Rebuilding my old analog console

[Kevint]

Thanks Ron. The image explains a lot. It make me want to check and see exactly what the clipper circuit is doing on the KQO circuit. At the outout end of that circuit there is an opamp with 2 diodes for each scan axis.

[laserist]

there's a bit of confusion. This is the clipper circuit Ron and I were talking about:



Which is adjustable

and this is what I think? you're talking about



which uses 1N5239's and isn't adjustable, and just squares off the KQO and may have been added for the PD100 feedback scanners.

[Kevint]

Brian, that is a big difference and type of circuit. Thanks for clarifying. With that, I wonder if the clipper circuit in the KQO is causing my drift issue. When I turn the circuit ON the KQO is in the center, as it runs is slowly drift at a 45 degree angle up to 6 inchs from the center with the scanners about 24 inches away. If I turn the power OFF and then ON it recenters and slowly drifts again. When I look at the scope image, the KQO signal has a DC offset when if drifts. I was thinking it could be thermal related so I bought a can of cool spray to see if it helps locate the culprit.

[Greg]

Here it is in Crystal Odyssey clipping a simple 2-oscillator cycloid into UFOs:

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

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

[laserist]

Brian, that is a big difference and type of circuit. Thanks for clarifying. With that, I wonder if the clipper circuit in the KQO is causing my drift issue. When I turn the circuit ON the KQO is in the center, as it runs is slowly drift at a 45 degree angle up to 6 inchs from the center with the scanners about 24 inches away. If I turn the power OFF and then ON it recenters and slowly drifts again. When I look at the scope image, the KQO signal has a DC offset when if drifts. I was thinking it could be thermal related so I bought a can of cool spray to see if it helps locate the culprit.

It sounds like an op-amp is acting like an integrator, but I wouldn't think the image would be close to right in that case...

[Kevint]

Brian: here are the x and y scope traces. One at startup and one after running for 30 minutes. There is a -2Vdc offset coming from somewhere. I'm still investigating.

[Kevint]

Is this image close or have the same concept to what is called a diamond spiral?

It is the KQO with a 12Hz AM modulated sinewave. One axis has a positive offset and the other a negative offset. The signals for the AM are coming from the function generator. I am so glad I bought this thing.

[Kevint]

Greg. Thanks so much for posting the schematic, but I'm not sure how to hook it up or where in the system it would go. Here are a few questions:

* 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 shure where the AM offset output signal would go.

Sorry for being a pain.

[lasermaster1977]

Brian: here are the x and y scope traces. One at startup and one after running for 30 minutes. There is a -2Vdc offset coming from somewhere. I'm still investigating.

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?

[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.