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Thread: Connecting an Arcade PCB to a CRT TV

  1. #91
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    ah yeah, had done the schem view too:

    Full res: https://imgur.com/NHqoTVh

  2. #92
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    Thanks for the info guys and thanks for the offer to help Kaizen, I will try and look at this on the weekend.

  3. #93
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    Quote Originally Posted by MarkOZLAD View Post
    Just looked through some of my notes for the Panasonic MX-3 chassis. This is one @djcalle and I have looked at before. From the factory there are not caps on the RGB lines. We believe the addition of some 0.1uF caps would be helpful.

    My other notes...

    RGB:

    "Teletext board removed. Jumper Sync. Remove R622-624. Use 300 Ohm as mux resistor, twisted with 75R and into holes from removed resistors"

    Blanking:

    "Blanking signal into E9 header. >1.0V. 5V regulator is IC807."
    Finally got a chance to look at this.
    I have opened the TV and got the PCB out. Looking over it I have found the resistors to remove, there is no Teletext board fitted. I will add some 100n mono caps. I can see IC807 is a +5V regulator so do I just need greater than 1V? eg. just connect +5V to the blanking pin or do I need a resistor? I will feed the sync to the comp video via a 1K resistor. For the RGB lines how to I connect the 300R and 75R resistors. Is it like the attached image - where the 1K would be 300R. Finally where do I jumper Sync?
    Thanks
    OSD-Mux-RGB-Circuit-v2.png

  4. #94
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    You could put a resistor on blanking, something anything from 1k to 10k should be fine.

    Sync goes into AV port.

    "Remove R622-624. Use 300 Ohm as mux resistor, twisted with 75R and into holes from removed resistors"

    Leg of 75R goes to the grounded hole, leg of 300 goes to the jungle, twisted legs are the RGB injection point.

  5. #95
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    It was raining today so it was a good opportunity to work on this.
    I added 100n caps to the removed links, the 300R and 75R resistors to the removed 900R resistor spots, 1K resistor to the comp video input, 5V from IC807 pin 3 to the blanking pin without any resistor.

    Fired up the TV with a SMS2 RGB out.
    Got a good picture but colours slightly off.

    Tried a Pandoras box 5S with a good picture but slight rolling to fast rolling sometimes.
    I turned off the TV and looked online if there was a service mode to access vert adjust. I did find service mode info online but unsure if there are any vert adjust etc.
    I repowered the TV and watching the picture which had been on for maybe 20secs the tube switched off. TV still powered up eg LED.

    I loaded the remote setting into my Harmony remote and I can turn the TV on or off but there the tube is not on and I don't see a glow from the neck.

    Maybe there is a fault with the TV? Someone just gave it to me last month so I don't know the history of it.
    While it was working the picture did look really good with the Pandoras box.

  6. #96
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    Ok the Panasonic TV is no go but will be good as a tube donor but thanks for the help on it everyone for my first crack at it.
    My next TV is an NEC N3456
    I managed to find the Schematics for it.
    nec_ct-1420_sm.pdf_1.jpg
    Should I disconnect the output of the OSD from the micro and inject the RGB from there? Also on the same chip is Blanking which states 5.6mV.
    Any help on connecting up the RGB would be great.
    thanks.

  7. #97
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    Do you have a link to the schematic in PDF format.
    The attached image starts to get pixelated when zooming in.

    I think you should be abled to donthe mux mod and keep the OSD.
    Namco Starblade - Taito Cocktail 14" x 3, 20" x 2 - NZ SI PtII Upright - Chase HQ DX, Taito Top Speed - Taito Grand Champion - Taito Safari - LAI SI Head to Head Cocktail - SI Cocktail Clone x 2, Pong Clone x 3

  8. #98
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    Using @MarkOZLAD's excellent spreadsheet tool, i calculate you want 680R resistors in each of the RGB lines. Let's see if i've finally got my head around this

    Remove the OSD grounding resistors 118, 119, 114. Replace the 0.01uF cap next to the jungle for pins 25, 27, 29 with a 0.1uF cap (+ve toward the jungle if polarised) then add the 680R resistor in each line going to the cap, then connect whichever RGB input line to the far side of the cap, and from that same point a 75R resistor to ground. Then for the blanking line, remove the ground-side leg of factory grounding resistor R719 at 1K, and drop your 5V blanking signal into that loose leg.

    This is assuming the jungle on that schematic plays ball. Looking at the datasheet it's listing a straight DC voltage of 2.5V for the RGB input pins 25,27,29. Like it's a bias voltage and not a peak-to-peak value, which might make things interesting. I'm hoping MarkOZLAD can weigh in with some thoughts

  9. #99
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    I wouldn't change the caps, I never have before.

    Are R114, R116 and R118 through hole or surface mount?

    I created a lookup table for the OSD mux resistors. I rarely use my spreadsheet.



    It says to use 750 Ohms as the OSD mux resistor, though 680 Ohms is likely fine.


    If it turns out the R114, R116 and R118 are through hole we can use the "twist with 75 Ohm resistor" method as I got the 8 Bit Guy to do in his video. If not you'll likely want to make a little board or something, perhaps try and find a text port.
    For blanking, seeing as this is for arcade....If R113 is through hole, just lift the leg of R113 that is closest to IC101 and inject 5V into the lifted leg.

  10. #100
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    Thanks for all the info everyone, I will check out the PCB in the TV and see how it matches the schematic and also if its surface mount components or not.
    Also here are all the files I found on the TV.
    The image did go funny when zooming in but the next time a looked at it it was ok? Anyway I converted it to PDF if that helps, the file is also with the rest of the files here.
    https://www.dropbox.com/sh/hkg9tmqaz...TgCbM_R6a?dl=0

    Edit: The downloaded image was PNG with a JPG extension, fixed now.

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