RGB Horizontal (left shift) correction circuit and layout

[MEGADRIVE Jeroi]

I have found horizontal fix circuit from nffgames forum and building layout circuit to get etching board.

I have given this circuit a new short name: HCF which stands Horisontal Centering Fix

If you are interested to test the circuit on your own here is the circuit for you:

shiftysync.jpg

I am adding later my circuit layout and Eagle chematics and libraries for NE558 chip to this thread.

I am modding my layout to fix into 2 way active scart divider and hoping to add switch that makes the divider go poweroff-normal-horizontalfix states. When switch is on horizontalfix -state I can then rotate the 10k potentiometer to get my image sifted to right. So i get power from scart divider, and comboshit signal from scart input. then I add the horizontal and normal modes via 3 state switch.

Here is photo of my current fitting testing with paper:

layout_fitting (Copy).jpg

Here are current layout photos of my work:

layout_v1.jpg layout_v1_final.jpg

More images later.

[Drakon]

gamesx....the same place where the wiki has a nes rgb amp with a "low pass filter to remove jailbars" that simply blurs the picture until the jailbars blur away... I'm interested in seeing the results!

[TmEE]

That mod is done by a very knowledgable person. It is definitely good stuff, and will be part of my digitally controlled SCART switchbox once I build it.

[Drakon]

oh okay so it's one of the good ones from gamesx

[MEGADRIVE Jeroi]

Well this circuit is from villetim website not from gamesx website. So it could work very good. I am at the moment figuring how to but my CCAM and HCF layout in same print and print multiple the layouts if somebody here want's to buy some pre made boards for their modding.

[omp]

That viletim is nothing short a fuckin genius! He helped me do the safe language switch on the sms2 so that wb3 works with his fm board. The only issue we had was that the extra mod he said to do to his fm board to get wb3 to work actually had to be undone lol! Also he has a game gear to tv out board rgb, s-video & composhit. Good stuff (and a fellow aussie).

[Drakon]

Yeah viletim makes great stuff. No idea what HCF is but I'm sure it's awesome.

[MEGADRIVE Jeroi]

HCF is Horizontal Centering Fix

[Drakon]

Is that an issue that happens on new flatscreens?

[Chilly Willy]

Is that an issue that happens on new flatscreens?

I think it's more an issue for OLD TVs that didn't have service mode, so you couldn't adjust things like the horizontal position. Any reasonably new TV will have a service mode that lets you adjust everything from the position and size to the color balance.

[Drakon]

I've never had a tv be off horizontally. Is it something you get on rgb tvs?

[TmEE]

Sync is delayed compared to RGB signal, because conversion to composhit takes time, so your image is centered for composhit, but a bit shifted to left in RGB on many TVs.

[Drakon]

Sync is delayed compared to RGB signal, because conversion to composhit takes time, so your image is centered for composhit, but a bit shifted to left in RGB on many TVs.

So I'm going to take a "wild stab" and guess that feeding composite sync into your rgb tv would fix this issue....getting rid of the need to build a big pointless hcf circuit. If you're using a console that has rgb then it'll have composite sync somewhere, even if composite sync isn't wired into the av port you'll be able to tap it from somewhere on the pcb. Feeding your tv composite sync would bypass the entire conversion process....or are some rgb tvs going to convert the signal even if it's composite sync still having the same delay time?

[MEGADRIVE Jeroi]

So I'm going to take a "wild stab" and guess that feeding composite sync into your rgb tv would fix this issue....getting rid of the need to build a big pointless hcf circuit. If you're using a console that has rgb then it'll have composite sync somewhere, even if composite sync isn't wired into the av port you'll be able to tap it from somewhere on the pcb. Feeding your tv composite sync would bypass the entire conversion process....or are some rgb tvs going to convert the signal even if it's composite sync still having the same delay time?

You don't have a glue? RGB uses as sync combosite sync. Because all the consoles encodes comboshit and it takes time, the sync has offset about 15angle and it causes RGB image to sift couple centimeters to left. What is needed is to delay RGB on TV but if not possible then delay composhit even more to get the sync signal exact same angle again.

[MEGADRIVE Jeroi]

I did by pass sync input from CXA to composite output of megadrive. This fixed vertical problems with my lcd screen. How ever image is still sifted to right, so I need to get my sync I guess from somewhere else to get image to sift to the left. Still great info for those who wants rgb to be nearly the whole LCD rgb resolution. I had previously bars on top and bottom and left. Now only right sift issue remains. It seams that rgb is delayed with the sync so image sifts to right.

Where does the megadrive output orginal sync that is mixed with composite after asic?

I am going to test direct rgb output without buffering for now.

EDIT:

It seems I do need to build sync separator circuit and edit horizontal sync signal.