PS1 C-sync help

Discussion in 'Modding and Hacking - Consoles and Electronics' started by Bax, Apr 30, 2015.

  1. Bax

    Bax Member

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    I'm trying to mod my consoles to output C-SYNC instead of composite video and preferably without using a sync stripper. On my fat SCPH-550x (PU-18 board) I've got it working by lifting the composite video out leg on the CXA1645 RGB encoder chip and connecting c-sync to the pad below the leg. Like this:

    schematic.png
    photo.jpg

    Now the problem, I have no idea what would be the best solution in regards to voltage levels, impedance and so on. Before or after the 2.2k resistor? Any additional components or maybe a bad idea to begin with?

    pin10.png
    pin20.png

    I've also seen suggested:

    C-sync straight to AV Multi out #6. Then cutting the composite video trace.
    Haven't tried this. http://www.absolute-playstation.com/api_faqs/faqrgb.htm
    C-sync -> 75ohm resistor -> 220uF electrolytic capacitor -> AV Multi out #6. Then cutting the composite video trace.
    I tried this at first but the video was too dark and went darker when video brightness increased. http://www.mmmonkey.co.uk/?wpdmact=process&did=MzIuaG90bGluaw==
    CXA1645 Leg 20(Composite video) straight to AV multi out #6.
    No idea what this is about!?! http://gamesx.com/wiki/doku.php?id=av:playstation_1_sync

    Anyone knowledgeable who can shed some light on this? I would appreciate it!

    Edit: adding some mod instructions below to clarify.

    Method 1:
    • Heat and carefully lift up leg #20 on the CXA1645 chip, so that it no longer makes contact with the pad below.
    • Solder one end of a wire to the little via/hole marked "C-SYNC before 2.2k" in the picture.
    • Solder the other end of the wire to the pad(see picture) slightly diagonally below of leg #20.

    Method 2:
    • Carefully cut the composite video trace at the AV multi out pin #6.
    • Solder one end of a wire to the little via/hole marked "C-SYNC before 2.2k" in the picture.
    • Solder a 75ohm resistor and a 220uF capacitor to the wire(positive leg towards via, negative leg towards multi out).
    • (or solder these compontents inside the RGB scart cable, to the scart pin #20 wire instead).
    • Solder the other end of the wire to the AV multi out pin #6.
     
    Last edited: Dec 13, 2015
  2. bacteria

    bacteria I am the Bacman

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    For C-Sync, (like for RGB), you can use composite, or luma from S-video. If you're talking about sync-stripping, then you're probably referring to H-Sync and Y-Sync like you have with VGA mode; in which case an adaptor you can get on ebay, composite (or S-video) > VGA, is probably what you want as by definition it has to strip C-Sync into H-Sync and V-Sync to work.
     
  3. Bax

    Bax Member

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    Thanks for replying, I just watched a few of your videos :) My goal is to mod my consoles or cables to use RGB and Composite Sync as sync, without the Composite Video. One reason for this is the Nintendo 64 and PS1 having "crosshatching" issues when using Composite Video as sync, plus I found C-Sync to work more reliable than Luma or CVID on monitors/scalers. I'd prefer to use a Sync Stripper only as a last option.

    I probably shouldn't be experimenting with this stuff in the first place but I couldn't find a solution online that worked for the PS1 and I've read that wiring C-Sync straight to the output could be a bad idea. So if I'm not mistaken, what I've done above by lifting the CVID output leg on the encoder and "reusing" the components along that trace is:

    A) C-Sync signal from GPU -> Wire -> 75ohm -> 220uF -> AV Multi Out.

    But there's also the option to connect the C-Sync wire after some additional components (at encoder pin 10):

    B) C-Sync signal from GPU -> 2.2kohm -> 5pF? to GND -> Wire -> 75ohm ->220uF -> AV Multi Out.

    Anyway, I have since tested some more and Option B is too dark and doesn't work correctly. Option A is working fine so far, I'm just unsure if it's acceptable in terms of voltage levels, current draw, not blowing stuff up, etc.
     
  4. ynoS XSP

    ynoS XSP Rapidly Rising Member

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    I find this thread very interesting because I am trying to do the same thing and I have encountered exactly the same problems.
    My 1084S D1 (by Daweoo, not Philips) only displays a correct picture when using Composite Sync. If I use CVBS or Luma for Sync some lines at the top don't show straight and become wavy over time. Using an Lm1881 to clean Luma seems to work but I have long wanted a simple cable solution only, even if that meant modifying the console.

