Author Topic: Help: RGB internal mods, Vpp measurement, Jamma -> for a Nec XM29plus  (Read 54 times)

Offline juanmiglesias

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Hi guys I want to be sure I'm doing everything right in my setup.

I built a custom RGB connector using a VGA dsub15 connector inside the consoles. I followed the schematics for the RGB -> SCART cables. the I use a regular VGA to BNC cable to connect it to the RGB2 bnc input on the nec.

Everything is working now console wise,  I still need to try the jamma with the Jamma to scart schematic.

I still want to be sure of the Vpp levels. I own a tenma 72-720 oscilloscope, but I'm extremely new to oscilloscopes,  I watched some tutorials on youtube and now I understand the basic functions of an oscilloscope.

I'm using an extron c-video syn sctripper VSS110 to help me with a genesis 2 (tried csync, and c-video), and PSX (using a modded third party scart cable with c-video for sync) which wouldn't want to sync, the snes does sync ok, and the n64 has an internal lm1881. Notice that the VSS110 passes the sync of the n64 and snes without issues, which is great as I can leave it connected.

main Questions:
I saw at retrorgb the csync page that recommends to add a resistor or cap according to the console on the sync line, but if I added the 330ohm on my snes, i would lose sync.
1. does only tv with scart inputs need the resistor, if so why, is it safe to use without it on a NEC?

I added a gbs8220 for mid res boards. no prob there
1. I have an arcadevga - jpac with a PC I want to connect to the NEC, now does the arcadevga outputs 5Vpp? or standard 0.7Vpp?
2. Is anyone tried the Jamma to scart RGB before? does the sync needs the resistor for non scart tvs?

I want to read the Vpp on the RGB lines:
1. do i put the + probe in the R, G, B, individually, and my question after seen some videos, does the ground clamp foes to any ground cable of the av out or hast to go to a different ground spot?
2. what settings on the trigger do I need, I did a little test at channel A: AC, V/div 10mv, TRIGGER: sync on tv, slope +. Using the + on the red line, and the - on a ground line from the av, this was using a PSX scart cable, then adjusted the timesweep and got a dotted slope going from bottom left, to up right of about 1v.
3. is this dotter slope the expected behavior of an RGB line on an oscilloscope or it has to be the continuos waveform you usually see. 
any help would be great.

Thanks in advance!