Max DC voltage input for the Atari 7800

[unebonnevie]

Hi,

 

I just got an Atari 7800 from eBay, and, as usual, it does not come with the power adapter, which has an insane strange connector. So, I am going to do a power mod. I have a 9V DC and 1A output adapter, as stated on the power adapter's label. When I measure the voltage output, it's always 12.47V. Pretty strange. So, I was looking at the Atari 7800's schematic but can't find if it has some sort of voltage regulator (like the 7805 voltage regulator) to ensure 5V is what all the chips on the motherboard get, even with 9-12V input.

 

So, is 12V to high, even the adapter says it has a 9V output. By the way, why does the power adapter has higher output than it claims?

 

Thanks!

[CPUWIZ]

It does have a 7805, it is behind the cart slot, mounted to a huge heat sink.

[Shawn]

You can use up to a 15v power supply no problem. Watch the amperage though, too high on that and it's gonna pop.

[desiv]

Not very familiar with electronics, but I didn't think you could have "too much" amperage per se.

I thought that the device pulls what it needs.

So as long as you have "enough", having too much available shouldn't be a problem.

The PSU doesn't push all those AMPs to the device????

 

desiv

[BigO]

On a typical non-regulated supply, the unloaded voltage will be significantly higher than the rated voltage output. 12-13 is nothing to be scared of for a 9V rated supply. It'll drop right down when it sees a load.

The board itself actually operates off of 5 volts. The aforementioned regulator in the console takes care of that. As I recall, those regulators will typically handle input voltages over 25 volts with no problem.

[Osgeld]

25 volts yes with little to no load cause its dropping 20 volts as pure heat

 

12 volts is fine

 

you cant have too much current from the system side of things it will only take what it wants, from the power supply side of things if its unregulated and your not using 60-70% of its current capacity, the loaded voltage wont fall into line, which goes back to point 1, more voltage in, the more the regulator has to burn off as heat