TI 3.3V DC-DC, inductors and screen distortion

timmeh87 · Post by **timmeh87** » Mon Jul 10, 2006 7:38 am

well. the smaller one is air-core, it probably dosent have enough inductance. is the larger one air or iron core? i think everyone used something with some sort of ferrous core, which increases the inductance by something on the order of 1000 times.

also, whats the 'chainsaw intro' (never played that game...). some people have had problems with screen distortion related to loud noises coming out of the speakers.

Post by **marshallh** » Mon Jul 10, 2006 5:21 pm

Well, on jeff's L64, I just used a small green inductor (the ones that look like resistors) and it worked fine.

timmeh87 · Post by **timmeh87** » Mon Jul 10, 2006 6:51 pm

arent those things not rated for the kind of current the 64 draws?

codeman · Post by **codeman** » Mon Jul 10, 2006 6:59 pm

the small green ones are RF chokes, they're used usually to isolate RF and DC signals. The highest i've seen one rated for is 1amp, so extended use on a N64 might not be good...or it could be fine, who knows

superdeformed · Post by **superdeformed** » Mon Jul 10, 2006 9:30 pm

codeman wrote:the small green ones are RF chokes, they're used usually to isolate RF and DC signals. The highest i've seen one rated for is 1amp, so extended use on a N64 might not be good...or it could be fine, who knows

If the choke is just on the line from the battery to the regulator input then the current draw shouldn't be anywhere near 1 amp (unless of course the 3.3V line is drawing almost 2 amps, in which case you probably have bigger issues than lines on the screen

).

As for the lines, probably the easiest (surefire) way to see if it's sound related is to disconnect the audio channels. You could also try another game and see what happens.

codeman · Post by **codeman** » Tue Jul 11, 2006 8:05 pm

yeah, i guess you're right. After a quick test/calculation the TI PTH08080 has a relationship of I_input ~= 0.63*I_load for a 3.3v output and 7.2v input. Anyway, I just checked jameco real quick and the highest current choke they have is 495mA, and that was for a really small inductance of 0.68uH...if their labeling and stuff is correct, they tend to be off sometimes. I wouldnt use a choke if I ever got the ambition to make an N64p...

daguuy · Post by **daguuy** » Sun Jul 16, 2006 5:33 pm

try it without the diode. you're bigger inductor looks like the same size/kind as mine so i doubt it's the problem.