MV-1C RGB + Sync Maximum Vp-p values

Pasky

Pasky

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So, I was unable to achieve a solid color screen for each individual color. So I got the next best thing which was an all white screen. At pure white, all colors are at their maximum output (255,255,255). So with this in mind I took a scope to the MV-1C using this screen:



So the results are:

Green: 3.80 Vp-p
Red: 3.52~ Vp-p
Blue: 3.52~ Vp-p
Sync: 4.0~ Vp-p

Most other consoles output to a television set at 1.7Vp-p~ (becomes 1/2 with the 75 inline resistor so effectively 0.85 is the result).

So with that in mind, the resistor values to get a 0.85Vp-p for each individual color line (assuming a 75Ω to ground in the tv) is:

Green: 260 Ω
(http://www.wolframalpha.com/input/?i=0.85+=+(75/(75+x))+*+3.80)

Blue: 235~236 Ω
(http://www.wolframalpha.com/input/?i=0.85+=+(75/(75+x))+*+3.52)

Red: 235~236 Ω
(http://www.wolframalpha.com/input/?i=0.85+=+(75/(75+x))+*+3.52)

Scopes of the color lines:
Spoiler:

Blue:


Green:


Red:



Sync:




EDIT:

Unsure if I scoped these with a load on the color lines. These may be less than their true values, I'll test again later.
 
Last edited:
BeefJerky

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Pasky said:
So, I was unable to achieve a solid color screen for each individual color. So I got the next best thing which was an all white screen. At pure white, all colors are at their maximum output (255,255,255). So with this in mind I took a scope to the MV-1C using this screen:



So the results are:

Green: 3.80Vp-p
Red: 3.52~Vp-p
Blue: 3.52~ Vp-p
Sync: 4.0~

Most other consoles output to a television set at 1.7Vp-p~ (becomes 1/2 with the 75 inline resistor so effectively 0.85 is the result).

So with that in mind, the resistor values to get a 0.85Vp-p for each individual color line (assuming a 75Ω to ground in the tv) is:

Green: 260 Ω
(http://www.wolframalpha.com/input/?i=0.85+=+(75/(75+x))+*+3.80)

Blue: 235~236 Ω
(http://www.wolframalpha.com/input/?i=0.85+=+(75/(75+x))+*+3.52)

Red: 235~236 Ω
(http://www.wolframalpha.com/input/?i=0.85+=+(75/(75+x))+*+3.52)

Scopes of the color lines:
Spoiler:

Blue:


Green:


Red:



Sync:


Click to expand...

YsEU2oz.gif
 
Xian Xi

Xian Xi

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That makes so much more sense. I thought I was nuts when I started to notice that I had to turn green down just a bit more than Red and Blue to get a nice white balance.
 
Xian Xi

Xian Xi

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Can you check an AES as well? Tapping from where RGB is tapped internally and from the AV socket? I'm wondering the difference.
 
mikejmoffitt

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I don't quite get how this happens - The output stage for each color is identical and for a solid white screen I would expect the same results. It's interesting that the voltage was not consistent across the channels.
 
Pasky

Pasky

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mikejmoffitt said:
I don't quite get how this happens - The output stage for each color is identical and for a solid white screen I would expect the same results. It's interesting that the voltage was not consistent across the channels.
Click to expand...

Do you happen to have a schematic of the color channels before they hit the jamma pins for the MV-1C?
 
Pasky

Pasky

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Ah I see, it's just using a resistor ladder. I haven't really poked around much, I know the MV-1C contains the SNK ASIC and assumed the DAC was inside there. I've actually got a board that's not assembled I could take a look at. It's mostly the reason I didn't trace back as my CMVS is mounted and to look at traces running through via's under the board would require me to unplug a lot of shit.
 
shadowkn55

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mikejmoffitt said:
I don't quite get how this happens - The output stage for each color is identical and for a solid white screen I would expect the same results. It's interesting that the voltage was not consistent across the channels.
Click to expand...

He's using a screen that is perceived to be white. It may not be completely white from a digital standpoint. You can duplicate the DAC and force all the input bits to high if you want to do a control group.
 
Pasky

Pasky

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shadowkn55 said:
He's using a screen that is perceived to be white. It may not be completely white from a digital standpoint. You can duplicate the DAC and force all the input bits to high if you want to do a control group.
Click to expand...

Ya unfortunately, I have no 100% way to verify if the screen is indeed true white internally. I simply edited the color palette on the Japanese warning screen and changed it to 0xFFFF and verified it with a color dropper using a capture card.
 
shadowkn55

shadowkn55

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Pasky said:
Ya unfortunately, I have no 100% way to verify if the screen is indeed true white internally. I simply edited the color palette on the Japanese warning screen and changed it to 0xFFFF and verified it with a color dropper using a capture card.
Click to expand...

The color should be 0x7FFF for complete white. 0xFFFF is all the RGB bits set with the darken bit active.
 
Pasky

Pasky

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I was under the impression the last bit did nothing. Wasn't aware it was the darken bit. I didn't think it would affect the color output. Does it? I know world heroes used it but wasn't sure for what purpose.
 
shadowkn55

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Pasky

Pasky

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Thanks, I'll have to wait until I can make a test rom or some other method before I have a concrete controlled test then. Until then, take the measurements for what they are I suppose.

Thank you both for all the information.
 
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