N64 voltage question

MM007 · Post by **MM007** » Wed Jul 27, 2005 3:23 pm

I am aware that the N64 has 3.3V and 7.2V (12V) lines with a common ground, but am wondering something.

Would it be possible to find where the grounds are tied together, seperate them into a 3.3V's GND and the 7.2V's GND, and tie together the two in series, 3.3V first and the 7.2V after that? (using the 7.2V first would burn off all the voltage meant for the 3.3V because of the 7805) That way, 10.5 minimum would be required, and a single 12V battery could power the thing more efficiently.

I want to know because then I could use my 12V screen with the N64, (beter quality than my third party PSOne screen) and squeeze out as much efficiency as possible for low cost.

Can this be done? Does anyone know what points on the board the two grounds are tied together?

usbcd36 · Post by **usbcd36** » Wed Jul 27, 2005 6:59 pm

I don't think so, but the grounds might not be completely connected (just inside the power adapter) and you might be able to manage, but why don't you just use switching regulators to get 3.3v and 5v (bypass the 7805) instead?

MM007 · Post by **MM007** » Wed Jul 27, 2005 7:41 pm

Maybe...how expensive is that?

*o* · Post by ***o*** » Thu Jul 28, 2005 12:26 am

not too much...depends what brand etc.

usbcd36 · Post by **usbcd36** » Thu Jul 28, 2005 11:44 am

Your first idea might not be so good after all because some of the batteries will drain very quickly (the 3.3v line is 2.7A) and the others will drain more slowly (the 12v line is only 800mA). Just use a regulator and tantalum capacitors to get the 7.2v down to 3.3v and send the 7.2v into the N64's 7805. The screen will have to draw from whatever is left. I suggest a PSOne screen because the 7.2v battery actually outputs about 9v and the PSOne screen can still take that.

Post by **Gamelver** » Thu Jul 28, 2005 4:27 pm

actually, the 3.3V line ranges from 1.2A to 1.5A, and the 12V line is .117A (just powers audio and video

)

*o* · Post by ***o*** » Fri Jul 29, 2005 6:28 am

I checked the 3v it spikes at about 1.5A for a minute or so at start up the goes down to between 1.3A and 1.2A (depends on the game)

usbcd36 · Post by **usbcd36** » Sun Jul 31, 2005 9:50 pm

This is helpful to know, but can the 3.3v regulator/capacitors that are mentioned in one of these threads capable of doing that? Another thing is I've found places that actually sell 3.3v regulators, but they only do 500mA. Is it possible to wire 3 up in parallel to get the required amps?

Post by **Gamelver** » Sun Jul 31, 2005 10:39 pm

probably

...you can do it with 7805s, so I'd assume that it works with other regulators...the current probably won't be divided evenly across the regulators, that's all

(unless there's 1.5A)

usbcd36 · Post by **usbcd36** » Mon Aug 01, 2005 3:18 pm

Ok, ditching my idea of the 3 regulators, how well would a LM317T adjustable (yes, it is 1.5A) work? The range it has includes 3.3v, but how do you wire it?

I have also acquired a few LM723CN adjustable (they can generate Â±2-37v, become a switching regulator, and do all that other crap) regulators. What I need to know is how to wire it to get 1.5A 3.3v switching for the N64. I believe the 12v line is fine with a 7805 (it doesn't use enough power to worry anyway) and the PSone screen is ok unregulated with a 7.2v RC battery from RadioShack, but I really need the 3.3v.

On a side note, I have found a local electronics supplier that sells switching regulators and tact switches. They get their parts from Jim-Pak and sell stuff much more cheaply than RadioShack. They sold me the LM317Ts (4 pack) for about $3.60. The LM723CNs were $4 for 4.