Mega Drive Model 1 S-Video Noise

Hi guys

I am new here, my first post, maybe you can help me solve the problem I have with my recently modded PAL Mega Drive Console (Model 1).

A week ago, I decided to add Composite Connectors, S-video and 50/60hz switch to my Mega Drive.
I was following DamoMonster instructions, and all went well.

Composite works great, frequency switch works great as well, but S-video is what is giving me headaches.

There are jail-bars which I don't mind that much, but also there are weird "Zipper Lines" going from left to right, and are quite noticeable.

I am trying to figure out whether this additional noise is normal to have, or have I done something wrong?

Console is being used on a Bravia LCD, so not sure if this is a problem too.

Sometimes the screen will disappear completely for a second.

Also, sometime picture will be very distorted and would have "rainbow" color kinda effect going across the screen, a restart usually fixes this. It will definitely always happen when switching to 60hz and vice versa on the fly.


Image of the zipper noise and color distortion attached.

Any assistance would be greatly appreciated.

Thanks

 

Did you use shielded cabling inside and out? Also, check your ground connections soldering. Might be a weak joint.
About s-video jailbars, you can usually mitigate them with a 500 ohm pot on the chroma line.

 

Hi

Thanks for your help.

No, I did not use shielded wire, I used a normal 0.5 mm I pulled out from some old TV.

You think this is the problem? Hmmm, I don't know if I can find a shielded wire that thin, because the wiring is going underneath the motherboard (between the metal shielding plate and mobo).

Do you think an RCA wire could do the trick, it looks shielded, does look cheap though, and not the best of quality...

I have also noticed, that when I bridge pins 5 & 6 on the video chip with my finger (which are cut btw for color fix) the zipper noise dissapears somewhat, but not entirely?


Thanks

 

Shielding your video signals always help.
I cannot say it if will fix your problem but I always use it.

I actually cannibalize cheap RCA cables for single braid shielded cabling.
At a wholesale store nearby they sell those 6' stereo RCA cables for 2.99$.
You can split them in two mono cables and I just cut the connectors off and end up with 12' of shielded single braid wire, it is actually pretty good quality too, shielded with pure copper.

 

Thanks for that.

I found a cable, that might do the trick. Will have to try this out tomorrow.

Do I have to solder the shielding to ground, or will just using the middle/main wire do?

Thanks

 

You got caught up in the anti-spam system for new users, unfortunately. It should get better once you've posted a bit. For now, remember that your post may go to the moderation queue for approval and not show up - there's no need to keep posting it, just wait for a moderator to approve it ;-)

 

Thanks for explaining that retro.

I have completely re-done the mod, using RCA cables, this time I grounded each from the bottom side of the motherboard.

Still the same, noise is present, and it looks like it becomes more apparent as the console heats up. Something is possible wrong.

Quite disappointed I didn't go with the RGB cable in the first place, instead of spending so much time and no results in the end.

Thanks for help

 

What type of transistor did you use for the S-video? Would it be easy for you to try another type of NPN transistor? I use BC337 with success, but I haven't tried it on an lcd screen either. I have a 66cm Sony Wega CRT around for retro duties.

 

Initially I used 2N3904.
When I redid the mod, I used C546B.

I have TIP31 handy, but unsure if something this powerful is needed.

I hot glued everything already, but would not mind pulling apart to have this fixed, if anyone has any ideas what could be wrong?

Oh, and also, the noise is present when I use composite on CRT TV as well, so yea....

Thank you

 

Are you using original power supply or switchmode? Have experienced some horrible stuff with some switchmode power supplies especially in video.

 

Hi

Original 10V, 1.2 A PS.

Maybe the PS is on its way out? Have thought about that, but dont have spare one with same specs. I have Master System on, but its 9V, 1A.

Have tried MS one though, issue remains.

EDIT: Have just tried Mega CD power supply, they are the same. Problem is still there.

Thanks

 

Hi Guys

Just an update, I managed to fix the problem on my Sega by adjusting the variable capacitor.

Not sure if I should make a separate thread for this, but will post here first.

I have the same noise on my SNES console, and the only mod I have done on it is 60hz mod.

The noise is only present when switched to 60hz mode? I should also mention, that I am using composite cables.

I have no idea what could be wrong here.

Has someone experienced the same issue?