N64 RGB mod too bright.

[Mark]

Hey guys, I hope it's alright that my first thread here is one asking for help. I promise I've done my due diligence and won't waste your time.

I've performed the well-known N64 RGB mod using the Texas Instruments amplifier chip. The output of my mod is very bright, however. I've checked all over the internet with Google and can't find someone else with this same problem, which is why I started this thread. My N64 is NTSC. Here's a picture to illustrate:



That's the title screen of F-Zero X. Here's what it looks like when I simply skip the chip and connect wires to wires through a breadboard. This picture was taken after the preceeding image, proving the N64 isn't totally broken and isn't the root cause of the problem. Obviously the image is darker than it should be.



I've tried the mod without AND with 75 ohm resistors on each output line. I've tried the mod without AND with the capacitor bridge. The result is always the same: a completely blown-out image.

I'm getting 5V+ from the multiout pin. I'm grounding to one of the two multiout ground pins. I've checked my lines multiple times.

The SCART cable I'm using is a SNES RGB cable from the now-seemingly-defunct Retro-Accessories folks (their domain expired and I think they closed up shop). It's worked great for an entire year. Here's what it looks like internally, in case anyone was curious.



Any ideas, ladies and gentlemen? Thank you for you time.

EDIT: I forgot to mention I had two THS7314 chips and I mounted and tested both in the same setup. Both exhibited the same symptoms. Perhaps Mouser sent me a bad batch?

[fagin]

You need to reduce the voltage on the RGB lines. Beef up the resistance on the lines.

Did you amp the sync as well.... if you did, try it without the sync being amped.

[Mark]

You need to reduce the voltage on the RGB lines. Beef up the resistance on the lines.

Did you amp the sync as well.... if you did, try it without the sync being amped.

I didn't touch the sync line or cut any traces.

I will try some fatter resistors instead of 75 ohm and post results.

EDIT: Tried 330 ohm resistors, made a little difference. Guess I'll go down to my local 'shack and buy a random grab bag and try a few more.

[Darksakul]

Try putting potentiometers on the Red, Blue and Green Lines.
Then Manually adjust till you get the right output.

Beats the hell out of guessing what resistors to use.

[RGB32E]

Where are you tapping RGB, +5VDC, and ground from?

[Darksakul]

Where are you tapping RGB, +5VDC, and ground from?

He said "I'm getting 5V+ from the multiout pin". So from the Multiout A/V connector.
So I am guessing the same +5 that the scart uses.

With that said, @Mark can we see photos of your Mod and wiring?

[RGB32E]

He said ...

Not very constructive replying to that.

It's likely that he lifted legs instead of tapping RGB from the underside of the PCB. He should have followed this:

[Mark]

He said ...

Not very constructive replying to that.

It's likely that he lifted legs instead of tapping RGB from the underside of the PCB. He should have followed this:

I did lift the legs on the chip. Should I attempt to lower them back to the board again and tap from the other side?

[Mark]

Where are you tapping RGB, +5VDC, and ground from?

He said "I'm getting 5V+ from the multiout pin". So from the Multiout A/V connector.
So I am guessing the same +5 that the scart uses.

With that said, @Mark can we see photos of your Mod and wiring?

Here's some pictures.

http://imgur.com/a/FHMiK

Blue = Black wire (except the ground wire)
Green = Green
Red = Orange wire (except the 5v+ wire)

Like I said up above, I tried with and without resistors. The pictures don't show all the different configurations I tried, just the first one. Tried 470 ohm, that's still too bright. Good thing I have like a billion more resistors to try!

[Fudoh]

the only interesting pic's missing - where you tapped the RGB signal.

[Mark]

the only interesting pic's missing - where you tapped the RGB signal.

Yeah well it was from the raised legs of the chip. I just lowered the legs back onto the pads again and removed the wires from there. I'm going to attach fresh wire to the other side of the board where you indicated instead. Be back with pictures and a report. Thanks for the help so far.

[Mark]

Double post/bump to let you guys know I'm a dumbass and getting the signal from the other side of the board results in a perfectly working N64 RGB amp modification. Had to reseat the legs on my chip though since I raised them, and somehow the green leg's pad had burnt away so I had to make a new one from the root of the pad to the leg itself. Thanks for your help duders. Time to play the only shmup I know of on the N64!

[Fudoh]

Now if only Star Soldier was any better Play Bangai-oh instead. That's what I play right now. Such a great game.

[Mark]

Now if only Star Soldier was any better Play Bangai-oh instead. That's what I play right now. Such a great game.

Looks like it only got released on XBLA over here.

[opt2not]

Now if only Star Soldier was any better Play Bangai-oh instead. That's what I play right now. Such a great game.

Looks like it only got released on XBLA over here.

Region Mod your N64 and import that bitch

Or play it on your DC...

Also, nice work on getting it sorted.
I've got an RGB mod on my to-do list for my N64 as well.

[Star1]

Sorry to reply to this old thread, but I guess I'm the second guy to have this problem!
Although the solution seems clear, I'm curious as to what the difference is between connecting the amp directly to the lifted legs compared to connecting it to the points on the underside of the board?
Is it simply that the latter has the signal being routed through a set of resistors (C124-C126)?
If so, does anyone know what their values are?