

http://i240.photobucket.com/albums/ff58/eadgbe123/amplifier.jpg

I have reproduced the schematic in my own handwriting because the
downloaded schematic was too fuzzy to scan.  I *think* I have copied
everything correctly.

I cannot figure out why this particular circuit isn't working
correctly.  I have checked each component--and even replaced a few
transistors even though all transistors tested fine--but nothing is
improving.

I have tested all of the electrolytics with my ESR meter and they all
check out OK.

I have checked all resistors and none of them have opened up or "gone
high".

Notice that there are some "typical" expected voltages indicated at
certain points.  These "typical" voltages have come right out of the
service manual.  All of the voltages marked "OK" are...well...OKAY.
But the three voltages marked with a star (*) are NOT okay...they are
all just a few millivolts each--around 20 to 30mV.

All capacitors are electrolytic with the exception of the 4.7pF
capacitor, which is ceramic.

All resistors are 1/4 watt.  If there is no "K" after the number, then
that is the amount of actual ohms it has.

For the record, I replaced Q204, Q206, and Q208 but still got exactly
the same results.

What am I overlooking?