# Fairchild Channel F RGB notes

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Posted (edited)

So after driving myself crazy looking at what is going on it this circuit it appears

That only four pins of the 71445 set color. Its confusing because the methods they use are hard to follow.

On the data sheet it even has pins specified R, G, B someplace else. To put it short those pins do not matter for our uses; and will not give you RGB

Looking at how A and B go to pin 2 and 14 of the 74153 we can deduce that B is a lower value, A is higher, and A and B is highest.

Nothing (00) is black or blank idk; for my uses it doesn't matter.

This is because without A or B being a logic one you won't have either of the burst amplitudes applied, aka no color so either white or black.

That means to get color out you can only have 3 bit combinations on A/B 01, 10, and 11

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D C B A

D = A3; C =A2; B=A1; A=A0

0101 RED
0110 BLUE
0111 GREEN

0010 LIGHT BLUE
0011 LIGHT GREEN

1001 GRAY
1000 BLACK

0000 nc < ONE OF THESE MUST BE WHITE

0100 nc < ONE OF THESE MUST BE WHITE

WHEN OTHERS PROBABLY AN ERROR OR BLANKING EITHER WAY NO COLOR

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Somebody should validate this if they can confirm/deny. I am not too sure about white atm.

I need binary or decimal values for the RGB color palette.

Uh I may have mixed up light blue/green and full blue/green

Edited by the_crayon_king

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Posted (edited)

So RGB should be able to be taken from the 9322 (C2)

For my uses I am calling

pin 12 = Di

pin 9 = C

pin 7 = A

pin 4 = B

D is inverted from how you would see it at the 74145 thus the "i"

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truth table

DCBA

1000 = 0 NC >
1010 = 1 NC >
1001 = 2 > blue light
1011 = 3 > green light
1100 = 4 NC > White ?
1110 = 5 > red bright
1101 = 6 > blue bright
1111 = 7 > green bright
0000 = 8 > black
0010 = 9 > grey

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I could explain my logic but basically white is either 1000 or 1100.

I did a first pass at trying to make a schematic for this:

https://easyeda.com/hotdog6394/fairchild-chan-f-rgb

TBH doing this with a FPGA would be far simpler. However, where is the fun in that ?

Issues I am having is finding a pallet with decimal rgb values. I set 255 (714mv), 191 (534.8mv) and 0 (0).

I only want to bother to set combinations of 3 specific values., so if someone has better values to shoot for let me know.

This is the colors with what I have (randomly) chosen so far: [note this is not on the console (yet) just a color representation of what should be possible with the above circuit]

Edited by the_crayon_king

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