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PostPosted: Sun May 28, 2017 9:21 am 
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Joined: Sun May 28, 2017 9:16 am
Posts: 2
I recently got hold of my old SNES from my childhood. It has been lying in an attic for the last ~20 years. When powering it up it does have some issues.

I own 7 games (I have a second working console that plays all of these fine, so I know the games are good). The following games work fine:
B.O.B
Donkey Kong 1
Donkey Kong 2

The following give a black screen and no audio:
Star Fox
Donkey Kong 3
Yoshis Island

The last one is Super Mario World, which only displays a white screen and only plays the "ding" sound in the very beginning of the game (when the Nintendo logo is suppose to show).

For the games that do work, I noticed there is a tiny bit of audio crackle just before the image is shown on screen. After that the audio is fine. When testing on my working SNES this audio crackle does not occur.

When opening the console, I noticed that capacitors C59 and C60 had some black gunk running just below them, so I removed them, cleaned up and replaced them with new caps. Also C61 seemed a bit dodgy, so I decided to remove that as well. Upon removing it, I saw it had leaked, so I cleaned up by using vinegar (to neutralize) and isoprop alcohol afterwards - before soldering in the new cap.
This procedure made no difference in terms of making the games start.

I then properly cleaned the cartridge connector by the isoprop-cloth-creditcard method, but without any luck.

After that I tried the cartridge connector from my working console, same result. When trying the cartridge connector from my non-working console in the working one it boots fine, so I can rule out that part as the culprit.

I tried the method of touching the chips and caps while the system is on for a while to check for hot (and potentially defective) components, but the all feel room temperature to the touch.

After reading online for a while it seems that the chips on the board can go bad. But if one (or more) of the chips on the board is done for, wouldn't no games work at all?

I've done a visual inspection of the board, to check for bulging caps, corrosion etc. The only thing I can think of next is to replace the remaining capacitors - even though the look fine.

Any other suggestions on how to proceed?

Thanks!


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PostPosted: Sun May 28, 2017 11:04 am 
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Joined: Tue Oct 06, 2015 10:16 am
Posts: 558
Your non-working games all use expansion chips, no? That means they draw more current, and power supplies can go bad with age. Check if your power supply still gives the right voltage and amps.


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PostPosted: Sun May 28, 2017 11:13 am 
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Joined: Sun May 28, 2017 9:16 am
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Thanks. I suppose - but all games play fine on my working SNES with the same power supply (I only have one).


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PostPosted: Sun May 28, 2017 11:56 am 
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Joined: Sat Apr 25, 2015 1:47 pm
Posts: 329
Location: FL
calima wrote:
Your non-working games all use expansion chips, no?


SMW and DKC3 don't.


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PostPosted: Sun May 28, 2017 1:08 pm 
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Joined: Tue Mar 01, 2016 8:22 pm
Posts: 21
I'd replace the remaining caps. My guess is greater power draw from the special chip games is putting more load on the main filter cap (the 1000uF one), and if that's bad, then the system could dip below 5v, causing many games to either glitch out or not run at all.

Can we get some pictures?

I'd also replace the 7805 with a modern 1.5A or 2A one that has thermal shutdown protection and overcurrent protection. Not saying the existing one is bad, but it's good practice. I replace all of the 7805s in all of my consoles with the 78S05 myself, just so I can have massive headroom and less heat.

Also, if you have an oscilloscope, measure the 5v output from the 7805 with the trouble games and make sure it's at a stable 5v. If not, get a multimeter and test it to make sure it never dips below 5v (give or take ~0.05v).


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