SNES Mainboard Repair No Sound [Serial: UP17388130]

Another weekend, another SNES! This one has no sound but has picture perfect.
I'd ordered some capacitors to replace and did so (well... a friend did while I recapped unit UP15971140).
We noticed a few of the caps had leaked about the board, however the issue still remained - no sound!
So I thought about poking around to get some sound directly from one of the chips.

However I noticed in one of my earlier photos in gallery for the unit here, that there is a hole in my bucket, my bucket... Maybe that song should be redone and the word bucket replaced with S-MIX microchip. Poor S-MIX at U10 on this 1CHIP has been blown open apparently!



Full resolution photo here.

Anyone here got a good understanding of SNES audio circuits? I take it the S-MIX chip would usually mix two lots of audio together and mince it out through the multi-out connector. Is it possible to simply take the audio from another source before it reaches that chip? I've seen U6 - the 6379A mentioned a fair bit. Any thoughts on how I can work around this little issue?

Edit: Possible solution here!

 

You could try an S/PDIF mod:

http://www.alpha-ii.com/Info/snes-spdif.html

The whole APU circuit was made into a custom chip on these later units - I'm not too sure on what the S-MIX chip replaces. Anyone?

How come you're not using surface mount capacitors? Make sure you're using quality low ESR capacitors in the audio stages for the best sound quality, of course!

 

As much as I do enjoy a good Sega console and their many revisions, I was very happy to find that Nintendo revised almost as much as Sega did!
I've been meaning to start a WTB thread for an S-MIX from a dead board.
And don't worry I always use low ESR caps!

I tend to go for radial where I can, it's a lot easier to see when a capacitor is leaking. The SMDs hide it a little too well.
Especially given not all of these units will be out and about over the next 10-15 years probably, I'll enjoy checking in on them every so often.
I do understand that SMD electrolytic caps are just as good these days, but I like my caps with legs.
Long, long legs...

 

I prefer it to look as original as possible. Radials just look messy - especially if you use super large blobs of solder!

You should never rely on just a visual inspection to determine if a capacitor is faulty - even a radial electrolytic can look fine when it's gone.

 

The S-MIX chip has exploded, Retro. Look at that white bubble it looks like a dead volcano.

The chip blew like that because someone inverted the polarity at the power plug.

Edit: I just noticed (looking at the picasa pictures) that it's a SNSP unit so it takes AC as input. Sadly blowing the S-MIX chip on NTSC units is quite common. :very_drunk:

Perhaps the S-MIX could be replaced with a generic amplifier circuit ?

 

I know it has. That's why he asked if there's a way to bypass the S-MIX, and I suggested an S/PDIF mod, which doesn't need S-MIX.

I'm still none the wiser as to what S-MIX actually does, as I don't have a circuit diagram for a later SNES. I thought the amplifier was always within the APU.

 

Sorry retro, I meant RetroJunkie

 

Oh don't worry, I'm proactively replacing caps as I go along my merry way.
One of the other reasons I don't do SMD electrolytic caps is that I don't have the tools.
What would be the best tool to remove and resolder these on? Some sort of tweezer soldering iron?

Yep hole in the S-MIX, there's a hole in my S-MIX! I've found that this unit runs with DC with polarity either way around.
It does seem that the US SNES units do not like AC at all though.
I'd test this one with AC, but from what I've read it should work, well the tip off the original adapter is missing anyway...

Huh? I know it's blown up! That's what I said in the first post! :wink-new:

 

Hot air. Or you can usually do it with a soldering iron and a steady hand.

http://www.youtube.com/watch?v=5Ts6lPkYDsU

And no, that's not my video!

See?! I KNEW all these retro clones would get confusing sooner or later!

 

People can call me McRetro if they will but I will have a strange accent from that point on! :congratulatory:

Hot air looks like a great idea. Too bad my cheapy heat gun decided to catch fire after the fan stopped working... :dejection:
What other ways would you use if you didn't have access to a hot air gun? Metal fatigue them off and solder like in the video?

What are the surface mount caps casing size range, similar to that of tantalums?
The SNESes have two sizes from memory, the 2.2uF and all the others.
Maybe on the next round I'll give surface mount caps a try. Who knows maybe I'll fall in love with them!

 

You're an Aussie... you already have a strange accent!

Get a clone hot air station off eBay - they must be cheap in your neck of the woods. They're around £40 for the cheaper models here, I believe. Other than that, you can still either pull them off (watch the tracks) or heat the legs on the sides, then do as he did in the video with a soldering iron.

There are a few sizes IIRC... get a micrometer off eBay and use a good supplier who lists dimensions in a table, like Farnell.

 

Oh come on it's not that bad. I consider it evolution! :biggrin-new:

I'm trying to get an other over $45 now to get free shipping. So far all I have is a bunch of caps and a microchip.
I know there's more I need! Too bad they don't have S-MIX chips by the dozen.

 

Evolution from aborigines and our overflow of criminal scum? I guess!

It'd be cheaper to pay for the shipping! Find a company that has a small order charge of a few dollars. Or get yourself a hot air kit

 

LOL we were free settlers we were, we loved a challenge and thought why not.
Why free land from the Commonwealth was enough to get us moving! :biggrin-new:

Farnell / Element 14 is fine for me. At least I know the components are legit, unlike say... eBay!

 

http://www.youtube.com/watch?v=f4hSMwLOI3Y

 

I will take some snaps of my nice 1 chip pal unit the only pal 1 chip i ever had the last one was a ntsc usa unit.

 

I'll check the pin outs on my working 1CHIP, but U10 looks awfully familiar on the non-1CHIP board I have.
Which is good, because I may have a spare one of these that has a terminal issue.
Does anyone well versed in SNES know if the S-MIX chip is a LM324 in disguise?

 

I have yet to find anyone who can tell me what that damn S-MIX is! lol

 

Well... I'm willing to sacrifice a 20 cent LM324 to try and get one step closer to the answer.
Provided the pinout has voltages in the correct spots that is! :smile-new:

 

The pinout is different, that is certain ...