    The same happens to me, and I think this way is not the proper one.

    When performing a similar modification on a Sega Saturn model 2 I followed the tracks from jumper pair 16/17 and realised that Composite sync comes straight out from the sega VDP! Although the same "GPU -> 2.2kohm -> 5pF? to GND" arrangement exists on the sega board before Composite Sync enters CXA1645, the fact is Composite sync is fed directly (raw) to AV port upon changing jumpers.

    That lead me into thinking that is logical to do the same on the playstation board, even if here signals have to be tapped from somewhere since sony provided no jumpers on the board to make things easier.
     
    Last edited: Jul 26, 2015
  5. ynoS XSP

    ynoS XSP Rapidly Rising Member

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    That is the big question, but unless someone has measured it before we still don't know the raw peak-to-peak voltage and if the effect of having a 75 ohm resistor/220 uf coupling capacitor inline makes the signal in accordance with scart specification. On the other hand, I have no clues about the possible stress caused on the Sony GPU and if it could cause damage driving the Comp Sync signal directly to monitor and bypassing the RGB encoder.

    But if adding a 75 ohm resistor plus a 220uF capacitor makes monitor/TV to sync correctly then the signal must be being treated to an "acceptable" level, I suppose.

    Of course I maybe wrong, the sega VDP on the Saturn can be different from the Sony GPU and that made Sony discard the option of having Comp. Sync straight out?

    Follow me on this:
    Remember the fact that Sega MD1 has Composite Sync incorrectly linked to CXA1145 pin 10 when it should be pin 11?
    Well, if pin 10 is 'Sync In' then it must be composite sync coming from one of the VDP's on the MD board, so it's raw Sync, right?
    The official sega RGB adapter for MD1 is the 3085 model which uses amplifier transistors on the small circuit board in the middle of the cable.
    Assuming someone at sega was aware of the pin 10 / pin 11 issue then perhaps that circuit was designed to give proper signal treatment to Sync (and R,G,B) signals so that, at least VDP would be lightly loaded?
    I am starting to think that we should use a similar approach when dealing with Composite Sync directly from VDP or GPU.
     
    Last edited: Jul 26, 2015
  6. ynoS XSP

    ynoS XSP Rapidly Rising Member

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  7. MonkeyBoyJoey

    MonkeyBoyJoey 70's Robot Anime GEPPY-X (PS1) Fanatic

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    The GPU in the Saturn does not produce analog video, only digital. The DAC converts the signals to analog. It uses a standard DAC which can be bypassed and combined with an FPGA to get HDMI. OzOnE's universal HDMI board can do that.

    As for the PS1, I found this guide for getting C-Sync on a PS1: http://gamesx.com/wiki/doku.php?id=av:playstation_1_sync

    It's for the SCPH-7501 and the PSOne but it does show where to get C-Sync on the SCPH-5000 series. If you have a monitor or upscaler that supports 15KHz RGBHV (VGA), you can get a better picture using H-Sync and V-Sync instead of RGBS.
     
  8. ynoS XSP

    ynoS XSP Rapidly Rising Member

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    Thanks MonkeyBoyJoey,

    Bax and I have already figured out where to get composite sync from the PS1, however we are unsure about the proper way of connecting the signal to a TV/monitor (specifically, the 75ohm resistor and 220uF capacitor).
    Could that be the right way?
     
  9. MonkeyBoyJoey

    MonkeyBoyJoey 70's Robot Anime GEPPY-X (PS1) Fanatic

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    Your welcome.

    I'm not sure about the cap and resistor. I heard something about just using a 75ohm resistor but nothing concrete. I'm planning on doing a VGA mod to my SCPH-7501 and I'm going to add C-Sync so I can use RGBS in case nothing I have works with 15KHz RGBHV. TriMesh might know since he has been very helpful with my other PS1 mod plans. It seems really hard to find proper info on getting C-Sync out of the PS1.

    If all else fails, we could create a new C-Sync signal by combining H-Sync and V-Sync. To do this, run H-Sync through a 1N4148 diode and then run V-Sync through an 820 ohm. After that, simply connect the two signals together and you now have C-Sync. I wonder if there would be a difference between the on-board C-Sync and the sync combiner C-Sync?
     
