Can't get RGB modded n64 to display properly on XRGB3 ...

I have an RGB modded NTSC n64.

I also have a XRGB3 with latest (english) firmware.

I connect the two with a SNES SHVC-010 cable.

I am using the settings for the N64 that are recommended here:

http://junkerhq.net/xrgb/index.php/XRGB-3#Recommended_settings

Specifically, B0 FPGA, LPF=off, 7 sharp, A/D=150.

The results are, I can see the n64 output on the screen, but it is scrambled - kind of like the PPV channels used to be scrambled on old cable TV. I can make out screens of mario 64, but just barely. Also, the picture goes in and out of sync and it keeps flashing "15 khz" in the upper right every once in a while.

What am I doing wrong here ?

 

Do you know how your N64 is modded? Chances are the XRGB is not receiving composite sync from your N64. Since you have an official cable the prime suspect is the mod work. Most modders will be using SCART which uses composite video in lieu of composite sync so it's pretty typical to either overlook composite sync entirely, or use it inappropriately and hope for the best.

 

Do you know what RGB mod method was used on your N64? What SCART cable are you using and has it been modified at all?

 

I have never owned a XRGB3, but if its designed to take RGB scart input - it needs to accept composite video as sync.... as thats how pretty much all rgb scart cables are?

Making a device that accepts RGB scart, but not in the way its actually used by everyone is just madness surely?

 

That sounds like a problem with sync.

By the way, the XRGB3 doesn't use SCART, it uses the Japanese RGB standard, which uses the same connector but has a different pinout. Thus you need an adapter to connect a SCART cable to an XRGB3. I believe the cable the OP is talking about is the Japanese SFC RGB cable, which is wired for Japanese RGB, so it should work (unless it uses composite video as sync). I believe the XRGB3 only accepts composite sync.

 

That makes sense. Didnt know Japan's scart was different (googled pinout and it certainly does look like it only uses CSYNC)

 

Ok, so the cable is the right (japanese) one, so it appears the mod is bad ? I had it done by this guy:

http://www.consolegoods.co.uk/

He does this all the time, so I would think he'd have done it correctly. If sync is off, could it just be a single lead, or wire, that is disconnected ?

 

The mod isn't bad*, it's just not good for people that don't use SCART. CSYNC is a single wire, but I do not advise you to wire it directly from the DAC output labeled CSYNC unless it's confirmed to have a TV level output (requires an oscilloscope to test). I don't know, but I think it's a logic level output, which means it SHOULD be attenuated to the TV level. Some people, such as almost everyone using the LM1881 chip in mods, feed the logic-level CSYNC directly to the TV, which might work since TVs are generally very resilient, but it's a very dumb practice because in the N64's case you'd be asking the DAC to supply 3.3 V / 75 ohms = 44 mA of current which a logic output certainly can't do. The proper way is to build a resistor-divider network** with matching impedance so the TV gets the expected sync level, the DAC only has to supply around 4 mA, and the signal is terminated preventing reflections and ringing.

*Well it most certainly is bad in terms of technical integrity, few modders design their own circuits, and fewer to professional standards nevermind installation. If the mod just wires the DAC outputs directly to the A/V connector it's a very bad mod since there is always meant to be support circuitry.

**I posted a circuit for this here somewhat recently but I don't remember which thread it's in, it might have been for 5V operation so it'll need to be adjusted to 3.3V. (Note to self: I'm destitute yet bad modders get paid, I should probably reevaluate things.)