Jumpy Mitsubishi 37”

[TronicG]

A while back I shared here how I found a very rare for Euro standards 4:3 37” consumer Mitsubishi CRT. It had H hold issues but some caps and resistors later I finally managed to get it working. But there are still pending issues. Picture is just a tiny bit jumpy all of the time except for very bright scenes where it is very jumpy. Here’s a demo vid: https://youtube.com/shorts/flEwvnJQJ-A ... m3ttMXhwDQ

Any ideas?

[Josh128]

Just a wild guess, but try attenuating the sync signal. This reminds me of the Hitachi MM20/30B dual scan sets. When fed S-Video, they have a great picture but bright flashes cause them to lose sync, every single one of them. Come to think of it, my old 36" Hitachi used to do the same thing with component in as well.

It appears to be something to do with higher signal levels and/or the sets inability to take them, thats the only thing that changes when you do bright or full white scenes. If attenuating the sync signal doesnt work, you could try attenuating the RGB inputs and turn up the set brightness to compensate. On the flip side, maybe your sync signal isnt hot enough.

[Syntax]

Does the set suffer from bloom (increased image size) in the bright scenes also?

[Josh128]

Does the set suffer from bloom (increased image size) in the bright scenes also?

From the video, it looks like the image shrinks horizontally with bright screens. What would you suspect the culprits to be when blooming (growing), or breathing (shrinking). Voltage regulator / power supply issues?

[Syntax]

Yes, if the source has been ruled out as the culprit id be looking at the power circuits and their caps if not already replaced.
I'd missed the video, that is a fairly large change in size. It can also be from a poorly designed powerboard for the cheaper consumer sets.

[Josh128]

Does the set suffer from bloom (increased image size) in the bright scenes also?

From the video, it looks like the image shrinks horizontally with bright screens. What would you suspect the culprits to be when blooming (growing), or breathing (shrinking). Voltage regulator / power supply issues?

[viletim]

TronicG,
How is it possible demonstrate 'jumpy' video with a full screen colour raster that overscans?

[Josh128]

Tim, poor examples agreed, but look at the full white screen-- it is not horizontally overscanned, and you can see the distortion on the right side.

On a side note, do you have any possible idea what could cause a NESRGB to start to lose sync on dark scenes, such as black screen with a little bit of text on it? My launch window unit is now doing this, for a while now. When it begins to lose sync, the black portions of the screen actually turn from black to a gray, and the entire screen starts to distort a bit and shake. When more color or brighter scenes happen, the grey immediately turns back to black and everything lines back to a great looking image.

Something to do with signal levels, but almost opposite of the issue here. It is not the TV (Sony 36" SD WEGA CRT), its definitely the NES/NES RGB. Any brief tips on what I should look into?

[viletim]

On a side note, do you have any possible idea what could cause a NESRGB to start to lose sync on dark scenes, such as black screen with a little bit of text on it? My launch window unit is now doing this, for a while now. When it begins to lose sync, the black portions of the screen actually turn from black to a gray, and the entire screen starts to distort a bit and shake. When more color or brighter scenes happen, the grey immediately turns back to black and everything lines back to a great looking image.

Something to do with signal levels, but almost opposite of the issue here. It is not the TV (Sony 36" SD WEGA CRT), its definitely the NES/NES RGB. Any brief tips on what I should look into?

If this is version 1.0 (it just has NESRGB printed on the silkscreen without a number) then there is a mod to improve the sync separator performance. You need to cut the trace highlighted below and install a 39k resistor between the two points in its place.

[Josh128]

Fantastic Tim, thank you so much, I will give that a try!