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N64 video-problem

Started by Majinseed, April 09, 2011, 06:00:06 am

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ok, some facts first: the console is a japanese one, just the 3 cables from the videochip to the av-out. i can't tell wheter or not the pins were lifted from the board or not tough, it came modded and theres a huge blob of glue on the chip.

everything is quite ok, the picture quality is as it should be and all ntsc games run well - i even get PAL-games running without any problems. however, that last part only stands true for my older non-HD Plasma, but not for my newish LCD.
on the new tv its exactly like this: N64 flicker
the problem can be seen quite well in the video: its not a shifting of the picture or some bars running trough but rather a "partial shifting" every now and then. there also doesn't seem to be a timing in the errors.

as said, these errors are only in PAL-mode. the tv correctly reports 576i @ 50Hz and the other tv won't do such stuff.

my guess would be that it has to do with the sync-signal. either the n64 doesn't output a "clean" enough signal and the older tv just can cope with it or the new tv just has a problem with something. now i'd like to find out if i need to buy another TV or can fix it on the n64-side...
tbh i'm a little lost here, dunno how i should verify that its (not) the sync-signal the n64 gives out? ;)

any help appreciated guys - sorry if i forgot to mention anything...


April 10, 2011, 08:31:49 am #1 Last Edit: April 10, 2011, 08:36:39 am by Link83
What video cable are you using? Is it an RGB Scart cable? If so what brand?

Also, how are you running the PAL games on an NTSC N64? Their are some problems in doing that as NTSC and PAL N64's use different crystal oscillators.


well the rgb cable seems to be a no-name product, but no self-made cable. the rgb pins are connected, otherwise i wouln't get a signal at (pins are lifted from the video-chip, i carefully removed the glue to have a look.)

regarding the PAL rom on NTSC machine: atm i'm using the neo myth. unlike other copiers (also tested with the z64) the neo myth seems to successfully bypass the region-lockout. seeing as the region-lockout just looks for a proper CIC of the correct region and as the neo myth can emulate the proper CICs for all games that shouldn't pose a problem. if the region-lockout was the problem i'd either get a "wrong region" message or a black screen...

dunno what exactly could be the problem regarding different crystals, the n64 seems to be able to give out the correct Hz (if thats what you're supposing), which can be verified by hooking the n64 up my other tv.

i specifically suspect that either my tv doesn't match the standarts for the sync-signal or the n64 is outputting a weak sync (or drops it sometimes or whatever). however, i haven't been able to find any info on how i could determine which of those is the case here - mainly because i can't find any info on the signals themselves and because scart seems to be pretty messy and handled sloppy... ideas anyone? ;)


April 11, 2011, 06:42:19 am #3 Last Edit: April 11, 2011, 06:58:56 am by Link83
The question about the RGB cable was because PAL RGB cables have different components on the Composite Video line compared to NTSC RGB cables. If you had an official Nintendo cable this could cause problems, as its third party I dont know how its been wired or if it uses any components (Resistors, Capacitors) so you may have to do some testing if you want to confirm that.

Scart usually gets the C-Sync signal from Composite Video. Early NTSC N64's do also have a separate C-Sync output but I have never seen it used, and Nintendo removed C-Sync output from N64 motherboard revision NUS-CPU-04 and onwards.

The X1 crystal oscillator also provides a clock signal to the RCP-NUS co-processor as well as the video encoder, take a look at the 'Clock Generator' section from Nintendo's patent:-

This does cause timing issues between NTSC and PAL games, although the hertz rate is still set to 50Hz or 60Hz depending on the game (or ROM's) region code.

I have loaded Zelda OoT Master Quest (NTSC/60Hz ROM) on a Neo Myth using a PAL N64 and that resulted in popping/crackling in the audio due to the timing differences, and it wouldnt surprise me if different games have different issues depending on how they were programmed.


April 11, 2011, 08:23:54 am #4 Last Edit: April 11, 2011, 10:38:57 am by Majinseed
well, here's the complete pinout of the cable. there shouldn't be any resistors in there, at least i weren't able to measure any...

Multi AV (Cable Side)

Red| Green| Composite Sync| Blue| GND| GND| S-Video Y (Luma)| S-Video C (Chroma)| Composite Video| +5 Volts| Left Audio| Right Audio
1 2 --- 4 5 --- --- --- 9 10 11 12
15 11 --- 7 18 --- --- --- 20 8 / 16 6 2
Red| Green|| Blue| Blanking-GND|||| Composite Video| Status / Blanking| Left Audio| Right Audio

Scart (Male)

all the info about the pins were taken from http://www.gamesx.com/wiki/doku.php?id=av:nintendomultiav and http://pinouts.ws/scart-pinout.html

@ the 60Hz issues: as you said that seems to depend on the software, 1080 (which i tested) didn't seem to have such problems...


April 11, 2011, 08:48:09 am #5 Last Edit: April 11, 2011, 08:51:31 am by Link83
No offense but I think you must have made a mistake - 5V cant be connected to Composite Video, if it was you would not see any picture at all since there would be no sync signal for the TV. Apart from that the cable seems to be wired up correctly.

