@laserist This should bring back some memories.
Mark 4 Patent
http://patft.uspto.gov/netacgi/nph-P...S=PN/4,006,970
I outed that patent on the old laserist list about a decade ago. I've got 2 - Mark 6B's and a Mark 600 (a Mark 4 optical head and what evolved into the Mark 6 console) here in St. Louis for my reboot experiment. (and to bring them all up to performance standard…) I've been flying down memory road…
Laserium's analog quadrature osc used 2 OpAmps for the sin/cos and a third for inv sin, but the inv sin signal was inserted into the sin/cos feedback loop for fine freq control if I recall...
"There are painters who transform the sun into a yellow spot, but there are others who, with the help of their art and their intelligence, transform a yellow spot into the sun." Pablo Picasso
Did someone say quadrature oscillator?
Like this?
As is outputs sine waves of pretty good quality. Frequency range is not bad, you can switch the capacitors to make different frequency ranges. Since it's a voltage controlled oscillator you can do frequency modulation pretty easy (sum/switch in a signal where the potentiometer sits. Easy to make the sine into a square wave with another op-amp at high gain. You can turn that into a triangle wave with a little more work.
3280s aren't impossible to find. Sure ain't $90, or you aren't looking hard enough. I made a 'lifetime buy' a few years ago.
I have the L. micheal blackbook circuits if someone really wants them. I think I got the last one. http://www.galco.com/buy/Burr-Brown/4423