I picked up a Sony PVM 27QM recently. Generally I'm happy - my consoles look fantastic on it over RGB. It has some very minor image issues there that I think I'll be able to fix or live with, but that's not what's bothering me. Whilst it has a SCART socket, it doesn't seem to accept composite over SCART as a video signal (I'm assuming it only uses composite for sync, hence the resulting black screen). When I set my DVR to CVBS, The PVM completely ignores it - it still displays RGB. Mostly this isn't an issue, I don't use composite unless there's no other option... unfortunately, that's the case for the NES. I know I could pick up a Titler for RGB but they're so expensive. Now, it does have some BNC connectors for video which I've put a BNC to phono converter on. When I plug in my NES, though, it looks like this: The colour bars you see remain in place - they aren't rolling, the image doesn't roll at all, there's no white noise interference, just the colours are completely wrong. Doesn't matter what game. I've tried all the composite connections on the TV and they all look the same. I've tried another composite source, one of those shitty Atari-in-a-pad things, and it exhibited exactly the same issue - stable image, strange colour bars. The TV detects both as PAL. Sound works fine, for what it's worth. Any ideas? PVMs are a different breed so there may be something obvious I've missed, though I'm pretty familiar with the face controls and the nobs out back.
While I don't have any suggestions on how to fix it, all I can say is I have a 19" Sony PVM. I also put a BNC to Phono Adapter on mine for Composite Video and my NES and Genesis both work fine on it, no issues like you are having. All I can suggest is to check all the switches you have on your model to see if there is something you can change to fix it. I know on mine there is a switch that forces SECAM instead of using Auto Detect.
Might be a problem with the colour decoder, although check your BNC termination, and make sure it's not set to 75ohm (if this option is available). Have you tried turning the colour (or chroma) control to zero? If there's any remaining colour then there's definitely a fault. Alternatively to get round this easily, you can use a DVD recorder to accept the composite input and output RGB to the PVM. You'll then be able to circumvent the PVM's own Y/C colour decoder circuitry.
Flicking the 75 Ohm switch just makes the image darker. Same colour problems. Buying a DVD recorder seems wasteful as I don't need the DVD player or recorder functionality, and I'd be concerned that presumably at least some DVD recorders just pass through SCART. I've had a poke around and dedicated composite-to-RGB boxes seem very pricey, in the £70 region. Surely Extron or someone made a little box that did this and can be found cheaply?
I've seen second-hand Panasonic DVD recorders on eBay for around £40. Something like the DMR-ES10 would be ideal. You'll be able to watch DVD's and TV on your PVM too! Having had experience with the Panasonic ones, they do have an option to permanently set the A/V output to RGB. It'll then convert anything to RGB.
Thing is, I've already got a DVR and a DVD player set up (and any widescreen content gets seen on my 1080p screen anyway), and these DVD burners are pretty bulky. Also £40 just to patch through an otherwise perfectly working NES seems kind of a rough deal. Cheers for the advice though, it is appreciated. I might look for one with a broken laser unit.
I have Sony PVM 1271Q (13" model). Mine's probably older and in worse shape than the model you have, but it's still fully functional. Anyway, it's been a while since I tried to send a composite signal through it, but every time I did I found that the colors were wrong when I initially plugged it in. The solution: I wiggled the BNC connector in the back around a little, and as I did so the colors changed and flickered until eventually they were right. I had to leave it in just the right spot for the picture to stay correct. This is probably due to a bad connection inside the monitor, but it's something you might want to try before you go spending a lot of money. Just a thought.
I've tried it on all four sockets, and that involved plenty of jostling. I'm going to take the back off soon to adjust the horizontal positioning so I'll check the contacts then. Was it blue/green bands like in the pictures, just out of interest?
I can't really remember because it's been a long time. I don't think there were bands, though - I think the whole image was off-hue. So now that I think about it that was probably something different than what you're talking about.