Interference & Very Weak Colour on MB3514 Video Encoder

Hewitson

Hewitson

Metal Slug Mechanic
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I'm trying to mod my Megadrive 2 in order to get colour in 60hz mode via composite. Its working, but theres quite a lot of interference on the screen and the colours are very weak.

The only modification I have made to the system (apart from putting it into 60hz) is cutting the subcarrier input pin from the MB3514 and connecting it to a PAL frequency crystal oscillator via a .1uF coupling capacitor.
 
Hewitson

Hewitson

Metal Slug Mechanic
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RGB is very uncommon on TV's here. The TV in the lounge does not have it, which is why I did the mod.
 
Hewitson

Hewitson

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When cutting the trace for the colour subcarrier frequency input to the encoder I firstly cut the wrong one which led to a bank of SMD resistors. I'd forgotten about this, when I patched it up the problems disappeared.
 
Hewitson

Hewitson

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Well I now have a new problem with this mod, just got an AV cable (was using the RF unit) and with the AV cable the colours flash brighter on & off intermittently (mainly blue for some reason).

Apart from taking the RF unit apart and seeing what resistors/capacitors it has in it that may stop this from happening when using it, does anyone have any ideas?

Cheers
 
channelmaniac

channelmaniac

Mr Neo Fix-it
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Bad solder joint?

Intermittent short or component?

Easiest way to track that down is to use an oscilloscope to see where the bouncing blue is originating.
 
Hewitson

Hewitson

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Its nothing like that as it works perfectly through the RF. Both the AV and the RF cables connect to the same composite video pin on the AV connector on the back of the machine.

So there must be something in that RF unit that eliminates the problem. I just wish I knew what it was as it can't be opened without breaking it :(
 
channelmaniac

channelmaniac

Mr Neo Fix-it
15 Year Member
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You either have a problem with the output of the system, the cables, or the input on the TV. That's why I suggested an oscilloscope as that will help you track down where the problems are!
 
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