Thank you so much for the response! My basement flooded after the big storms here Wednesday and it took me a few days to get back to troubleshooting this issue.
I disconnected everything from my power supply except the Visual Cortex. I monitored the 12V -12V and 5V rails from the power supply while playing with knobs on the VC, and the rails were all correct and steady. I also checked all the grounds and they too were all at 0V. Has anyone else encountered difficulty with Synthrotek power supplies and LZX gear? I don’t have an alternative power supply to check the VC with but I might be able to do so later this week.
That said, I think I may have identified the issue. I set the scale of the scope to look at individual lines and then offset the inputs from the VC and my Kramer Test Signal Generator set to black burst so that the 0 IRE positions were about even. I then used the VC knobs to try to replicate the way the signal looked from the signal generator. The expected behavior, I believe, is that with the knobs at 12 o’clock, I should get a signal that looks like the one from the test generator. Instead, it looked like this:
VC in Yellow, Black Burst from Signal Generator in Blue, scales identical, y-axis offset so 0 IRE levels match:
I noticed that the sync level from the VC as well as the color burst seemed to be at about double the amplitude of that from the signal generator. I then tried comparing a white fade from my Roland P-10 to the VC with the knobs turned all the way to the maximum, which produced the following:
VC in Yellow, White Fade from P-10 in Blue, scales identical, y-axis offset so 0 IRE levels match:
Again, the levels match but the sync and colorburst seem to have double the amplitude. I then tried again with the VC knobs turned to their minimum, which produces no visible video signal:
That seems to be about -0.714 V below 0 IRE, that is -100 IRE, which makes sense if the purpose of turning the knobs in that direction is to remove color from a video signal that is being mixed. From this I can conclude that the range the knobs is covering seems correct, but the “center point” seems off.
Based on this, I tried adjusting the black level using the trim pot on the back of the VC. This had no effect on the 0 IRE level or the amplitudes of anything. While looking at the back of the VC I noticed a number of what I presume are test points for checking voltages. I decided I might as well check those out, so with the VC secured and powered, I checked each test point using a multimeter. They all matched the voltage silk screened on the PCB until I checked the -2 V spot pictured below. That location read as -1 V compared against multiple ground points. Could this voltage being off induce the output errors / odd waveform behavior I’m seeing? Is there any way this could be a DIY fix or do I have to send my VC in for repair?