  10. ynoS XSP

    ynoS XSP Rapidly Rising Member

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    Now that you mention it, I think the 1084S D1 I have supports H-Sync and V-Sync on the DB9 plug at the back.
    Could there be any improvement (picture quality?) by using separated Sync instead of Composite Sync?
     
  11. MonkeyBoyJoey

    MonkeyBoyJoey 70's Robot Anime GEPPY-X (PS1) Fanatic

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    It should be better quality. If you could get it working, can you post some comparison screenshots? Modern LCDs can be modified to support 15KHz however no one seems to be able to show me how to mod them every time I ask about it.
     
  12. Unseen

    Unseen Spirited Member

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    No.
     
  13. ynoS XSP

    ynoS XSP Rapidly Rising Member

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    Oh well, I will stick to Composite Sync then.

    Anyway, I decided to do the modification to my ps1:

    Fotografia1651.jpg

    Fotografia1646.jpg

    Fotografia1649.jpg

    Fotografia1648.jpg

    So, now I have Composite Sync (before 2.2k resistor) routed directly to AV port pin where CVBS used to be (I cut the track). Don't mind about that black strip of insulating tape, it's covering a modchip someone previously installed.

    Since I had one of those Blaze PS2 component cables laying around I also decided to do an experiment with it.
    I dont't think the Blaze cable has outer shielding (aluminium foil or copper braid) but I suppose every line R,G, B, CVBS, Left and Right are individually shielded (and even then perhaps it's nothing special considering how "thin" each wire looks). However, assuming this could be benfitial I bought one of those cheap scart adapters and modified it a little so I could use it to couple each signal to the monitor/tv scart input.

    I removed the switch on top and made use of the "hole" to route L and R audio breakout cable and +3 volts for blanking signal coming from 2 AA batteries (all my CRT tv's have a manual switch to AV mode).

    I included inside the 220uF caps for RGB and the 75ohm+220uF cap for Composite Sync:

    Fotografia1636.jpg
    Fotografia1640.jpg
    Fotografia1641.jpg
    Fotografia1642.jpg
    Fotografia1644.jpg


    Oh, and yes, it works. :)
     
    Last edited: Jul 31, 2015
    MonkeyBoyJoey likes this.
  14. ynoS XSP

    ynoS XSP Rapidly Rising Member

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    I have just been doing some reading on RetroRGB site and at some point he states that Sony CXA1645 outputs Composite Sync... What does he mean? That we could tap it directly from the chip just like in the CXA1145P?

    1645CompSync.JPG

    As anyone confirmed this?
    In that case which pin is Comp. Sync out? :confused:
     
  15. MonkeyBoyJoey

    MonkeyBoyJoey 70's Robot Anime GEPPY-X (PS1) Fanatic

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    That's for a Genesis Model 3. Is that what you are trying to mod? If so, it might be easier to get a VA1-VA6.8 model 1 Genesis/Mega Drive. Avoid the VA7 model 1 at all costs. It's a horrible abomination to Sega hardware.
     
  16. ynoS XSP

    ynoS XSP Rapidly Rising Member

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    No, it's just that I find puzzling that Genesis Model 3 uses the same RGB encoder (CXA1645, as in the PS1 and Saturn) and someone is stating that it outputs Comp.Sync in that system, contradicting the datasheet and the PS1/Saturn need to hack the signal from the board.
     
    Last edited: Aug 7, 2015
  17. retrorgb

    retrorgb Spirited Member

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    MonkeyBoyJoey is right - I'm talking specifically about the Genesis 3. Also, I've only tested a handful of Genesis 3's, but I was able to get csync by tapping the "sync in" (pin 10) of the CXA1645 on the versions that didn't already output it to the multi-out. When I have time, I'll re-word that page to be more clear...but it doesn't have anything to do with the PS1.
     
  18. ynoS XSP

    ynoS XSP Rapidly Rising Member

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    Oh, ok then.
    Sorry, it seems I was thinking about the chip itself and not the chipset.
    Thanks for the explanation!
     
  19. retrorgb

    retrorgb Spirited Member

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    No problem...and I'm sorry if the page wasn't clear enough.
     
  20. Helder

    Helder Site Supporter 2014,2015

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    On the Genesis schematics the VDP supplies the CSync that goes into the encoder and branches off that pin to the AV socket.
     
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