Famiclone coolbaby rs-37 not saving games

Started by infamouscom, November 10, 2021, 04:59:31 am

Previous topic - Next topic

infamouscom

Hi. Recently I got a chinese famiclone. It has been great to get the nostalgia from the 90's. With it, I got a multicartridge which is a 154 in one. It has a battery to save progress in a few games like Zelda, for example. But I never got to make it work.

I've already checked with a multimeter and the battery is full. When I press reset the game is still there, saved and I can continue my process. But if I turn down the system, it erases everything. I don't know if this is a problem with the cartridge or the famiclone, honestly. I also find it weird that the famiclone says it needs a 9v power plug and it came with a 6v one. But on a close look to the psu it looks it does work with a 5v input (feel free to correct me, I'm no expert in these matters)...

Sadly, for the moment, I have no more cartridges with battery to test. But maybe this is a know problem and you can clarify to me if this just normal with this type of famiclones. I'm uploading some photos of everything.

Thanks.

infamouscom

A few more photos, including the multicartridge board.

P

If a game doesn't save it sounds like a problem with the cartridge, but I don't know for sure. Retaining data over a reset is normal because the power isn't cut when you push RESET.

The main board itself (including the cartridge) uses 5 V but to get a stable 5 V supply it uses a voltage regulator (labeled 7805 on the board, three-legged black thing) as the AC-adapter can't provide a stable voltage supply alone. The 7805 voltage regulator requires a minimum of 7 V to work correctly though, so a 6 V AC-adapter sounds too stingy to me. Normally a 9 or 10 V AC-adapter is used with these systems.

emerson

November 13, 2021, 11:52:33 am #3 Last Edit: November 13, 2021, 11:59:14 am by emerson
6VAC when rectified to DC would be (6/0.707 = ~8.5VDC) so that should be sufficient. However, the power supply in the image is 6VDC which is odd...

In regards to the battery voltage, keep in mind that the SRAM does not see the direct battery voltage but rather the battery voltage minus the forward voltage drop of a diode, or about 0.7 volts. The best way to measure if the battery voltage is suitable is to measure across the power supply pins of the SRAM chip itself.

Typically there is an RC network on the SRAM VCC circuit so the voltage transition from console supply to battery supply is smooth. If memory serves these are around 10k and 22uf respectively. I don't see these on the cartridge pcb images you posted. An unstable voltage transition will erase the SRAM.

A full 2032 coin cell measures about 3.3 volts. Seeing that it's socketed, have you tried installing a brand new one?

infamouscom

Hey guys, sorry for the late answer.

So, I have some news. Turns out that the battery was faulty. It is strange because I've checked many times and the multimeter always indicated around 3v of charge. I bought some new ones and it is working good now. It saves progress. :upsetroll:

Also. Thank you very much for the answers. Both of witch are so complete and explanatory. Looks like this is a good place to learn something, for sure. I like to open things, to see what's inside the case. I've been working and maintaining my consoles (not clone systems) for the last years. Changing some capacitors and stuff like that. Never really dealt with power supplies, so your information about that is something I enjoy knowing about.

Thanks