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Thread: I design SuperGun from two Encoder Chip, still work in progress

  1. #1
    rodneyy
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    I design SuperGun from two Encoder Chip, still work in progress

    Hi! I designed Supergun by using 2 encoder IC chip in one supergun, the first one is SONY CXA1645M and another one is AD724JR. Because many Arcade Jamma give you several CSYNC Level and never match with CXA or AD.

    I have been designed Supergun for MVS Arcade by AD724JR. It works!!! and then I try to use with CPS-II and CPS-III. It is really not compatible both of them for the reason..!!!
    1. AD724JR with CPS-II the color so bright
    2. AD724JR with CPS-II the color so mess

    Right now I am re-design supergun by using CXA1645M (I got from electronics store). This supergun full compatible with CPS-II and CPS-III
    The color and image very good shape but when I use with MVS Board. The image so mess and roll all time (I don't know why???)

    Both of my supergun still have only problem with wavy picture. The black color screen will have a little wavy signal. I think it got problem with ground shield.

    I think the problem of Jamma not compatible because CSYNC Level (TTL Sync Level and CMOS Sync Level)

    I must re-design by using 2 type of IC Encoder chip in one supergun and use switch to select them.

    If you have good idea and would like to share , Please kindly to inform me. :pray: Thanks

  2. #2
    Adult Orientated Mahjong Connoisseur ASSEMbler Extreme
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    Jamtex's Avatar

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    Make sure you use Video ground from the board, some Superguns have the Video Ground wired up from standard ground but some boardsets have the video ground seperate.

    Make sure that you keep the distance between the legs of the chip and components to a minimum.

    Use high quality components with low tolerances, use metal film resisiters (they are 1% with a Brown 4th stripe rather then gold or silver striped ones).

    Make sure you have decoupling capacitors between +5V and ground on pins 19 and 12 on the CX chip (and between the power lines of the AD chip). The CX datasheet recommends 0.01uf (ceramic disc type) and 47uf (electrolytic).

    Make sure your Supergun is giving a clean 5V signal under load. This means plugging a board in, switching it on and adjusting the 5V signal until it reads 5.0V, some PSUs will give 5V with no load and then give a different volatage once load is applied.

    Use decent solder, low quality solder will effect the signal and make sure you use just enough to cover the pins to the board.

    The RGB signals must be 1V peak to peak, so try using small pots to clamp the voltage down.

    Make sure you are using good quality cables for the RGB to encoder, use video rather then standard cable to reduce crosstalk.

  3. #3
    Combat Soldier
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    Quote Originally Posted by Jamtex
    The RGB signals must be 1V peak to peak, so try using small pots to clamp the voltage down.
    In my experience most boardsets actually output 0.7Vp-p, which is the standard for SCART. 1Vp-p boards will look washed-out without some conversion, which can as you say be done with a pot for each colour. My ST-V and System 11 (Soul Edge) boards need clamping but the other 20-odd never did. YMMV :)

    Stone

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