On 24 Feb 2004 22:31:35 -0800, (Bill Meara) wrote:

I have an old Heath SG-6 signal generator. It uses two triodes.
I'd like to convert it to solid state. The switched coils, varible cap
and dial mechanism are very nice. Any suggestions on what kind of
oscillator circuit I should use? I imagine the difficult part will
be coming up with a feedback circuit that will cover the 160 kHz to 50 Mhz.
Any ideas? Has anyone seen any articles on this kind of conversion?
By going solid state and adding a few buffer stages I'm hoping I could make
this thing a lot more stable.

A couple of decades ago (****e, time flies) I purchased a Marconi TF995A/5 sig
gen. In common with many gens of that era, these suffered warm-up drift and the
occasional wander after that.

Well, this one didn't. I'm not saying it didn't drift, but nothing like its
peers, and it warmed up quicker. Explanation? The previous owner had fed all
the fils off a regulated 5V DC add-on. Might be worth a quick try to see if
that approach gives you enough improvement, before you get into serious
redesign.