7800 power supply circuit mobo side

vandymachine · October 12, 2014

Does anyone here have a schematic of the 7800's power supply circuit? I am learning as I go as to modding game consoles and accessories. I was sucessful at modding an original NES pad to work with the 7800. It worked on the first try!

It all started while attempting to install the Longhorn Engineering board from Electronic Sentimentalities. Everything tested ok on the composite side before I attempted to mount the jacks. I also tried to hook the Tia 9 wire to the original channel selector jack. This is where things started to go off the rails.

I screwed up when drilling the holes for the s video & composite jacks. I drilled them up too high. Now they hit the side of the motherboard when it is attempted to be reinstalled. I attempted to fix this issue by cutting down the side of the board and relocating part of the power supply circuit on the motherboard.It now only shows a pattern on the screen with an annoying sound or plays perfectly. You have to reset the cart & restart the system multiple times to get it to work. Another issue is when the systems wall wart is plugged in, the power light is on dimly. When the power is turned on to the system the light is brighter.

How can this system play perfectly one time then the next time not work at all? I guess everyone has heard the "you can't make an omelette without breaking a few eggs". It's not so funny when you have a perfectly good game console and blow it up by experimenting. I will try to post pictures tomorrow as I get time.