Rebuilding my old analog console

[Kevint]

Hello everyone

My name is Kevin. Back in the early 80's an old friend of mine was an electronic wiz and built a pretty elaborate analog laser light show console (some of you may even know him). He shared some of his schematics with me and I built a scaled-down simple version of it. That was 35+ years ago. I decided to take the parts that I had and rebuild the system. In a nut shell it consists of 4ea Burr Brown 4423 quadrature oscillators with a 3 position selector switch for selecting 3 different frequency ranges based on the value of 3 capacitors and a potentiometer to change the frequency range. The sine and cosine outputs go through a potentiometer to control the gain and then feed a switch matrix that connects to the summing amp. The switch matrix take each sine and cosine signal and feeds each of the 4 LM741 summing amps. This is how all the signal mixing was done. From there each of the 4 signals go into a power amp section. This consists of another LM741 op amp and a TIP41 and TIP42 transistor. There are 4 power amps to drive each of the 4 g120 x-y galvos (2 pairs). Sorry for the long description thats just how my brain works. I have the 4 oscillators, 2 summing amps and 2 power amps sections breadboared and working (for the most part). It drawing pretty nice patterns.

I am by no means an electronics person. I can tinker and get thing to work but not much more then that.

I would really like to add on some additional capabilities/controls like image rotation and such. In my friends system he had 4 VCAs after the summing amp and then some type of image rotation that used 4ea of XR2206 or XR2208 chips (I can't remember which chip it was - I'm getting old). Forgot - I also have a +/-15vdc offset signal feeding the op amps. Its uses a joystick the moves the image around

I'm doing this for fun and to share with my grandkids. If there is anyone here that can point in a direction for a schematic for VCAs or Image rotation that would be awesome. I would love to be able to add this functionality.

Thank you,

[laserist]

You might want to check out the CYGN-B, CYGN-A, and Old fart's comments, experiences and insights there's a lot of info interspace with commentary...

[Kevint]

Thank you for that. I think I'll draw up a circuit schematic of what I have so far and post it over there. You are right there is a lot of info but not sure I can decipher it, but I'll give it a shot.

[mixedgas]

Here is a link to a rotator:

https://photonlexicon.com/forums/sho...=image+rotator

as long as you buy the old CMOS chips, not the modern HCT, your good.

XR2208 are long gone, and extremely fragile.

You might consider picking up an FB4 and Beyond, from Pangolin, then use the FB4s graphics input and go from there.
The Rotator abstract console from Neon Captain / X-lasers can do similar things.

Steve

[Kevint]

Steve, thank you so much for that. That looks like something I could build but I'm not sure how to input the rotation signals in the middle of the schematic. Do you know if there is a schematic for that section?

Here is what I have so far. It works but does have some issues. I still have some wierd voltage offsets occur when i adjust my gain pots and my circles aren't really round at higher frequencies and will collapse to a diagonal line.

Here is a picture of my breadboared.

[Kevint]

I also tried to attach a couple of videos but its not letting me upload mp4 files. I'll see if I can find something that works.

[Kevint]

Here are a couple of video's

[mixedgas]

It's known to work. The digital section simply is a digital word for the angle, or the output of a counter chip. I need to build a new digital section, PC parallel ports are a thing of the past. Probably will use an AVR Processor in the form of a arduino such as a Uno or Pico board.

I ordered the correct analog switch chips today. Stay tuned

As for your console.

The 4423 chip can be a bit squirrelly at high frequencies. There are ways around that like changing the capacitors to lower ESR parts. Also building it on a breadboard tends to lead to stray capacitance problems, something the 4423 hates with a passion.

lm741 was OK, but Tl082 or Tl084 is better.

Steve

[Greg]

I would really like to add on some additional capabilities/controls like image rotation and such. In my friends system he had 4 VCAs after the summing amp and then some type of image rotation that used 4ea of XR2206 or XR2208 chips (I can't remember which chip it was - I'm getting old). Forgot - I also have a +/-15vdc offset signal feeding the op amps. Its uses a joystick the moves the image around

I'm doing this for fun and to share with my grandkids. If there is anyone here that can point in a direction for a schematic for VCAs or Image rotation that would be awesome. I would love to be able to add this functionality.

The AD633 rotation circuit was given on this page: https://photonlexicon.com/forums/sho...8-CYGN-A/page6
and has the added advantage of being hand drawn on a Zeiss letterhead notepad.

How old are the kids you expect to introduce the joys of analog image synthesis to? Have they seen your cycloids? What were their reactions? I work in early learning, and have been considering how I would configure an analog panel young children could successfully explore, and, more difficult to figure out, what output device could survive and be safe in an early learning environment.

[Kevint]

Thanks Steve I'll have a better reply is a few days. Just had my first experience with vertigo - so my head is not there yet. Got some meds from the doctor.