Rebuilding my old analog console

[Greg]

* Is AM in some type of AM modulated signal or the CV control voltage like a sinewave?
* Not sure what the sweep signal in is or where it come from.
* What type of signal feeds the X or Y input?
* Where does the sweep out signal go?
* Not sure where the AM offset output signal would go.

X and Y are +-10V signals from your cycloid generator of choice. AM, usually a ramp, is a +-10V control voltage signal that in this case goes to the AD633 four quadrant multipliers. Inverting the AM signal to either the X axis or the Y axis results in the "diamond" effect. I looked at your video and yes, that is obviously what you are already doing. Sweep is the the AM signal summed with one axis. In the circuit I posted, it is better to take the AM signal before it is summed with the DC offset voltage. The direction effect simply selects X or Y axis to apply the sweep to.

A caution: According to my notes, the circuits I posted are what I built, which works great. I think my original notes are correct, but I'm not guaranteeing it.

[lasermaster1977]

I can hear Aurora saying "Look... The ships!"

Schematic for inverted, diamond, sweep, and direction effects:

Greg, just curious, is the DC Offset pot value also 10K like the AM and Sweep Gain pots, to ensure light loading by the op amp's 100K input resistors?

[Greg]

Greg, just curious, is the DC Offset pot value also 10K like the AM and Sweep Gain pots, to ensure light loading by the op amp's 100K input resistors?

Oh sorry. Yes, it is 10K. I'm inclined to pull the board and inspect to confirm the circuit matches, as something doesn't seem right about how the offset voltage happens after the invert. But maybe I'm second guessing myself. I'll check it as time permits.

[laserist]

Laserium's spiral ramp was a 0-10V signal. While you could use a +-10V ramp with 4 quadrant multipliers the image would invert in both axes as the ramp went negative. It would be an interesting look, but inverting a +-10V ramp wouldn't lead to diamond spirals...

[Kevint]

Just a guess on where to look (if this is the KQO circuit) :
Bad op amp or its PSU/Gnd connection(s)
Bad 15v power supply connection(s)

reply edited since 1st post

I just took another look at your scope photos and now noticed that in the first photo the Ch1 and Ch2 signals are at the same frequency, but in the 2nd photo one is slightly higher that the other...they should stay the same. Attention should now be paid to the capacitors (one is leaky? and/or changing with time?) or their RC/op amp connections are not solid?

Nice find in the scope images. Ok that sounds good. Let me play with the caps and op amps and see what turns up. Thank you.

[Kevint]

X and Y are +-10V signals from your cycloid generator of choice. AM, usually a ramp, is a +-10V control voltage signal that in this case goes to the AD633 four quadrant multipliers. Inverting the AM signal to either the X axis or the Y axis results in the "diamond" effect. I looked at your video and yes, that is obviously what you are already doing. Sweep is the the AM signal summed with one axis. In the circuit I posted, it is better to take the AM signal before it is summed with the DC offset voltage. The direction effect simply selects X or Y axis to apply the sweep to.

A caution: According to my notes, the circuits I posted are what I built, which works great. I think my original notes are correct, but I'm not guaranteeing it.

The diamond spiral I created was just a guess after reading your post earlier. My function generator has 2 outputs so I created that pattern. I still have the build the boards that DZ provided to get a good AM signal source instead of using the function generator.

Thanks for the info on the circuit - that will get me started and I'll attempt a build this week.

[Kevint]

Laserium's spiral ramp was a 0-10V signal. While you could use a +-10V ramp with 4 quadrant multipliers the image would invert in both axes as the ramp went negative. It would be an interesting look, but inverting a +-10V ramp wouldn't lead to diamond spirals...

Interesting. Since I used a seperate +- ramp for my AM signal I have something that is similar to but not diamond spirals. Thank you.