MOD GUIDE - Universal RGB-to-YPbPr/Component Circuit & Mod [8/24/2014]

[Game-Tech.US]

Been at it for over an hour...
I have what I think is a great image, but I had to mess with everything to get it.
I also checked to make sure I had good connections at the 6260 from the pin and I mean right at the plastic to the circuit, all 0 Ohm, so that's good.
R2 - 75 Ohm - lower would lighten the still too dark green but top of image starts to tear right, some still seem too bright a shade of green
R16 - 47 Ohm - made a lot of difference putting this back in
R9 - 355 Ohm
R6 - 4.76k Ohm
R7 - 9.25k Ohm
R8 - 4k Ohm
R4 - 1.2kOhm

Does that make any sense? Is it just my TV?
Too be honest it's too sharp!
The colors don't blend together like composite so it looks weird, but I guess that's the compromise...

[thesteve]

lower r2 strengthens green, and weakens sync, thus the tearing (lower r1 would solve)
r16 reduces luma and luma offset (add cap across (470uf) to reinforce if needed)

[thesteve]

r6 and r7 cancel each other, as do r4 and r8

[thesteve]

try this
add 470uf cap across r16 47ohm
r4 and r6 5.6K
r7, r8 12K
r3, r5 2K
all others per schematic

based on the values you posted

[broken]

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.

Would regular polarized aluminum caps be ok, or is a ceramic or tantalum cap really the best choice?

[NightWolve]

Yeah, any cap would work, from my understanding, but if your 6260 chip is on the bottom of the PCB (a US Duo), an aluminum cap will likely be too big when you put that PCB back in place. If you got a Japanese unit and the 6260 chip is on the top, like that first screenshot, then no problem. Ceramic/Tants are the better choice though, and the ceramic won't care about polarity, but they will be more expensive (ceramics >10uF stop being cheap). I noticed that Hudson/NEC used expensive tantalums on the bottom of the PCB and the cheaper SMD aluminums on the top (for the big uF values, of course you had to, as they only came in aluminum, so that had to be designed with space in mind, meaning they had to go topside).

[broken]

Yep, JP Duo-R.

I might have to give this a go this weekend.

Already replaced C961 with a 220uf per thesteve and that made a slight improvement to the jailbars.

[thesteve]

aluminum caps would likely need to be bigger

[broken]

aluminum caps would likely need to be bigger

I picked up some 22uF Tantalums from my local supplier.

[thesteve]

side note
looks like the schematic runs as drawn
just needs some resistor values tweeked (ready for PCB)
may need a resistor and cap at each output jack to reduce dc offset (off board)

[broken]

Finally had a chance to install the 22uF Tants for the jailbar fix.

Works great!

If there are jailbars there now, it's damn hard to tell.

[NightWolve]

Were you getting jailbars with S-Video or a RGB connection ?? Anyway, that's awesome! Supposedly, this is only a problem when tapping RGB, but just checking.

Good work steve, you mad genius!! How the hell this guy took risks with a video chip like that by fiddling around to figure this out I'll never know!

[thesteve]

didnt risk a thing

[broken]

Were you getting jailbars with S-Video or a RGB connection ?? Anyway, that's awesome! Supposedly, this is only a problem when tapping RGB, but just checking.

RGB. I see some very, very faint ones under some specific situations, but it's vastly improved.


Yes, thanks Steve for the great fix!!!

[turbokon]

I just started building this pcb. Still waiting for a few components to come in.