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Thread: RGB Bypass of a JROK Encoder (on a supergun)

  1. #1
    Akari's Big Brother
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    RGB Bypass of a JROK Encoder (on a supergun)

    I am thinking of picking up an RGB monitor to use vertically since decent vertical cabs are kind of hard to come by around here.

    I already have a decent supergun for breaking out the controls and power but it has an old JROK encoder in it. It works great for NTSC but of course if I have an RGB monitor, it would be best to bypass the encoder.

    So my question is, if I just hooked up a fingerboard between the pcb and supergun, could I just pull RGBS from there and leave the supergun untouched? Or do I need to add a switch to disable the encoder?

  2. #2
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    Someone correct me if I am wrong but I believe the JROK uses a CXA1645 or a CXA2075. It should just be a matter of soldering to the RGB out pins on the encoder itself and passing them through a 75 ohm resistor and 220uf capacitor. For the CXA1645 and CXA2075 red out is pin 23, green out is pin 22, and blue out is pin 21. That would get you RGB out and keep the S-Video/composite circuit intact.

    Sorry for the really bad picture. I don't have one of these encoders to take a picture myself so I pulled it off the JROK website. Judging by how the capacitors are laid out on the pcb and comparing them to the application circuit these should be the pins you are looking for.

    Last edited by Skips; 05-17-2013 at 12:54 AM.

  3. #3
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    Very interesting question. I hope somebody knows about it with tech detail.
    The guy in this site (http://hacks.slashdirt.org/supergun.html) claims that without a chip like the AD8073 video amplifier the input impedance to the encoder may be changed. I think the input inpedance to the RGB monitor is changed as well if You keep the encoder connected, so the AD8073 is acting like an isolator (I wonder this chip has the 75 ohm driver integrated on the output).
    Well... err... maybe this whole thing is not realy necesary. Nobody points to use an isolator circuit when modding an AES for RGB bypass after all, so shunting the signal should be Ok.

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  5. #5
    Akari's Big Brother
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    Awesome, thanks guys. That's a much more elegant solution than what I was thinking about.

  6. #6
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    I wonder if there's a way to do the same thing with the Neobitz encoder. It's possible?

  7. #7
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    Quote Originally Posted by Rotten Zombie View Post
    I wonder if there's a way to do the same thing with the Neobitz encoder. It's possible?
    Not that I know of. The AD724 does not have RGB out.


  8. #8
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    You could always just replace it with a different encoder with a similar pinout.

  9. #9
    JammaNationX
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    Quote Originally Posted by Rotten Zombie View Post
    I wonder if there's a way to do the same thing with the Neobitz encoder. It's possible?
    For the Neobitz I haven't seen a huge impedance issue running RGB out from the encoder, some people put an off/on switch on the power to the Neobitz for RGB use.

  10. #10
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    Xian, Skips, thanks for the answers.
    Cheers

  11. #11
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    I have a MK30 Adcap by Jasen and it uses an Jrok too. Picture looks fine on the framemeister, but is totally strange (to dark, first lines are wavy ...) on the sony bvm. I have to use a extron and activate ddsp to get a perfect picture.

    so the suggestion would be to ad resister and cap to each color (r g b)?

  12. #12
    JammaNationX
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    Quote Originally Posted by nio View Post
    I have a MK30 Adcap by Jasen and it uses an Jrok too. Picture looks fine on the framemeister, but is totally strange (to dark, first lines are wavy ...) on the sony bvm. I have to use a extron and activate ddsp to get a perfect picture.

    so the suggestion would be to ad resister and cap to each color (r g b)?
    If you are talking about the lines at the very top, sounds more like a convergence issue. You might need to adjust the BVM.

  13. #13
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    Its the first 10-20 lines. But the are perfect when i use and extron with ddsp on.
    But its also the color. pciturexis too dark and white is acting strange.

