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Voultar MD1 RGB Bypass on VA4

Home Forums Repairs and Mods Voultar MD1 RGB Bypass on VA4

This topic contains 12 replies, has 4 voices, and was last updated by  infidelity 1 week ago.

Viewing 13 posts - 1 through 13 (of 13 total)
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  • #24092

    nzChris
    Participant

    Has anyone been able to get the Voultar RGB bypass board working on a VA4 PAL board?

    I’ve followed the instructions and checked continuity of every connection but am getting ‘no sync’ on my OSSC or direct into TV.
    I have tried this on two VA4 consoles and now neither of them work.

    Here is an updated photo with signals now pulled directly from the chip as Voultar recommends, since this photo I have also moved the power and ground directly to the 7805 (furthest away from the DIN).

    View post on imgur.com

    #24198

    BuckoA51
    Keymaster

    We’ve actually been seeing some strange things with PAL Mds and sync and we’re still investigating.

    #24214

    nzChris
    Participant

    Ok thanks, hopefully it’s something simple = )

    #24556

    renovigo
    Participant

    Hi,

    As a matter of fact, I found a way to connect the Voulat board and get a decent picture.

    There are a few differences to take in consideration toward the installation guide :

    – First, lift RGB pins on the VDP (the big tricky part) but leave the SYNC one on the board, don’t lift it. You can connect the Voultar board to the corresponding pads, and also connect the CSYNC pad to the CSYNC pin on the VDP.
    – On the back of the board, discard the mainboards pull-up resistor for the CSYNC signal and install a 2k2 resistor as it’s shown in the installation guide. As well Locate Pin 10 of the CXA1145 on the solder side and cut the track as shown in the guide. We will not cut anymore pin on the CXA1145.
    – Finally, we need to connect RGB out of the Voulatr board directly to the 8 pin DIN. Again, on the back of the board, locate R, G, and B of the DIN connector and solder them to the RGB out wires of the Voultar. Concerning the SYNC out, you can solder it directly on the SYNC leg of the DIN connector on the upside of the board.
    – For +5v and GRD, take them on the 7805, as you did.

    The results are pretty good, even on a CRT screen.

    Voilà !

    #24562

    nzChris
    Participant

    Hi Renovigo,

    Thank you for your reply, I have had this project on hold for the past month now with no progress.
    This evening I managed to get it to work after seeing a number people connecting the +5v to the csync on the voltar board with a 2.2k resistor as below.

    All of a sudden I have a signal on my OSSC and it is operational.
    The colours are now vibrant, but there are huge vertical lines everywhere, I assume these will be corrected by swapping out the SMC components to the new values Voultar has suggested.
    I bet if I tried your way it would have worked also so thank you for taking the time to respond.

    cheers,
    Chris

    #24572

    nzChris
    Participant

    Okay it seems like the issue was resolved on the newer version of the board!

    https://voultar.com/index.php?route=product/product&product_id=73

    https://voultar.com/image/cache/catalog/SegaRGB-500×500.jpg

    You can see on the newer boards the +5V has a link to the CYSNC and the component values have been updated also.
    Hope this helps someone else as I’ve been scratching my head for a long time.

    Chris

    #24585

    nzChris
    Participant
    #24596

    renovigo
    Participant

    Hi,

    Thanks for the information Chris. I didn’t see there was a new revision for the board, and I’m glad you find a solution on your own.
    But do your last post shows the image you get ? Because it seems that there are still some interferences isn’t it ?

    #24600

    nzChris
    Participant

    Yes this is what it looks like now, with the new revision the capacitor values etc have been changed so I am assuming these would fix the lines. TBH I cant figure out how and where to buy the smd components so I have ordered the new board direct from Voultar.

    #24649

    nzChris
    Participant

    Ok this should be my final post, I chatted with Voultar and managed to get it working.
    The last part of the puzzle was lifting pin 50 on the VDP which is the redundant subcarrier.
    You might not be able to tell from the photo but it is razor sharp and not even a hit of jail-bars to be seen in any light.

    View post on imgur.com

    #24656

    renovigo
    Participant

    I’m glad you made it finally ! It looks perfect to me.
    Something I find strange though, is that in my case I didn’t have to add an extra resistor on the board itself. I did have the pin 50 lifted but I get very fine results with no extra routing on the Voultar board. Would it be better if I did add some ?….I’m maybe a little lazy to re-open the console again…

    Anyway, well done !

    #25645

    renovigo
    Participant

    Hi,

    It’s just an information post, following this thread

    I removed completely the CXA1145 on my VA4 PAL MD, as it has an rgb bypass, I followed some installation clues I saw on the internet (here for example), telling myself that it worth the try -and it kind of made sense regarding the all bypass purpose-.

    So I did it. And it worked indeed. BUT it didn’t worked everytime.

    Everytime the console ran for more than 20 minutes maybe, once you turn it off and change the cartridge, the system didn’t boot anymore. No picture, no sound, nothing.
    The weird thing is, if that happens and you open the console to see what’s happening and try to “repair” (checking voltages, make fresh solder, etc.), it can boot again ! You can play for 30-40 minutes. But again, when it turns off, it doesn’t boot anymore.

    SO, if I would advise something for people who are installing an rgb bypass to a VA4 MD PAL system, DON’T REMOVE THE CXA1145. I guess this chip makes more than just video encoding, maybe some clock purposes or whatever. Or maybe it works only on NTSC systems.

    If anybody encountered the same issue, or on the contrary, didn’t faced any problem at all, feel free to share !

    Thanks !

    #26221

    infidelity
    Participant

    Hello I have a question regarding a bypass that I’ve done last year,using one of the first bypass amps released (its green and has 3 vertical capacitors)

    My system is a model 1 VA6. My method I performed, was lifting the R,G,B,Csync pins from the VDP off of the motherboard, soldered cdrom audio cables from those pins, to the bypass amp. I also have pin 50 from the VDP cut.

    The picture I get from my ossc with firebrandx’s 320×224 optimal timings is incredible!

    With that said, I still have very very faint vertical lines,they are really noticeable on a light gray background, example being the hidden stage select screen for Altered Beast.

    Now, i did this before Voultar released his version of the bypass. I have removed the 3 pull up resistors on the bottom of the motherboard, and I’m bypassing the CXA Sony chip entirely.

    Why, when I’m running directly from the VDP, to the bypass amp, am I still getting vertical lines? What am I missing, or need restored?

    I’m using a euroscart rgb cable wired for csync.

    Please help, thanks!

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