Cable for modified famicom

[FerdinandoPH]

Hi.
Last year,I bought an original famicom ( modified so it can use RCA), and I have lost the cable with came with it. I have bought a jack to RCA, but it doesn't work well. The video signal is sent through the audio cable and vice versa, and some interferences appear (they appear with the frequency of the music beats)
Does anyone know why does this happen? And most importantly, how do I fix it?

 

[Deleted member 301661]

you mean this mod? https://residualmedia.net/forensics-super-famicom-component-mod/
i think the original cable wasn't stereo jack but phone jack meaning is was enlonged by one segment.
i never heard of this mod, but then again my snes had scart multi out with it original...
i knew about HDMI mod and Super-CIC.
if there's a multi out (not all models had it) see this diagram: https://images.app.goo.gl/EWtDUXkpXKSyKfvH9

 

[FerdinandoPH]

Thank you for your help, but I'm talking about a famicom, not about a super famicom...
Anyway, where can I find a cable with a phone jack to a composite cable?

 

[Ryccardo]

Thank you for your help, but I'm talking about a famicom, not about a super famicom...
Anyway, where can I find a cable with a phone jack to a composite cable?

They're pretty much everywhere ("jack to rca") - but you should figure out the number of pins and pinout before buying

 

[FerdinandoPH]

What's a "pinout"?

 

[Foxi4]

The reason why your signal is dodgy is because the RCA cable isn't properly shielded, and since the interference is consistent with the beats in music I'm going to assume that one of the audio lines is crossing over to your video signal, which does point to a pinout issue.

A pinout is the allocation of functions to "pins", or specific points on the plug. In a typical RCA cable the center pins are the signals while the shrouds are connected to the shield, which is connected to ground. Since the output is modified, you'd have to provide some pictures to explain the issue better. Does your Famicom have a standard setup of a red (Audio), white (Audio) and yellow plug (Video)? You need to ensure that each part of the cable goes to the right point, and with a custom setup you may need a custom cable. We need some specifics about the mod.

 

[Ryccardo]

Yep, the NES/FC has mono sound, so your "jack connector" (before considering anything else jacks exist in three sizes, though most likely a 3.5mm) may have 3 or 4 pins (a ground and 2 signals, the extra one if it exists may be not connected at all, connected to ground, be a copy of the other audio line...)

 

[Foxi4]

It's worth mentioning that not all RCA is equal, we need to establish if this system has a composite (all video on one plug) output or component (Y/Pb/Pr, or Luma, Blue difference, Red difference) output. It may simply be hooked up wrong.

 

[FerdinandoPH]

This is how my famicom looks like:

https://drive.google.com/file/d/1SmoI_qWQGhh80kIOq8G1_peOd5zEZKNV/view?usp=drivesdk

And this is the cable I have bought (which makes the weird stuff I have said before):
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.es/ulk/itm/254289922614

I got the famicom pre-modded from the super potato store in Tokyo

I hope that this information may be useful

 

[Foxi4]

Oofff, I was worried this might be the case. This is a combo, 3.5mm. It's repurposed from an audio plug. The outer sleeve is *usually* the shield, followed by a number of rings, and the pinouts of those are quite varied, especially on a custom system where they may as well be random.



You have at least one part of it working - the video shows up at all, so one part of the cable is soldered correctly, you would have to probe the rest. It's hard to advise you at this stage, you may have to splice the cable yourself and test different combinations until you find a working one. If you can't solder yourself, you can twist the cables and use a termination strip - picture quality will suffer, but it will work. If you don't want to splice for the sake of correct colour coding, you can try playing around with the colours - they're meaningless if you don't know the pinout, you can label them later.

RCA to 3.5mm jack have different standards depending on the implementation and the modder may or may not follow any of them. If I made the cable, I would've put the video on the tip, the audio channels on each of the two rings and the ground on the sleeve, but that's not a rule. If the system had individual RCA receptacles for each signal it wouldn't be a problem, but combo jacks like this are a different story - the cables either work or need to be reworked, it's always a gamble.

It's possible that the reason why your signal suffers is because the original plug had less rings than the current one and the audio signal is crossing over onto the sleeve when in the receptacle. 3.5mm jacks are either stereo or stereo with inline (usually a mic), so either 3 poles or 4 poles. Without seeing the pins of the receptacle you have to guess. If the system is still mono, it could be using a 3 pole jack, which would cause this behaviour (video, audio, ground). Try disconnecting just one of the audio channels and see if the issue persists.



If you look at the jacks, the first ring on a four-pole jack intersects with the sleeve of a 3-pole one - that would cause the audio signal to cross over to the shield, which in turn would pollute the video signal.

 

[FerdinandoPH]

So... Is there any hope left?
I have seen that my cable has 4 pins, so the problem may be that it has to have 3.
If that was the case, where can I find a 3 pin jack to RCA cable?

 

[Foxi4]

I would test if the issue persists if you don't connect the audio plugs first. If it doesn't, test connecting one at a time. If the Famicom is modified for RCA output, but not stereo audio, you may not even need all three plugs. It's not a hopeless situation, you just need to figure out the correct pinout, and buy or make a suitable cable. It's three wires, there are only so many combinations to try.

 

[koffieleut]

I must agree with foxi4 on that one. One of the cables should provide a screen signal.
That's why I mod my consoles myself, then I know where to troubleshoot in case something goes wrong.
Be glad your famicom doesn't have separated sound channels like mine does so Castlevania 3 sounds really amazing

 

[eyeliner]

I would:
Get a male male 1m audio cable.
Cut the thing in half
Expose the wires on each end.

I would get a couple male male RCA cables
Cut those things in half.
Expose the wires

Connect an RCA to the video in in the TV and the audio one to the Famicom

Turn on the TV and Famicom

Merge each pair of wires, testing for video output.

Then would proceed to the audio ones.

I am unsure if the Famicom is stereo, so you would have to search for one audio output.

20 minutes, tops.

 

[Roamin64]

There is no way it uses a 3.5mm headphone jack and that it passes audio + component video. What you simply need is a good quality cable, if the interference persists after that , the mod is to blame. These cables are very common but can range in price from very cheap to very expensive, depending on quality and length. https://www.amazon.com/AmazonBasics-3-5mm-2-Male-Adapter-Cable/dp/B01D5H8JW0

Try searching for "3.5mm to rca" or "stereo 3.5mm to rca". Since the famicom is mono , you only use 1 of the RCA jack for audio and the other for video. Originally you would have a yellow RCA for video , and a white one for audio. White is meant to be plugged in the L (left) audio input of a device. Older devices would copy the left audio channel to the right one when only one was detected so that both speakers would output sound. If you buy a cable with a red a white rca connector , red will become the video.