A/V modded original Famicom has no extra sound with FDS

[lobdale]

Sorry I'm starting a thread as my first post!

Basically, I got an A/V modded Famicom from a store in Osaka about a year ago and it has pretty bad jailbars, but I've kinda put up with it.  Anyway today I got an FDS and sure enough playing Doki Doki Panic there are no extra sounds (no enemy tossing animation, enemy hit sounds, etc.).  So does this mean the mod was just done incorrectly?  Is there some way for me to fix this so that I have all the sounds?  If I use an RF adapter will that do it?

So confused...

[Xious]

This means the sound output is wired to the audio pad, rather than the mixed-audio connection. Please view:

http://www.atariusa.com/RetroVideo/docs

This will illustrate the correct location to derive the mixed-audio signal. 

[lobdale]

This means the sound output is wired to the audio pad, rather than the mixed-audio connection. Please view:

http://www.atariusa.com/RetroVideo/docs

This will illustrate the correct location to derive the mixed-audio signal. 

Thanks very much for the answer.  I actually cracked this baby open tonight to see if I could switch something from the pad to the pin, and here's what I've been presented with:



Link to full size: http://i.imgur.com/e1TBe.jpg

Along with lots of glue.  So... is there anything I can do here or am I pretty much stuck with it?

[Xious]

Yes, however that photo is of the wrong part of the modification (the video amplification circuit). Look for a second modification, probably on the lower-right quadrant: There is an audio pad, that should be wired to the positive axial on a capacitor, and that to the RCA audio wire.

Break the connection between the capacitor and the 'Audio' pad, then solder a jumper wire between the capacitor (the axial that you removed from the 'Audio' pad) and the mixed-sound output pin, which is illustrated in the manual for the RetroVideo kit. 

[lobdale]

Yes, however that photo is of the wrong part of the modification (the video amplification circuit). Look for a second modification, probably on the lower-right quadrant: There is an audio pad, that should be wired to the positive axial on a capacitor, and that to the RCA audio wire.

Break the connection between the capacitor and the 'Audio' pad, then solder a jumper wire between the capacitor (the axial that you removed from the 'Audio' pad) and the mixed-sound output pin, which is illustrated in the manual for the RetroVideo kit. 

I think I must have been confused using the images from the RetroVideo kit, as it says the mixed audio pin is the third in on the side with the ribbon cable, which is on the top.  It also shows an audio pad next to that, whereas on my board there is only a hole (seen in the upper left of this image).  There is indeed, as I remember, a single cord running to the lower right part of the board, though right now I'm at work and can't recall what is going on down there.  I so, so appreciate your help with this, you guys are like wizards on this thing.  Once I get back home I'll crack this puppy back open and see what we have down there and get a picture up here to make sure I am resoldering to the right pin, since I obviously had an issue before.

PLEASE WAIT
Post Merge: July 05, 2011, 03:06:41 am
The saga continues!  Here's what I've got in the lower right corner.



It looks kinda like the wire (the white part) is indeed soldered to the "SOUND" pad under there, but then there's some other wiring (copper braid) that looks like it's just been haphazardly soldered over two pins right next to it.  Is that insulation soldered for grounding purposes, or something else?

I guess two main issues for me remain then!

I need to desolder the white wire from the pad, solder it to a capacitor, then solder a wire from the capacitor to a pin, right? So,
1. What kind of capacitor/strength?  I'm living in Japan with limited knowledge of capacitors, so it'd be nice to know what that is.
2. Which pin exactly do I solder the wire coming off the new capacitor to?
and
3. What the hell do I do with that copper braiding that has been bridged over those two other pins?

Thank you so much for your persistence in helping me solve this odd problem.  I picked up Zelda 2 today and it's just not the same with 8 seconds of silence at the beginning ;_;

[Xious]

The copper-braid is the shielding of the RCA wire that is (or should be) soldered to a ground point. It's probably safe where it is.

