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wrote:

snip
My experience with several dozen HP 200's does not match yours.
Yes, they all oscillate, but amplitude stability and phase noise is
tube dependent.

i have probably just been lucky. Also I pay little attention to the
dial markings, I use my freq counter to set frequency. And I don't use
them for scope cal, there are precision level gens that are used for
that.

The tube-bigot lie here is that most ICs in good audio test equipment are
standard parts, or can be readily replaced with standard parts.

IIRC the 8903 has a proprietary diff amp that is close to unobtanium.

If you recall, the 8903 is a fairly rare beast in and of itself

Oh no! They were sold by the truckload because they replaced the 339.
Then they went to *ucker in trade for....used 339s....because they
weren't. Potomac IIRC essentially cloned the 339, but in two boxes, a
gen and receive, and charged more for either than HP had for the 339.
So 8903s are common as sin. However, barring abuse, they run forever.

and
hardly
constitutes an example supporting your claim. I have an entire wall
of audio test equipment from HP, ST, Techron, GR, B&K, Leader,
and so on, and there's nary a proprietary IC in any one of them.

Now the exception is my old, trusty GR 1390B random noise
generator which uses a proprietary noise diode. if it goes, the
unit is worthless. WAIT! It's a vacuum tube, not an IC! Fancy that,
a proprietary, non-replaceable vacuum tube.

HP solid state RF gens use a lot of proprietary silicon-8640s

Lessee, HP 8640: signal generator with a range of 500 kHz to
500 MHz. Please explain how that is "audio test equipment."

Well, then I guess an FM tuner isn't an "audio unit".