Author Topic: MOD GUIDE - Universal RGB-to-YPbPr/Component Circuit & Mod [8/24/2014]  (Read 19619 times)

NightWolve

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Ok, I have
, but it's way too dark and maybe too heavy on green.
Can you tell me what voltages I should see from signal to gnd on rgb in's, and Y, Pb, and Pr outs?


The RGB input pins are high actually, at 4.66 V according to steve. A really good circuit will kill that all off by the end of it to where you read 0 volts on the output. Industry specs call for 0 to 950 millivolts on Component or general signal outputs (like Composite, S-Video, etc.). You can get away with 1-2 volts though on the outputs (I got a BluRay player that goes 2.66 V max on its Luma line), but if it's 3+ or more, that's borderline bad, not good for the 75 Ohm impedance resistors on the TV/monitor's input module in my opinion (but that's what they're there for, protection), so you'd need pull down resistance and/or output capacitors.

Anyway, that's not an issue for now. See my comments on your youtube video for possible issues other than just reviewing the whole circuit again. Gonna PM steve to chime in on this also, if he hasn't seen it already.

Game-Tech.US

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I get 435mV on Y,
2.25 V on Pb,
2.4 V on Pr.
« Last Edit: January 03, 2014, 04:03:44 AM by akaviolence »

thesteve

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your Y is low
what is R16 set to?

Game-Tech.US

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Ok, yeah removing r16 got the brightness right! Getting real close!
I still think blue is wrong, dark green is almost black.
Y is now 935mV, others unchanged.
« Last Edit: January 03, 2014, 04:04:14 AM by akaviolence »

Game-Tech.US

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Also seeing vertical bars, very undefined. I usually don't see bars in component so i'm sure it's not the tv this time, I almost always see jailbars with composite and svid on this tv.

thesteve

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if you need more trim r11, r12

thesteve

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also the bars are native to the system, solved by 2 caps
http://pcengine.freeforums.org/jailbar-fix-t233.html

NightWolve

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Re: MOD GUIDE - Simple Jailbar Fix a Good Idea if Doing This Mod
« Reply #67 on: March 20, 2013, 12:57:57 PM »
Yeah, good idea to mention this; steve recommends that while one is doing this mod, that you might as well add the jail bar fix that he came up with which turns out is purty simple.

You need two 22 uF capacitors for it (16V rated or better). Solder one to pin 41 and ground, and the other to pin 43 and ground (negative ends to ground obviously if caps are polarized). They happen to be right near where the RGB and Sync pins are tapped, so might as well do it right after. Since the 6260 chip is on the bottom side of a US Turbo Duo, those small surface mount caps would work best in that case, see his 2nd photo here. Japanese units with the 6260 chip on top are much more convenient to work with and using leaded caps would be easier, obviously:



Made this nice one just now, close up, bottom of a Duo:

« Last Edit: June 14, 2013, 04:28:51 PM by NightWolve »

Game-Tech.US

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I don't have any 22uF smd caps on hand, but good to know it's an easy fix....

Game-Tech.US

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if you need more trim r11, r12
It doesn't need any more brightness, but trimming r11 down does make it brighter or wash it out is more like it, trimming down r12 makes it darker, trimming up washes it out just like with r11.
Well post more video in a minute.

Game-Tech.US

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Vid showing dark green issue.
« Last Edit: January 03, 2014, 04:12:35 AM by akaviolence »

thesteve

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r9 will effect green, but will change brightness as well

thesteve

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r7 and r8 are green mix

Game-Tech.US

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I won't say they didn't do anything, but none made dark green look right, still black...

thesteve

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the green input resistor should effect green contrast, the sync input should effect all contrast