Does this N64 used any sort of RGB amp? I hope it doesnt use the 'internal boost' mod where you link two points together on the VDC-NUS chip - its shown at the bottom of this page in the picture with two red dots:-
This most definitely causes problems.


you are right, i've switched the connections of 9 and 10, the post above is corrected now.
additionaly i found that pin16 seems to have 75 ohm which slipped on me before...

and: no, the n64 does not have the two points bridged.


April 11, 2011, 11:25:23 am #7 Last Edit: April 11, 2011, 11:41:02 am by Link83
Pins 8 and 16 are often linked via a resistor (Usually 100-180 ohms) when only a +5V signal is present, as its the simplest way to enable Scart switching without a +12V signal:-
Although as you can see, this usually makes the TV default to its Widescreen setting.

The two points used in the 'internal boost' mod could be linked on the top or bottom of the motherboard, basically it connects pin 24 of the VDC-NUS chip directly to ground. If you feel comfortable checking continuity between pin 24 and ground you can double check that this hasnt been done.

Another possibility is that maybe the ENC-NUS chip doesnt really like having its RGB inputs removed? Or perhaps your TV just doesnt like the pure C-Sync signal which it is being given (If you lift the RGB output legs on the VDC-NUS chip then there is no RGB input to the ENC-NUS video encoder chip, so it will only output a C-Sync signal. Composite Video and S-Video output are disabled since there is no RGB input)

Apart from that i'm at a loss to explain the problem, it might just be one of those times where you have to play PAL games on a PAL console and visa-versa :(


well, its not the "internal boost" for sure, they aren't connected. i connected them on another console and tested if that helps, but no luck...
i am led to think that it has to do with the missing rgb info in the composite signal, but before trying to get the hot glue off (and most probably breaking the pins during remmoving it) i'll go and try a booster-cable. less invasive :)

i'll post again if i find anything new...

edit: oh, and thanks again ;)


April 12, 2011, 07:28:03 am #9 Last Edit: April 12, 2011, 07:31:02 am by Link83
Just had one other thought - are you connecting the Scart cable directly to your TV, or through a Scart switcher? I once had a Scart switcher that caused sync problems, but only when there was a bright white screen. When I connected the Scart cable directly to the TV there were no sync problems at all.

Also, if you want to try an RGB amp you might want to use Viletim's amp design, since it kind of requires you to lift the chip legs (Or remove SMD components):-
The other option would be Baku's amp design:-


i posted two more videos. i weren't able to get/built an booster cable yet but had a few minutes yesterday - so i decided to test what would happen if i reconnected the rgb pins to the mainboard.
the problem still persisted, but i were able to see the following when connecting the NTSC-n64 via my normal european av-lead:

N64 flicker composite-part1
N64 flicker composite-part2

i guess the b/w is normal, but what might be of interest is the flicker that can be seen every now and then - its not really visible in the videos, but it even (partialy, at the affected positions) changes the color to some kind of violet while the flicker happens.
it should also be noted that i did the "internal boost" because i've connected both, rgb and the mainboard at the same time.

another thing: my european n64 will play both, PAL and NTSC games just fine on this tv. no problems at all...


April 20, 2011, 02:14:25 am #11 Last Edit: April 20, 2011, 12:15:48 pm by Link83
If you have performed the 'internal boost' mod then you can expect flicking interference like that - I know from personal experience. The 'internal boost' actual connects the VREF input of the chip directly to ground - this is very bad and will eventually result in the chip burning up. It can also cause permanant damage to the VDC-NUS chip (If you touch it with your finger after it has been on for a while you can feel that it runs pretty hot) I did mention previously:-
Quote from: Link83 on April 11, 2011, 08:48:09 amDoes this N64 used any sort of RGB amp? I hope it doesnt use the 'internal boost' mod where you link two points together on the VDC-NUS chip - its shown at the bottom of this page in the picture with two red dots:-
This most definitely causes problems.

It even says in the guide "there is a quick and easy internal amplification mod - although this can sometimes cause interference on the screen."

I am afraid you have just replaced one type of interference for another, and it doesnt really help narrow down the cause :(

Also, its worth noting that PAL AV cables are different to NTSC AV cables as they have a 75ohm resistor to ground on the Composite video signal:-
All official Nintendo PAL AV cables have this resistor, but not all third party cables include it. I dont know if your cable has a resistor or not, but it could be another factor to consider?


I think N64s' sync signals are a bit weak / nonstandard overall. I have 2 N64s and they both have issues with my projector which is quite sensitive to sync. The unmodded PAL N64 has similar issues to the first video, losing the sync every 10th second or so (using composite/s-video). The second machine (RGB&region free modded) works fine with PAL games but NTSC games (60Hz) won't sync properly at all, the projector stays in 50Hz mode instead. I've tried LM1881 and some sync boosters but with no luck. All my other consoles work OK with proper cables, although one late revision NTSC SNES I've tested was similarly locked to 50Hz by the projector.

I've considered buying a XRGB-unit along with a new TV, what i've heard they should be able handle nonoptimal sync signals well. I think I'll be needing one anyway, as most new flat TVs have awful input lag in 480i/240p modes.