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Thread: Removing RGB jail bars idea?

  1. #286
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    for the cable on ebay, what it use to boost the sync cable?

  2. #287
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    and..goodbye jailbars thank you all guys! (pin6 mod)

    i can do the same mod for md1? because i have 3 md1, all 3 modded by removing the cap underside the mobo, but only 1 is 0 jailbars, the other 2 have a little jailbars even after the mod, so for md1 the sony cxa is the same? pin 6 to gnd or what? thanks

  3. #288
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    Quote Originally Posted by Arnold101 View Post
    and..goodbye jailbars thank you all guys! (pin6 mod)

    i can do the same mod for md1? because i have 3 md1, all 3 modded by removing the cap underside the mobo, but only 1 is 0 jailbars, the other 2 have a little jailbars even after the mod, so for md1 the sony cxa is the same? pin 6 to gnd or what? thanks
    Yes, same procedure on MD1, i'm glad it worked for you!

  4. #289
    Sports Talker CkRtech's Avatar
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    Seems like this issue is approaching FAQ territory for all of the different models, mods, and solutions. Good work, guys.

  5. #290
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    So, I had some free time this weekend, and decided to put my oscilloscope on a model 1 high definition model genesis with a CXA1145. There is definitely noise flowing through all 3 video line inputs on the CXA1145 from the internal oscillator. I'm pretty sure everyone was aware of this problem, but thought I'd actually show it. I was in shock at how noisy the video signal actually is

    Top = Blue signal input on CXA1145
    Bottom = Pin5 on the CXA1145



    You can see the noise correlating on both signals and it's extremely bad, a normal video signal will be a very flat line.

    Red doesn't have it AS bad, but is still extremely noisy from the oscillator:



    I didn't scope with pin 6 lifted, because I don't want to touch this genesis yet, I don't have time to mod it this weekend. However, I have another model 1 with pin 5 lifted on the CXA1145, and still noticed some jailbars on the video via RGB. So I looked at the genesis schematic and noticed on the 5313 the RGB signals are sandwiched between a GND pin and a 5V pin. So I decided to scope pin 30 (5v) and pin 29 (B) and found that there is noise from the 5v line causing interference in the RGB signals:

    Top = Pin 29 (B) of the 5313
    Bottom = Pin 30 (5v) of the 5313:



    You'll notice the noise spikes on the 5v lines are correlating with the spikes with the blue signal on the 5313. On my other genesis, I put some bypass caps of 47uF aluminum can, 0.1uF Ceramic, 0.01uF Ceramic between pin 30 and 26 in parallel to see if this reduced the noise and it did. The jailbars were nearly gone and the signal was nearly smoothed out with some very minor spikes. I could only notice the jailbars if I was looking for them. I suspect a lower value ceramic cap probably within the 100pF range would eliminate it completely coupled with the 47uF can.

    It also might be worth putting some very low value ceramic caps between pin 94 and 96 on the 5313 as well.

    Anyways I just wanted to share this finding with everyone as I was just bored one night and decided to figure out what exactly was going on with my genesis. Hope this helps.
    Last edited by Pasky13; 01-20-2014 at 04:03 AM.

  6. #291
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    Quote Originally Posted by t0nito View Post
    Yes, same procedure on MD1, i'm glad it worked for you!
    thanks a lot before i proceed, its sure that for megadrive1 the cxa chip that is different from md2, is the 6 pin to lift and to put to gnd like on md2?

    http://i299.photobucket.com/albums/m...videopower.jpg

    thanks

    like it pasky!

  7. #292
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    Quote Originally Posted by Arnold101 View Post
    thanks a lot before i proceed, its sure that for megadrive1 the cxa chip that is different from md2, is the 6 pin to lift and to put to gnd like on md2?

    http://i299.photobucket.com/albums/m...videopower.jpg

    thanks

    like it pasky!
    Yes same pins, MD2 is a surface mount chip but the pinout is the same. That's how I did it with my MD1, except I have a toggle switch pull pin 6 to GND or to the carrier signal and another to switch frequencies for that carrier (3.58/4.43) and yet another to choose encoding type (PAL/NTSC).

  8. #293
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    thanks how i can remove this 2? i can't pull out the cooler and reach the chip
    Attached Images Attached Images
    Last edited by Arnold101; 01-20-2014 at 01:16 PM.

  9. #294
    Sports Talker CkRtech's Avatar
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    Wow, Pasky13. Eerie that you just posted this as I was thinking just last night that I would like to eventually do a bit of the same thing whenever I finally pull the trigger on my own scope.

    I should also search and download the data sheet for the 1145 since I only have one for the 1645 at the moment.

    You said you didn't scope it win pin 6 lifted, but would you scope it with pin 6 not lifted? The data sheet for the 1645 is pretty particular on the required input specs for that pin, and I therefore assumed that the 1145 in the model one genesis/md is likely to be noticeably off spec whens scoped. While lifting pin 6 is a current solution for jailbar elimination for RGB output, the IC should work properly "as designed" should the input/output specs on the data sheet be met properly.

    Even if the proper components are part of the input circuit, interference from other components of the system due to poor pcb layout (component location) or lower quality components in other areas could cause problems. I can't help but wonder if something along those lines is causing interference in inputs (and probably outputs as well) and throwing off the whole thing.

    I use a Micomsoft XMD-2 breakout box and run RGB Scart off the DIN output of that box in order to run the Genesis into my xrgb-mini, and I don't experience jailbars at all. (At least via RGB).

    It could be that the two solutions for a full cure would be to either
    1: Hobby-up a breakout box as an all-purpose NTSC/PAL output rebuild based on the RGB out from the DIN
    2: Borg-ify the existing 1145 circuit with all of the components needed to eliminate all of the noise and keep the input design in-spec.

  10. #295
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    If I recall correctly, the CXA1665 was basically the 1145 but didn't have the crystal oscillator inside the chip for the subcarrier input, I guess they realized it was a pretty big problem. I don't have a Genesis with a 1165. I only have 2 high definition model 1's.
    Last edited by Pasky13; 01-21-2014 at 04:19 PM.

  11. #296
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    modded the MD1 jap pin6 to gnd, same as removing the capacitor downside the mainboard...a little jailbars on blu still remain instead the same mod on MD2 have totally defeated jailbars

  12. #297
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    Interestingly I am not lying when I say that Using C-sync instead of Composite removed 100% of RGB jailbars on both model 2 and model 1 genesis console for me.
    I am intrigued by why it did not work properly for Arnold.

    I think the difference is either in the TV or in the cable.

  13. #298
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    I can't see any jailbars on my CRT whatsoever. So I hooked up the blue line of my Model 2 MegaDrive and got this:



    It has a noise level that is mostly just a few millivolts. Hardly worth mentioning.

    Are all of you guys that are being plagued by jailbars using flat screen TVs?
    Last edited by KillerBean2; 01-21-2014 at 02:43 AM.
    Bare Knuckle III rules! Also, the music in this game is freakin awesome.

  14. #299
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    I can't see your attachment.

  15. #300
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    Quote Originally Posted by Arnold101 View Post
    thanks how i can remove this 2? i can't pull out the cooler and reach the chip
    That's odd, mine was screwed on I just had to unscrew it

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