Prismatic Ray - Rear panel RCA V-sync twitchy

When we first started using our 2018+ Prismatic Rays (RCA sync), we did not use the rear sync connections. Every patch relied on sync via the front panel inputs, and worked like a charm – all ranges had beautifully stable images. A few weeks later, we chained the rear panel RCA sync connection from the Visual Cortex out, through the Liquid TV, through two Prismatic Rays, and out to the Vessel case connector (with nothing plugged in outside the case). Range 1, 2, and 4 still work well, just like before.

Unfortunately, from that moment forward, both of our Prismatic Rays have displayed some instability in Range 3 with Vertical sync, producing a vertically pulsating displacement in our horizontal bars, spanning about 1-4 scanlines when observed with high gain. With patience and the Fine Freq. knob, a stable spot can be found – but any adjustment to frequency requires that same return to the Fine control.

Even when the PR rear panel sync is overridden with front panel Vertical Sync directly from the Cortex front panel, the twitchiness is still there. I just verified that removing the Vessel case output and/or Liquid TV from the sync daisy-chain makes no difference. And with the rear sync disconnected from the Visual Cortex, the front panel Cortex->PR sync still produces a stable V-sync, as it did initially.

The vertical displacement is most noticeable on our CRT display, similarly noticeable in the Liquid TV, and less noticeable in the Intensity Shuttle’s capture.

What’s the best way to go forward troubleshooting and solving this issue?

Thanks for your time!

Change the Gate/Trigger switch to Gate mode. It’s best to use the Trigger mode only when sync’ing from something like a video camera or other source, as it shortens the pulse width of the sync reset.

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Perfect, thanks @creatorlars!

Bumping this thread because I have a similar issue. Following @creatorlars’ advice I switched to gate mode. This makes the front panel sync look absolutely perfect, but my rear RCA sync is still a bit jumpy. A lot better than before, but not nearly as stable as the front panel sync. Any ideas? I have two Prismatic Rays this is happening with

This is an open issue we’re investigating in the lab, so we’ll have some sort of resolution soon.

Update: I found out that my PR’s don’t stutter when they’re not connected to each other via sync. I only randomly discovered this because I removed one from my main case and then they both functioned as expected. Gotta do some more testing but I’m going to rethink my sync chain and see if I can eliminate the jitter.