How To Safely Use An Oscilloscope On a Nanao MS9?

[zed7]

Hi everyone, my Nanao MS9-29A is having what I've deemed to be a sync issue.

Here's a video.

I originally thought it could be 60hz interference; however, I now think it is sync as different game boards yield different results.

The Sega Touring Car manual that specifies to scope TP1 for the sync sine waves and measure the peak-to-peak voltages.

I'm worried about doing this, as this chassis is a hot chassis and does not utilize and isolation transformer or earth ground. I believe I can hook the scope up to the on board heat sink, but NOT the frame as it should be live. I do not want to damage anything, so I am wondering if anyone has had experience with the MS9 and scoping it here.

The LA7853 is a little expensive to just replace it on a hunch, which is why I'd really rather scope the circuit first.

Thank you!

[mikejmoffitt]

This isn't a "hot chassis"; the only hot part is the primary side, over to the left. After that yellow transformer near that, everything important is on on the secondary side. That yellow transformer provides the isolation you want.

The MS8-29 however is a huge flaming turd and doesn't isolate anything but the RGB path so do be wary of it.

Check if your chassis has the two blue disc capacitors underneath the large power resistor. The MS9-29A should have them.