    And the peoblem is only wirh this supergun that has the jrok inside, other guns work fine.
    Last edited by nio; 03-19-2017 at 02:54 AM.

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  15. #15
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    already in the line, sync striker from arcadeforge

  16. #16
    Rugal's Thug

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    I have this same problem, also shown here: (not my video and its long and boring)
    https://youtu.be/_dkZKf86rh8

    My question is just. Will this solve my problem?

    Quote Originally Posted by Skips View Post
    Someone correct me if I am wrong but I believe the JROK uses a CXA1645 or a CXA2075. It should just be a matter of soldering to the RGB out pins on the encoder itself and passing them through a 75 ohm resistor and 220uf capacitor. For the CXA1645 and CXA2075 red out is pin 23, green out is pin 22, and blue out is pin 21. That would get you RGB out and keep the S-Video/composite circuit intact.

    Sorry for the really bad picture. I don't have one of these encoders to take a picture myself so I pulled it off the JROK website. Judging by how the capacitors are laid out on the pcb and comparing them to the application circuit these should be the pins you are looking for.

    Last edited by nio; 03-21-2017 at 12:49 AM.

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  18. #18
    Rugal's Thug

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    Thanks for trying ro help me!

    Wirhe rewire you mean adding the resisotr and capacitor to the rgb line or completly bypassing the envoder for rgb?

  19. #19
    JammaNationX
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    Quote Originally Posted by nio View Post
    Thanks for trying ro help me!

    Wirhe rewire you mean adding the resisotr and capacitor to the rgb line or completly bypassing the envoder for rgb?
    No, I mean rewire the supergun because something in there isn't wired correctly causing those problems. If he's using the same encoder I use then the resistors/caps are already there. That mod only applies to the JROK 3.1 which doesn't have RGB pass through but the 4.1 (that has component) already has RGB pass through.

  20. #20
    Rugal's Thug

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    Thanks for being so patient with me!

    I think I understand now!

    I die some more research. It is either the psu or the wiring to ground:

    http://shmups.system11.org/viewtopic...1cc8&start=480
    Last edited by nio; 03-21-2017 at 01:26 PM.

  21. #21
    JammaNationX
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    Quote Originally Posted by nio View Post
    Thanks for being so patient with me!

    I think I understand now!

    I die some more research. It is either the psu or the wiring to ground:

    http://shmups.system11.org/viewtopic...1cc8&start=480
    Wait, you're telling me he didn't do that? Oh wow, no wonder people have problems with his superguns.

  22. #22
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    I cant realy tell. I did a video of my issue

    just tried a different psu which causes a lot od interference.

    but without extron and ddsp on the gun is unplayable for me:

    http://youtu.be/W9eJ3YKhDP4

    i turn off the ddsp at about 0:10-0:11 and back on from 0:18-19

    my setup is:
    - mk30
    - cable to sync striker from arcade forge
    - extron
    - sony bvm d20 with rgb

  23. #23
    JammaNationX
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    Quote Originally Posted by nio View Post
    I cant realy tell. I did a video of my issue

    just tried a different psu which causes a lot od interference.

    but without extron and ddsp on the gun is unplayable for me:

    http://youtu.be/W9eJ3YKhDP4

    i turn off the ddsp at about 0:10-0:11 and back on from 0:18-19

    my setup is:
    - mk30
    - cable to sync striker from arcade forge
    - extron
    - sony bvm d20 with rgb
    Easiest way to check is with a multimeter with continuity test. Put one probe on the earth ground and the other on the data ground, if it says it's connected then it's another problem. If the case is metal, it should be connected to earth ground, too. But I'm sure how he wired those things up.

  24. #24
    Rugal's Thug

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    I did all the measurements and it seems fine. I get about 0.7 ohm resistance between the different grounds.

    Thanks a lot for your help and showing me where to look at!!!

    I found that the Extron causes the real issues in my setup and I removed it. Now I need to fix the sync issues of my 4-slot.

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