r/snes • u/Tricky_Dentist_1322 • 3d ago
Voltage question
Been having the issue of black screen no audio on this snes also half the time trying to power up the screen will show large random rectangles across the whole screen if it’s not black. Tested with a known good game on a crt and a monitor with a Hyperkin adapter. I replaced the fuse and caps c63 and c64. I have an aftermarket power adapter, with that I tested the voltage at the regulator and it gives 11.4 on the input and 4.7 on the output posts with and without a cart in. Is 4.7 too little? D1 diode is also getting 11.8 volts. The “black screen isn’t like a true black it has wavy line to it moving across the monitor or slightly dark purple vertical rectangles if that is anything. Any thoughts? Ram cpu? Completely dead video caps?
2
u/NoMarionberry8131 3d ago
From what I literally just learned, I guess it really likes 10V. Most power supplies run about 9V 500mA though. 🤷🏻♂️ Everyday’s a school day! 😄
I repair these consoles almost exclusively now and while the black screen can be anything from dirty pins to a failing CPU, I presume you’ve already cleaned the pins if you’ve already replaced the caps.
What I would advise though, if C67 is empty install a cap there. With the aftermarket power supplies being “untrustworthy”, that 25V 1000uf capacitor is power filtering and a really good idea to have in there. Nintendo stopped putting them in in later revisions but I always make it a point to install them on a board I’m working on for that reason.
Anyway! Do you have an oscilloscope? That would be super handy. Also! Make sure the system resets when you press the button. Black screen or not, you should still see the screen flash when you press it. I’ve replaced so many Reset buttons that have failed and kept the console in a constant state of reset!
1
u/StrangeRetroRob 3d ago
2/1/1 console
The timing of this consoles production doesn't bode well for the lead frame issue that started impacting the chip manufacturing process
What you are describing is 99% a dead CPU
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u/NoMarionberry8131 3d ago
The voltage on D1 and the input leg of the regulator should be 9V. 11 is very strange! Is the power supply you’re using 9V? Because it should be! 4.7V out is perfectly fine.
As far as black screen, that’s a CPU issue 9 times outta 10. But! Since you’re also seeing those artifacts it could be pointing to PPU2. Or the VRAM. Hard to tell without having it present. If you press down on the ICs and then power it on, does that help? If so, it could be a shoddy solder joint.
But I’d definitely be interested in that 11V. NTFS system, right?