Dangers of opening SNES (old-style)

blargg · Post by **blargg** » Wed Apr 30, 2008 5:33 am

I'm so angry right now. I had opened my old-style SNES to make a mod, and apparently when I was putting it back together I killed one of the PPUs. So now games are missing a couple of graphic layers. I am pretty sure it was the damn power switch on wires that did this. The 10V power input goes through a large filter capacitor before the power switch, so even when the adaptor is not even connected, that capacitor is charged and if the live terminal of the power switch touches the circuit board, it'll send a high-current, high-voltage pulse through whatever it contacts. A while back the thing had shorted to ground with the power supply connected, blowing out one of the protection diodes, so I should have known to be more careful.

My advice
1. Before you open the case, unplug the power adaptor from the SNES, and then turn the power switch on momentarily. This discharges the capacitor, and the power light might flash. The cartridge can be out when doing this (so the momentary power doesn't mess up your battery saves).

2. If you'll be running the system out of the case, be sure the power switch is well away from the circuit board before plugging the power adaptor back into the SNES.

3. Finally, before re-assembling things, do step 1 again.

EDIT: I did some testing and it seems it just killed BG0. BG1-3 work. VRAM $0000-$FFFF seemed to work fine when I put tilemaps and tile data there.

EDIT: improved advice to be more thorough.

blackmyst · Post by **blackmyst** » Wed Apr 30, 2008 2:38 pm

My condolences.

Johan_H · Post by **Johan_H** » Wed Apr 30, 2008 3:15 pm

Yikes, good to know, I'm actually opening a SNES myself in a just few minutes.

Also:

blargg wrote:I'm so angry right now.

creaothceann · Post by **creaothceann** » Wed Apr 30, 2008 3:42 pm

Post by **badinsults** » Wed Apr 30, 2008 8:13 pm

Yeah, when working with any sort of electronics, those are all good points. Always making sure that the thing is unplugged and discharged is also a good way to prevent painful shocks.

Gil_Hamilton · Post by **Gil_Hamilton** » Wed Apr 30, 2008 9:48 pm

RIP SNES

Blasingame · Post by **Blasingame** » Thu May 01, 2008 1:20 am

Never thought about modding my SNES, where is a good site for finding different mods for it?

adventure_of_link · Post by **adventure_of_link** » Thu May 01, 2008 2:10 am

for one, there's the 50/60hz switch for the first model SNES, and I even know how (but unfortunately never tested) to make it run off batteries

blargg · Post by **blargg** » Tue Aug 05, 2008 11:29 pm

I pulled my SNES out of a box, after having been there since my first post. I was opening it up and remember this, so I turned the power switch on to discharge the capacitor and the power LED turned on for a moment. It was still charged after all that time!

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Dangers of opening SNES (old-style)

Dangers of opening SNES (old-style)

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