new information about n64 voltage req's

timmeh87 · Post by **timmeh87** » Wed Mar 29, 2006 11:11 am

well, i put the 64 on the power supply this morning, instead of studying for my calc test. i found out some VERY intersting things.

first, i put the screen on wall power and gave the ninteno 64 a full 15 volts. the lines were still there. infact, the lines look exactly the same at 7-15 volts.

i also observed the current draw while using a DC-DC converter. these are idle currents, looking at the "no controller" message in extreme G

7.4v: .9A
10v: .7A
15v: .5A

you can see the DC-DC converter is doing its job. (thats thats the draw for the whole sustem, both voltage inputs)

unfortunately, i couldnt put the screen on the power supply, because it draws too many amps (total 1.5A max on this supply)

so, as an experiment, i decided to see what the dropout voltage of the nintendo 64 is. this is something that has been discussed before, in regards to using 7.2 and 7.4v packs, and when the system would drop out.

what i found was shocking: the system runs properly all the way down to 5.6v! thats with the dc-dc converter. the lines dont get any worse. between 5.6v and 5.3v, the screen gets dim and distorted, and then the system finally drops out at 5.3v. at this voltage its drawing almost 1.5A (idle)

this leads me to a question... what does the 7805 do? i dont have the audio hooked up, so i cant tell you what happened to the sound, but if the 7805 dosent do the sound, then apparently it does nothing at all.

now, my friend suggested i check what votlage the dc-dc is giving out at such a low voltage (its rated for 9). at anywhere from about 6v and up, its giving off 3.24v, which is pretty close enough for me. but as you get into the 5's, the voltage slowly tapers off. i was shocked to find that the system still appeared to run proerly with 2.9v on the 3.3v line! this makes sense from a computer persepective (i mess with the voltage on my P4 all the time), but up until now, common knowledge has been that the 3.3v line needs exactly 3.3v. not anymore.

and since the dc-dc i ordered (the pth08000) is adjustable, im going to set it up to give my 3.3v line something like 3v. why?

1) saves power
2) less heat

its like a pseudo-underclock.

anyways, no new news on the line problem... im hoping the new converter will just make that all go away. or else maybe an inductor will fix it.

daguuy · Post by **daguuy** » Wed Mar 29, 2006 11:43 am

wow, interesting. where would i put an inductor? i have a huge (very biggly huge) one laying around somwhere. that new convertor sounds good, tell us if it works

timmeh87 · Post by **timmeh87** » Wed Mar 29, 2006 11:58 am

i dont know where to put the inductor, but you dont want to be using huge one. pm segasonic about it.

---

apparently, you put it in series with the output. makes sense. but youd want to get something in the uH (or mH?) range.

i looked at the dc-dc with the scope as well. the output looks pretty clean, but it causes massive oscillation of the input line. you might be better off with an inductor there.

XFactor · Post by **XFactor** » Wed Mar 29, 2006 5:12 pm

Timmeh, here's the diagram for the wiring of the new converter. I did it so others can see what we're all talking about here:

<a href="http://img89.imageshack.us/my.php?image ... ram1fs.png" target="_blank"><img src="http://img89.imageshack.us/img89/6956/c ... 1fs.th.png" border="0" alt="" /></a>

I can somewhat understand this diagram in regards to the capacitors, but what perplexes me is how to regulate my output to 3.3v.

That find about how low the current can go is very interesting. It makes me wonder why the N64 suffers so many distortions around 7.4v. Very weird, but sometimes the oddest things can grant you the greatest gains...

daguuy · Post by **daguuy** » Wed Mar 29, 2006 5:19 pm

if you scroll down a bit it shows what resistors you need for which voltage. 3.3v is 1.87k. also you don't need to do anything with the inhibit pin, that's just like a power switch

timmeh87 · Post by **timmeh87** » Wed Mar 29, 2006 5:27 pm

well actually, the line above it means "not". so thats the "not inhibit" pin. vcc is "yes" and gnd is "no", so you want "yes, not inhibit", which means you need to give the pin vcc.

vcc through a resistor, since i dont know if the thing has an internal resistor. never hurts. 10kohm should do

and for the Rset, i reccomend getting a 5k trim pot. you could tune the voltage to as slow as its stable, and then glue it in place so it wont move.

XFactor · Post by **XFactor** » Wed Mar 29, 2006 7:08 pm

does the 1.87Kohm resistor have to be an exact value? could i get by with a 1.8Kohm or 1.9Kohms resistor?

timmeh87 · Post by **timmeh87** » Wed Mar 29, 2006 7:27 pm

all the values inbetween work too. the output will just be a bit higher or lower than it says.

but. when you buy a resistor, their values uaully have an error of 5% or 10%, so it wont be the exact value anways.... i still say use a variable resistor, so you can adjust the output however you want it to be.

XFactor · Post by **XFactor** » Wed Mar 29, 2006 7:40 pm

I think i am going to go with just a standard resistor since it's the simplest solution. Would I be fine with a 1/4W 1.8Kohm resistor here?

timmeh87 · Post by **timmeh87** » Wed Mar 29, 2006 7:47 pm

yeah. i cant open the datasheet right now because adobe is copulate up. go to the lower side of 3.3v, watever that is. im personally going to give it the lowest it will take, probably about 3.0v

XFactor · Post by **XFactor** » Wed Mar 29, 2006 7:57 pm

For some reason, i tend to think that 3.3v was put there for a reason and some unknown issue will arise as the battery discharges. I dunno, most things i do oftentimes get messed up when i fool around with the limitations...

I am just careful i suppose...

daguuy · Post by **daguuy** » Wed Mar 29, 2006 8:31 pm

the minimum input voltage for the dc-dc is less than 5v so the battery discharging shouldn't be a problem

bioniclebert · Post by **bioniclebert** » Wed Mar 29, 2006 8:43 pm

the 3.3V line is odd. On some N64'S it takes quite a bit to withstand current draw, as well as functionality. I've had some N64's drop out at voltages yours was still working on. Ah well...

Now as far as the PSone 5V line, This is odd. Hadn't anyone ever tried powering it off of less voltatge?? I'm tracing its lines now...

Wait, why dosen't someone remove the 7805 to see if anything happens? Plus, it wouldnt be that hard to re attach. Plus, if what timmeh said is correct, the no 7805 should have no effect, due to it not even needing to function at 5.6v!

timmeh87 · Post by **timmeh87** » Wed Mar 29, 2006 9:24 pm

nono, the nintendo 64's 7805. the psone screen was runnign off the official power supply the whole time.

i dont even know if its a 7805, i just know its a 5v linear reg... maybe its LDO

Post by **gannon** » Wed Mar 29, 2006 9:38 pm

Have you actually checked the draw difference between 3.3V and 3V on the line? It might vary so it's ~ the same wattage.