N64 THS7316 Picture is very bright - no proper attenuation

[moldov]

Colleagues,

I'm finishing my setup of retro consoles, OSSC upscaler and SCART switches.

All is mostly done with scope and proper meausurements and I got the best picture I ever saw since I switched from emulators back to real things.

Everything is awesome apart of N64. The picture is very-very bright even I have level of brightness on my TV turned to 0.

N64 is RGB modified with THS7316. I attached the inputs of THS7316 to capacitors and resistors which has the same contact point to RGB pins of VDC-NUS. I connected to C122, C123, C124

The picture is not mine but I have the similar connection





Also I have 75 Ohm resistors on output of THS7316. I attached 1.2 Kohm resistors to THS7316 RGB inputs in parallel and connected together to the ground like I've done on SFC Jr - no changes the picture is very-very bright.

I didn't change 75 Ohms resistors yet, but it's not correct solution I guess. I need to attenuate the signal on input side of THS not on output side.

My N64 is japanese. Also the composite picture is very-very bright too. I was looking through internet trying to find the solution, but I managed to find only 1.2 Kohm solution which doesn't fit my console.

Could You help me to resolve it somehow.

[maxtherabbit]

was the composite output over-bright before you installed the mod?

also you know you can't use PAL region RGB or composite cables with an NTSC console, right?

[moldov]

Hmmm, good question actually. But I cannot say for sure was it bright or not. I didn't check it actually.

Regarding PAL region - yes, I know that cables are different (12V).

But composite cable is the same I guess. It's just RCA cable no resistors or capacitors inside. Resistors and capacitors being installed when RGB is being used. As far as I know.

[Link83]

But composite cable is the same I guess. It's just RCA cable no resistors or capacitors inside. Resistors and capacitors being installed when RGB is being used. As far as I know.

Actually thats not correct - official NTSC composite cables are straight through, but official PAL composite cables have a 75ohm resistor to ground on the composite video line, and on later models a 220uF capacitor as well.

[paulb_nl]

First things first, you need to fix composite being too bright first. Did you check the 7316 for shorts?

[moldov]

But composite cable is the same I guess. It's just RCA cable no resistors or capacitors inside. Resistors and capacitors being installed when RGB is being used. As far as I know.

Actually thats not correct - official NTSC composite cables are straight through, but official PAL composite cables have a 75ohm resistor to ground on the composite video line, and on later models a 220uF capacitor as well.

I didn't know that actually. But aparently I have NTSC cables because they are imported from Japan with the same time with consoles.

[moldov]

First things first, you need to fix composite being too bright first. Did you check the 7316 for shorts?

I removed the mod completely to be sure it was s not affecting composite picture



So, as You might see, with Brightness set to 0 I cannot see Mario Faces on the Select File screen.

I guess it has to be like this:

[James-F]

Was it okay before the mod?

[paulb_nl]

Can you post a picture of the bottom of the mainboard?

What resistance do you measure for R8-R10 & R11?

[moldov]

Colleagues, thanks to everyone for Your proper support.

paulb_nl - You are the Prophet!!!!:))) Once again You helped me to fix the issues. For sure it was short circuit again. I was not the one who was installing the mode - it was friend of mine. While measuring R11 resistance, accordingly with Your advice, I found a little spot of solder on it, shorting both ends of the resistor. I removed the shortage and image is crystal clear now!!!!! So, 1.2 Kohm resistors on input lines of THS7316 are not required, only 75Ohms on the output lines need to be installed.

Also I got the bad experience guys. Don't repeat it. While checking the console without the case I INSERTED JUMPER PACK WRONGLY. And 12V and 3.3 Fuses in PSU are not showing good resistance now. Instead of showing something like 0 Ohms they showing about 30 Kohms. Now I know that Nintendo was using resettable fuses and it takes time for them to set themself to initial state. I've been waiting for 2 days and still waiting when the resistance will become 0. Seems it takes days or even weeks. I'll update the post in case I will be able to power up that PSU again.

Before that experience I didn't knowt that such kind of fuses even exist. So - be really careful and attentive while installing Jumper Pack into the console without the case.