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MD Scrolling Horizonal Lines After About 1 Hour?

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Hello,

I'm hoping someone can help with an issue I'm experiencing with my Sega Mega Drive VA4 HDG.

Console is connected to a Sony Tinitron CRT via RGB Scart. After playing for around an hour the console begins to show horizontal scrolling lines on certain colours (Greys, Greens etc). I've replaced the two voltage regulators in the console and the capacitor in the power supply but the problem remains.

Any help would be greatly appreciated.
 

s8n

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hi Axel , you may want to try and touch various chips if they get hot after 1 hour of use.
 
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hi Axel , you may want to try and touch various chips if they get hot after 1 hour of use.

Hello, thank you for the suggestion.

I'll give that a try, if a particular chip is getting too hot what could I do about it?
 

s8n

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i'm not an expert but i had some problems with a AES i bought and some guys at another forums said asked me to check for hot chips. I'm guessing that if i did find (which i didn't) a hot chip it means it needs to be replaced as it's on the way out. Others here can verify if that is the case
 
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i'm not an expert but i had some problems with a AES i bought and some guys at another forums said asked me to check for hot chips. I'm guessing that if i did find (which i didn't) a hot chip it means it needs to be replaced as it's on the way out. Others here can verify if that is the case
Ah OK, so its not a case of sticking a heatsink on the top of it :) I'll check for hot chips and report back with my findings.

Thank you very much for the tip, much appreciated.
 

Tokimemofan

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Could be a power issue. Check the capacitors and the voltage regulator. They don’t necessarily need to be bad, just needs to dump enough interference into the analog circuit. Ideally power circuitry shouldn’t be anywhere near AV circuitry but most consoles locate them near each other. Try adding an extra capacitor between the 5v output of the 7805 and ground.
 
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Could be a power issue. Check the capacitors and the voltage regulator. They don’t necessarily need to be bad, just needs to dump enough interference into the analog circuit. Ideally power circuitry shouldn’t be anywhere near AV circuitry but most consoles locate them near each other. Try adding an extra capacitor between the 5v output of the 7805 and ground.
I've replaced the regulators but have been hesitant to do the caps as it seems like a mammoth undertaking.

Could I solder the capacitors directly to the legs of the regulators and any idea what rating caps I would need?

Thank you very much for the help.
 
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I played until the problem presented itself and removed the cover, none of the chips felt particularly hot. The only heat was from the heatsink on the Voltage Regulators which was VERY hot.
 

Awbacon

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No surprise the voltage regulator chip was got, but might still be an issue?

I’d recap the board. First things first normally when problems develop over “powered on” time, it points to capacitors that are on their way out.

I’d be surprised if a cap kit didn’t solve the issue.

Turbo Duos and PC Engine rev 1 Duos are famous for this. System has audio, play a bit, audio gets quieter and quieter. New caps solve it
 
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No surprise the voltage regulator chip was got, but might still be an issue?

I’d recap the board. First things first normally when problems develop over “powered on” time, it points to capacitors that are on their way out.

I’d be surprised if a cap kit didn’t solve the issue.

Turbo Duos and PC Engine rev 1 Duos are famous for this. System has audio, play a bit, audio gets quieter and quieter. New caps solve it

Thanks for the information, I'll order the capacitors tomorrow and go for a full replacement. I just thought capacitors either worked or they didn't so it's good to learn that's not the case.

I'll report back with the outcome in a few days when it's all done.

Thanks again
 

Awbacon

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Thanks for the information, I'll order the capacitors tomorrow and go for a full replacement. I just thought capacitors either worked or they didn't so it's good to learn that's not the case.

I'll report back with the outcome in a few days when it's all done.

Thanks again

Yeah caps are weird and can be out of spec without being 100% flat. Hopefully the cap kit solves it!
 

Ergot

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Well after replacing all the capacitors and extensive testing I'm pleased to say the issue has been fixed :)

In addition the sound clarity has also improved quite considerably which is surprising as I thought it sounded great already.

Thank you very much everyone for the help ?
 

Awbacon

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Well after replacing all the capacitors and extensive testing I'm pleased to say the issue has been fixed :)

In addition the sound clarity has also improved quite considerably which is surprising as I thought it sounded great already.

Thank you very much everyone for the help ?

Awesome. 9/10 times its always the caps. Even if its not, nobody was ever upset about having a fresh cap kit in their console!
 
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