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Apr 24, 2023
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Chippenham, UK
I rewired my cab today with a new JAMMA loom which has fixed issues I was having with RGB but created an ominous crackling from the anode cap which also manifests as light speckles on the screen. The JAMMA loom itself has been tested before without this issue, but since then I've spliced it onto a replacement AMP-UP connector from Videotronics, as the old one had been damaged. I've checked and double-checked all the pinouts but am wondering if the problem is where I've spliced the two AC cables for the AMP-UP. I doubt it's the anode cap itself as it looks very clean and didn't have this problem before splicing the new loom.

The bridge loop on the left is the degauss pins, which is how the AMP-UP in my cab was previously, and which didn't cause issue with the old loom.


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Everything checks out. I don't have a V-sync pin wired up as it's not on the MS9 pinout. The two AC pins (6 and 7) are bridged (at the isolation transformer as well) but I'm guessing that's how they should be?

Was repeating the degauss wiring from my old Sanwa chassis a mistake? Should I have it connected to a switch instead? Presumably this loop means the circuit is always connected, which sounds... iffy.
I cut the degauss loop and tried connecting a spare Pandora's Box instead of my usual RGB-Pi Jamma, and touch wood the problem's gone away.
So, the problem has returned. I haven't been leaving the cab on long enough to know if it gets worse over time - I'd rather not find out! - but I guess the next step is to clean around the anode cap and get some dielectric grease in there. No visible sign of where the occasional 'crack' comes from, just the odd speckle on screen.

Is it at all possible this is something to do with the wiring of the cab, or is it more likely to be an issue specific to the monitor?
What monitor is this? This sounds like my MS-2931 before the flyback went bad.
It's an MS9-29. Good news is that I cleaned up around the anode and the cup itself with some isopropyl, then put dielectric silicone grease around the inside rim of the cup. Problem has once again gone away.
So, it was the anode all along? Interesting. I have seen this behavior with grounding that, once removed, would fix the issue.