Stories from the -: ITC :-

I never really understood why GCC designed the 7800 with this type of power-up system. Having the console always powered and using the flip-flop to just start sending power to the rest of the system. Maybe there is something I'm missing, but when I designed my portable 7800, I changed the circuit to just have a standard power switch which turned the system on/off, without this transistor or flip-flop. Don't want to always be discharging the lipo battery.

Likely just a hold over from the 5200 since it works on the exact same setup? Only in the case of the 5200, you have 2x as much to deal with since it has twin VRs switched on by a pair of those 210s. So you can get a 5200 that looks to power on but still dead because only one of the two VRs comes up due to a faulty 210 that should be driving the power over to it.

 

That said, I've only had one 5200 where I had to replace that 210 while I've done this like 3 times over the years in various 7800s. Then again, I've serviced a LOT more 78s than 52s so I'm sure the stats are the same between them.

 

You know in thinking about this, I'm sure they did this because of how they handle the reset to the system? They actually reset the 5200 and 7800 using the reset pin from the 4013 IC to quickly cycle the power off/on this way.

 

I only really learned about this after getting my BackBit Pro cartridge because for full use of the cartridge, you have to attach a reset wire off the 4013 ICs back to the BBpro cartridge so the button on the cartridge can control the soft reset function and work as intended.

 

I had to create a different reset circuit for the portable, which allowed me to not implement any of the original 7800 power-up/reset design.