*********** BIG SNIP
Yes, i figured that the design was different even tho the function
seemed to be the same.
Been awhile since i looked at the incomplete Agilent schematic, but the
diode array and biasing should be the same.
In this schematic, except for Q306 and Q309, all transistors are fully
active (no reversed biased E-B or forward biased B-C junctions).
Maybe i should look at their crummy schematic..
..still looking at it; will respond later.
See Agilent PDF page 71 TP5 is equivalent to junction on mine
described by CR322, CR321, R353, R351 and R350. Likewise, TP7 is
equivalent to junction on mine described by CR323, CR319, R352, R346 and
R344.
Lastly, the "center", (sinewave) of TP6 is my TP13.
Now on mine, it is mostly obvious that the incoming triangle wave via
R369 (from output of op amp U301) is/must be symmetrical about ground
and (going from left to right) each pair of diodes will "clip" that
waveform at a level set by their common resistor at the output line
TP13; each clipping point being more severe (lower common R value) and
at a higher level (further away from ground).
Finally, the peak is clipped at the top, set by R348 and R342.
On the Agilent, PDF page 18, note there is NO "high frequency" monkey
business WRT the sine forming, as i seem to have seen mentioned. Ditto
with mine. Exception may be small trim caps or such.
TP6 appears to be at ground with the waveform symmetrical, just like
mine.
So...at "low" frequencies (10-1000 cps) the triangle coming from the
triangle amp (Pg 18 again) better the hell be EXACTLY symmetrical and
well behaved.
And it should stay that way all the way to the high end on the top range.
I think that may be the key, and so there may be more than one
problem - the first being this triangle waveform ain't not nowhere near
symmetrical (to use bad Engrish).
TP5 should be as negative as TP7 is positive; i derived that from the
necessary biasing for that DFG, and the schematic voltages noted confirm
that.
Resistor and voltage values from one to the other in the DFG will be
different, but more-or-less on a ratio basis, they should track.
Once you get the triangle symmetrical, then it should be fairly easy
to find a bad resistor or diode in the DFG (am guessing this as being a
secondary problem).
Maybe one of the stared capacitors in the sine shaper amplifier is
bad, but i doubt it; if there is a problem there HF-wise, it would be
due to a transistor (Q2 or Q3).