Master System 2 Video Interference After RGB Mod

[Trevor spencer]

Hi

I decided to RGB and 60hz mod a master system 2 I had lying about with a PCE RGB amp i had spare and it worked only problem is sometimes on lucky dime capers I notice some strange dots at the top of the picture while running in 60hz mode but i get perfect sound.
This dosnt happen on alex kidd on that game i get a perfect picture but I get audio hum.

Are these systems just crap or is there something I could do to try and fix this. I remember I had a similar problem with noise at the top of the screen when I 50/60hz modded my MD2.

Thanks

https://ibb.co/h9Msgds

https://ibb.co/2FND7bN

[skum]

I've modded several SMS2's to RGB and 60Hz, always with really good results, but I never installed a new RGB amp, so I guess you're bypassing the CXA1145/MB3514? In that case I guess your wiring should be looked at. Can you show more of the complete mod?

[Trevor spencer]

Hi i basically followed this guide but instead of making the vero board up i installed the PCE RGB amp , to be honest i wasnt sure if it was going to work but thought id give it a try

http://www.mmmonkey.co.uk/console/sega/sms2-av.htm

Ive also got the 5v and GND piggy backing off of the amp to the DIN socket.

Thanks

[rama]

I'd say this is a pretty good picture from that system.
The dots are probably of the same origin as the better known Mega Drive VDP dots.
The MS used an earlier design of that chip, I think.
https://i.stack.imgur.com/YBKCl.png

Audio hum is usually indicating an insufficiently shielded cable.

[Trevor spencer]

Hi

Thanks for the reply , so you think this could be normal ? like i said there is no effect like this on the inbuilt alex kidd game.

I've ordered a cheap game off ebay to try also so ill see what that is like , its a shame as apart from that it looks really good.

[rama]

As on Mega Drive, it depends on the programming.
The dots could be avoided if the programmers were careful.

[Trevor spencer]

Ahh thats good to know , shame as that donald duck game looks really nice.

[rama]

Maybe your TV has some overscan options? Something to "zoom into" the picture.
The dots tended to be hidden in the overscan area on old CRT TVs (though that wasn't intended, it hid them well back then).

[Trevor spencer]

I can get into the service menu and hide the outer ones but i noticed tonight that sometimes they briefly appear in the middle of the picture too, I'll try and take a video.

I've never tried this game in another system so don't know if it's a dodgy cart.

Ive got 2 cheap games coming soon so I'm eager to try those. I've had alex kid running for about an hour tonight and didn't notice any video problems.