The other wire (white) should be connected to a capacitor (0.45uF to 1uF will suffice; 1uF is the de-facto standard) and then jumpered to the mixed audio output pin which is the third pin in from the edge of the board on that 'ribbon-cable connector'. The RetroVideo manual illustrates it and marks it as 'Sound' and 'Mixed-Sound' on pages 10 and 15 respectively. 

[lobdale]

You are truly a life-saver.  I've been slowly chipping away at this project for a while now, accumulating FDS games in the process...  your tips have once again brought some value to this thing.  The hard part now will just be to figure out where to get a capacitor here.  

I assume it would be alright for me to just clip the white wire off and leave the stub soldered to that sound pad, right?  I can throw a piece of electrical tape on it, strip part of the white wire and resolder to that without bothering to desolder from the pad and maybe wreck it up in the process.  Not that it's a hard job, but why do what I don't have to?

Does it matter what end of the capacitor I hook up to the white wire?  Based on your previous post I assume it should go

RCA White wire (-) --| |-- (+) -----jumper wire---- third pin from left on upper left of board

Sorry for what are likely stupid questions, but most of my solder-work in the past has just been wire-to-wire or wire-to-pin and I've never really worked with capacitors before.  I assume I solder them onto a wire just like soldering a wire to a wire.

Anyway, hoping for some success here and I'll be sure to post some progress later!

[Xious]

Actually, the way I wrote about it reads poorly and I didn't mean for it to sound like that, but I re-wrote several parts of the reply because I was tired and in a bad mood and after reading it, I realized it'.d come across as being stuff or possibly even rude, though such was never my intent.

Thus, I decided to try fine-tuning it, and somehow when I edited the sentence I really mangled it or I was just out of my mind for a second. Honestly though, you can wire it backwards and it'll still work for this function; you could even get away with a standard cap (non-polarized) for this job, though the correct way is, with one of my happy ASCII-schematics:

• Note that I use C2 and CN2 here, as C1 and CN1 are video-side components the way I do things and I want to maintain consistent notation and references.

                C2 ~1µF         CN2 (RCA Connector)

• ------------ -)|+ ------|   |------\
  Mixed Sound             |   |       |== RCA Shield
  Output Pin              |---+---------- Central RCA Pin
                              |       |== RCA Shield
    [CE]----------------------|------/
  GND Pad                     
                                           (ASCII/X|S)
  Famicom Audio Amplification Circuit for A/V Conversion
  
  
  

[lobdale]

Well, it's done!  I was able to find a 50V 1uF polarized capacitor (or as they're called in japan, "condenser") at a small electronics store after work today.  Extra bonus pickup, a spare Famicom for only 1000 yen!  It had the plastic expansion cover, which mine was missing, as well as two nice new-feeling controllers and the power/reset button stickers.  So I gutted that thing and transferred all the new parts to my modded system.

Clipped the white wire from the sound pad, and soldered the capacitor to that wire, jumped a red wire (from my leftover arcade stick modding supplies), and tacked it onto that third pin.  Everything works great and fits in there just right... so nice to hear that extra sound channel in all its glory.

Couldn't have done it without your patient guidance--I had more or less figured it'd be an impossible project but it ended up being really manageable.

Here's a picture, packed with "elegance":



Thanks again! 
Post Merge: July 07, 2011, 05:46:08 pm
Also, Xious, are the reproduction disks listed in your catalog for sale?  Despite the presence of a view cart/checkout section, I cannot find prices or ordering information anywhere.  I wouldn't mind buying something off you to thank you for your help!

[Xious]

I don't have an on-line ordering system, or at least, the one that is up there is only half-functional, so I disabled most of it. I handle all orders by phone or e-mail, and yes, you can order reproduction disks.

Good to see you've finished this. For the record, they're also called condensers in Europe and the Americas, but here the term 'capacitor' is the preferred.