Super Famicom video problem

[Demiurgo]

Hi all!

I have a problem with a Super Famicom... the screen is totally black! I read about similar failures,but in my case, audio is working and when using RF, image is totally fine... but using AV cable I got no image.

I used different cartridges and cables, and even I tried to take signal directly from pin 9, and replacing the capacitors near the Multi out port, to no avail. Always the same problem, black screen, with sound, and  using RF cable, all works fine.

Any idea about what to check or try? 

Thanks!

[Demiurgo]

 

[famifan]

hi, do you have access to the oscilloscope? it could shed more light on the issues experienced by you.

anyway, it seems that your console is having issues with the port. Let me explain a bit more, since RF needs both A & V signals for operating, that effectively means that console is capable of producing both A & V signals of required level.

I would recommend to inspect the AV part of the board (sorry, i'm not familiar with SuperFami, i hope it does have this kind of board).  Just check how the video signal is passing. I believe there're some obstacles could on its way. It could be a short circuit and/or broken traces (no connectivity) and/or failed electrical components. Simple multimeter may help you, however, the oscilloscope is way more preffered for this kind of tasks.

[Demiurgo]

Hi, famifan. Yes, I have an oscilloscope. I am not sure the problem is in the port, because I tried to take the signal from the pin in the board and no video neither. I will try to trace it back, but I see no cut trace at all. Obviusly the console is working, or no video neither by RF. Also, sound works by the Multi out  port. Any advice about what to check?

Thanks!

[famifan]

the same video signal goes to RF modulator and to AV-port too. You can trace it back to the point where it starts to split into RF and AV parts, of course, with the help of oscilloscope.

happen to have any detailed pics of the AV board from the both sides? perhaps i can show you some test points on the pics.

[Demiurgo]

FIXED! 

I traced back the video trace on the board from the pin9 on the underside, it went past a SMD capacitor and a SMD resistor, then to a pass thru hole to the upper side of the board, to another capacitor, and there was the problem: the hole.

The trace was OK on both sides, but acid from old capacitors (now replaced) damaged the hole, so there was no connection for the trace on both sides of the board.

I just made the hole a bit bigger, inserted an insulated wire and soldered both sides to the SMD resistor and the new capacitor, and... it works! 

[famifan]

awesome news! well done! 

so, a damaged via was the root cause of the issue.

[Demiurgo]

Thanks! 

Acid from capacitors can do more damage in a tiny space where it can accumulate...