Trying to understand the YPbPb circuit for the NESRGB board.

[numbski]

I'm trying to wrap my head around how this circuit functions, and my electronics-fu just isn't there.

I get that it takes the luma signal from the main NESRGB board, and then it takes the RGB lines (no sync, or sync-on-luma?) and somehow generates Pb and Pr lines.

This is all I have right now - but I guess I was trying to decide if I could make a general-purpose circuit out of this, or in combination with say the CXA2075, swiping the luma from the generated s-video signal.



The two caps are probably just buffers - but even looking at the datasheet for the SGM8052, I can't make heads or tails of what is being done here.

http://www.icbase.com/File/PDF/SGM/SGM00241010.pdf

[numbski]

Here's the resistors marked up. I'm guessing that "?" is a diode, but again - not terribly certain. Since it has polarity I can't think of it being anything else.

[Woozle]

The component with a question mark is most likely a ceramic capacitor used to "bypass" the power supply rail, its probably in the 0.1uF-10uF range if I had to guess based on size.

[numbski]

Being completely unmarked isn't helpful.

I need a meter with a decent capacitance tester function.


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[Syntax]

The component with a question mark is most likely a ceramic capacitor used to "bypass" the power supply rail, its probably in the 0.1uF-10uF range if I had to guess based on size.

Yep looks like a 100n cap used to filter noise off the power rail, if either side is - + that is.

No need to check its value, 100n(104) ceramic is fine for that purpose.

[Woozle]

If you Google the datasheet for that IC you'll find that pin 8 is the voltage/power supply, that's what the unmarked component is connected to. The other side (top side) of the component looks like it's going through a via to the ground plane.

99% certain it's a ceramic cap used to bypass the power supply rail to remove ripple voltage.

[VEGETA]

Hello,

are you certain of these resistor values?

I got my board but it has some color issue either from Pb or Pr since Y alone is fine. I suspect that some resistors are bad due to heat and so on but checking via multimeter while resistors still on board is not reliable since they connect with other stuff which alters the read value.

plus, I guess I cannot take RGB from NESRGB output RGB pins right?

EDIT: I have checked all resistor values and they seem fine. However, I destroyed my component board pads, thus will be getting a new board. it seems that either the opamp is broken or anything else.