C67 SNES Capacitor Missing

[alec006]

So after reading about all the SNES variants and wanting to know what video encoder chip I have, I opened up my SNES. I always loved knowing that I had one of the first models of the SNES. SHVC-CPU-01 Rev 5 with a S-ENC 9231 M51 F video encoder chip.Then I realized something was missing. The C67 capacitor spot is blank.

http://i103.photobucket.com/albums/m137/darkknux_2006/SNESR5.jpg

Now I looked it up and found a SHVC-CPU-01 Rev 2 board on Wikipedia and turns out it has a capacitor.

http://upload.wikimedia.org/wikipedia/commons/a/af/SHVC-CPU-01_F_01.jpg

Now my SNES works perfectly except with Super Mario Kart which for some reason doesn't play properly on it. My question is, what is the C67 capacitor used for?

[FABombjoy]

Presumably for power supply filtering. It's not uncommon for that spot to be blank.

[alec006]

Presumably for power supply filtering. It's not uncommon for that spot to be blank.

Make sense, I actually found a SNES schematic and it shows that that particular capacitor is on the power switch circuit. Thanks!

[cynicalhat]

is it me or does your fuse look all burnt?

[cynicalhat]

http://www.videogameobsession.com/videogame/snes_hardware/snes_hardware.html

this site has a picture of the capacitor you are looking for

[alec006]

is it me or does your fuse look all burnt?

I think it's just the picture because I did check that fuse when I was looking at all the chips. System wouldn't power on without the fuse right?


http://www.videogameobsession.com/videogame/snes_hardware/snes_hardware.html

this site has a picture of the capacitor you are looking for

Thanks for the info ^^

[cynicalhat]

I think it's just the picture because I did check that fuse when I was looking at all the chips. System wouldn't power on without the fuse right?



Thanks for the info ^^

it just looks like the solder joints are looking crispy around it is all.

[cynicalhat]

i just pulled apart a 1990 SHVC-CPU-01 SNES. And this one has the capacitor. On the cap it reads "25v 1000uF"

(edited to put quote marks)

[bigbacon]

I am bumping this ancient thread because I have a question about this.

If my SNES doesn't have C67 populated and I populate it...what happens? I am going to recap my snes to see if it clears up an issue I am having.

[FABombjoy]

It will add one more layer of power supply stiffening.

There is already a large cap in the OEM power supply but Nintendo removed them from all non-SHVC NTSC boards for cost reduction. Not strictly necessary but I always add them.

They are present on PAL PCBs because the voltage rectifier stage is inside the SNES and not inside the wall adapter. I believe this was done to provide 12V to pin 8 for auto switching.

They may help NTSC units if using 3rd party supplies (like the 2-in-1) but I haven't tried. Most 3rd party SNES power supplies are junk and should be avoided at all cost.

[bigbacon]

my is an SHCV model and doesn't have it which is why I asked. So no harm done if I used the one in the kit i got.

[Niku-Sama]

Nope probably either no change or little bit of a noise filtering effect with that big of a cap.

If it's any consolation i haven't opened any snes systems that had the cap

[bigbacon]

So I got another SHCV board and it has the cap.

So now i have another issue. my original SNES board had some kind of memory issue. this board fixed that but it acts strangely on different TVs.

CRT: Svideo is black and white, composite works but at some point i get weird color flashes all over the place.
LCD: Svideo and composite both pulse. like the screen shrinks and expands a bit endlessly
Plasma: Svideo and composite both work fine with no color artifacts.

All three of my tvs work fine with every other system so I know it isn't the TVs. Another dying board or weird power supply? I don't see any bad/leaking caps on the new board. I have another SNES on the way as well. Just hoping one of them works and/or I can repair this one so I can have a backup or sell it.

[Niku-Sama]

You got me on that video issue.... Huh

[RP2A03]

Could it be a grounding problem or an issue somewhere in the chroma signal path?


EDIT: I just realized that the composite signal comes directly from the video encoder instead of being combined after the encoder. Check the ground and the pins on the multi out then reflow the video encoder.

[bigbacon]

I will add. wiggling the video cable or the video port doesn't change the issue so I don't think it is the cable or the connector.

[FABombjoy]

Total guess here, but misadjusted system frequency?

The RGB encoder is fed a color clock signal from the PPU that is derived from the system clock. That little trimmer cap TC1 is part of the system clock. If the chroma carrier has drifted enough some TVs may not be able to lock on to the signal.

I've never tried adjusting TC1 but if you're willing to see what happens please post your results :D

[bigbacon]

i would think it would be a consistent screw up on those TVs then and not totally random. I mean it could work fine on my CRT for some random amount of time, they go crazy, then get better, then go crazy again.

[FABombjoy]

That's why I wonder if it isn't right on the very edge of adjustment, or if maybe the clock feed into the RGB chip isn't funky. Nintendo loved to cost reduce and would have eliminated TC1 if they could have, which they did in some later SNES revisions. Even heat / humidity can affect a circuit just a teeeny bit.

If I had it here I'd put a frequency counter on the system clock circuit & the RGB chip and see where things are at. Since the PPU provides the clock this could possibly another symptom of PPU failure as well. If the chroma frequency is off then color will be inconsistent, and if you feed an LCD a poorly clocked signal then I would expect the ADC stage to have issues. Your plasma may just be more tolerant of carrier drift. These are just guesses tho.

Come to think of it, I may have a SNES here with a "plays in black & white" stickynote on it. I'll see if I can find some time to poke at it.