Left audio/ Right audio Question

[Cojiro]

For some reason the right audio from my n64 is not working. I have tried different things, finding alternate spots to wire to, I have even cut a section from another n64 and wired through that, and nothing. I don't care about not having stereo, but I CERTAINLY don't want only 1/2 of mono. There are two pins on the cartridge slot that are for signal right and left audio, coming directly from the game. Whatever circuitry that these have to go through on the n64 to produce a readable signal for speakers is working on the left audio, but not the right.

THE QUESTION: Would it be okay to bridge these two pins, putting both signals through the left audio part of the board, would it be safe?
And if not, do I have any other options?
Thanks

 

[ToastBucket]

For some reason the right audio from my n64 is not working. I have tried different things, finding alternate spots to wire to, I have even cut a section from another n64 and wired through that, and nothing. I don't care about not having stereo, but I CERTAINLY don't want only 1/2 of mono. There are two pins on the cartridge slot that are for signal right and left audio, coming directly from the game. Whatever circuitry that these have to go through on the n64 to produce a readable signal for speakers is working on the left audio, but not the right.

THE QUESTION: Would it be okay to bridge these two pins, putting both signals through the left audio part of the board, would it be safe?
And if not, do I have any other options?
Thanks

In theory it would work, but whether it's safe is a different issue. You will basically be combining two wavelengths, something that generally requires a circuit for safety (mixing amp). You could possibly damage the TV or audio amp you plug it into to play, depending on whether it has protection for this built into it.

You've probably got a goofed up onboard audio amp. Just take one off of a dead board or see if someone will send you one in an envelope. The audio amp is U2:

 

[Cojiro]

So it could be goofed up in a way that left audio would still be functioning fine?
(And okay, I disconnected the left audio speaker and leaned really close to right, and heard a very faint audio, you could tell it was from the game though, not just white noise. I don't know if this is a symptom of anything)

 

[ToastBucket]

So it could be goofed up in a way that left audio would still be functioning fine?
(And okay, I disconnected the left audio speaker and leaned really close to right, and heard a very faint audio, you could tell it was from the game though, not just white noise. I don't know if this is a symptom of anything)

If this is in a portable, could be a bad speaker. Try wiring up a new cone first.

 

[Cojiro]

nah, one of the first things i tried.

 

[ShockSlayer]

IIRC those two contacts on the cart slot are NC anyways. Could be the amp, you could've accidentally popped off a cap or resistor in the A/V out area. Have you tried wiring sound directly to the amp?

SS

 

[Cojiro]

no, has that been done before, with success? (is there a pin out somewhere)

 

[mymixed]

I've done it, works fine. My amp for the speaker was an lm386, but there should be no problem mixing channels. It really shouldn't damage anything.

Story:
I had one set of speakers, but had two computers. So I got a headphone splitter from Ratshack and plugged the splitter into the speaker sub-woofer thing, and the other end of the splitter into the computers. It worked fine and I could play sound on both computers at the same time. Now this isn't mixing Left and Right audio, but it is mixing audio.

So yah, it should work. If not, post what you find .

- mymixed

P.S. You should probably just replace the audio amp. If it doesn't work, your board still works! It's just the audio thats not working.

 

[Cojiro]

So yah, it should work. If not, post what you find .

Ugh that makes me feel uneasy about it. You are referring to my original idea, right? I have another n64, I will sacrafice it to test, if that's what it comes to. I've put a decent amount of work into this board already (trimming, rewiring, glued on heatsinks, cart relocation), so I'll probably hold off on things that only might not damage it for now.

I am interested to find this U2 pinout. I must be confused as to why the board needs an audio amp and speakers need an audio amp, I'm not the most familiar with this stuff.

 

[mymixed]

Well you can use the old board for another portable, or sell it. I'll look into the u2 ic. Then I'll post a pinout.

- mymixed

 

[ToastBucket]

I had one set of speakers, but had two computers. So I got a headphone splitter from Ratshack and plugged the splitter into the speaker sub-woofer thing, and the other end of the splitter into the computers. It worked fine and I could play sound on both computers at the same time. Now this isn't mixing Left and Right audio, but it is mixing audio.

It works 9 times out of 10. Most amps have circuits to protect from that, like yours obviously did. 99.9999999% of the people on this planet do not understand waveforms or how amplifcation works. I know it will work, but I don't know if the amp he was plugging it into could handle it or not. I didn't want to tell him that it was fine for him to do something, and then have it damage his TV's amp (I didn't know it was for a portable at first.)

But yeah, a cap could have popped off, or may be dead. First I'd try wiring directly to the amp (pinout is in Beta's I Spilled The Beans thread I think). If that doesn't work, I'd replace the cap for Right Audio. If none of that works, I'd replace the entire amp chip.

 

[Cojiro]

I'm using the psone screen (and speakers), if that helps.

In that thread, it says that audio can be pulled from the U1 chip, and that you don't need the U2 chip. Also, excuse my ignorance, but it says you need a capacitor for filtering, what kind?

The N64 can be be trimmed a lot.

http://i.imgur.com/Y7RUY.jpg

The U2 chip is just an audio amp, don't need that.
The audio amp and the 7805 that drives the U1 chip are the only things on the 12v line. The U1 will happily take ~3.7v, so you can easily run the N64 off of a single lithium ion cell.

Audio and video can be pulled off of the U1 chip, here is the pinout. You need a capacitor on each of the data lines for filtering.

Rev 8/9

Pin 17 R Audio
Pin 20 L Audio
Pin 27 Composite Video
Pin 28 5v


NOW GET TRIMMING!

Thanks to all.

 

[mymixed]

Ok toast, I see. Probably the older amp ic's don't have protection. He could run it through an lm386 and then put it in his tv, but thats 3 audio amps so he should probably just use his new board . Luke: If you ever work on that other board again, tell us what you find.

- mymixed

 

[Cojiro]

Oh I plan on using this board. The new board I was only going to use to test on if it came down to hunches and guesses, because I'm more willing to risk damages to it then this current one that I'm working on. It is for a portable, and I am using the psone screen, not a home tv. I'm not much of a worklog person, but this one is completely wired, just trying to get this one problem fixed before I case it. I've got pretty high hopes for this U1 chip (what capacitor do I use, a 100uf 35v?), so we'll see what happens when I get home.

If I do get this working, though, I would like to test my pin-bridging idea on my spare board, to see if it works, and then I will post my findings.

 

[ToastBucket]

The PS1 screen also amplifies, so the problem could be there.

 

[Cojiro]

and it looks as though my n64 has stereo sound once more.
thanks guys <3