[PGM] Solved... Vpp readings on RGBS lines

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    • [PGM] Solved... Vpp readings on RGBS lines

      Hi. So! I am currently working on consolizing a PGM system and need some help fine tuning the progress.

      I would like to build an RGB buffer to ensure correct RGB levels are output from the system.
      My approach is the same as outlined in this thread - amplify or divide RGB line voltage to 0.7Vpp as input to a THS7374 amp.
      For that I need to know the Vpp of the R, G & B lines (Sync would be nice too...).

      So... do any PGM owners happen to have an Oscilloscope on hand?

      I need readings from a white screen...
      Demon Front - white screen during intro.
      KOV2:9D - plenty white screen moments during intro.
      PGM screen test - R,G,B,White colour bars... 1/2Vpp??

      While I'm not exactly doing anything that hasn't been done before, this is my progress so far:



      System runs fine on 5v alone. No audio as the amp runs on 12v, but able to tap sound directly from the UPD6379 DAC.
      Left and Right audio then fed to a @tawy NeoGeo MKL audio amp. Seems to work great!

      Anyway - hope someone can help out on the RGB front...please let me know if you can!
    • some multi meters can do peak voltage.

      being JAMMA though it should be 0V-4V on the R,G,B lines and sync should be a 5V square wave.

      there is some discussion on dropping the RGB peak voltage to 0.7v here that you may find useful: JAMMA to VGA and JAMMA to SCART
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      The post was edited 1 time, last by twistedsymphony ().

    • So..turns out my local library has a workshop in the basement...
      And that workshop comes with...an analog oscilloscope!



      I think this is the reading I need... But then i have never used a scope before and they guy who does was on holiday..
      Its a start!

      ...

      Looks like 2.3Vp-p :D

      The post was edited 2 times, last by nam9: I was 0.1v out... Not bad considering I had no idea what I was doing... See below. ().

    • nam9 wrote:

      So..turns out my local library has a workshop in the basement...
      And that workshop comes with...an analog oscilloscope!



      I think this is the reading I need... But then i have never used a scope before and they guy who does was on holiday..
      Its a start!

      ...

      Looks like 2.3Vp-p :D
      if your scale was set to 1V/div, the yes ;)
    • Ok. What a difference 1 week and a few YouTube videos make..



      RGB lines: 2.4Vp-p (0.5v/Div, 10μs/Div)



      Sync line: 5Vp-p (1v/Div, 10μs/Div)

      That should be enough to allow me to properly attenuate video signals.

      Next Up: How to solve the 'shifted to the right' image issue...
      Any takers?



      Thanks again for the input!