LM317T regulator

[keko]

Hi guys. I want to build a dedicated PS to my new pedalboard, and chose the 'ultra clean power supply' from ggg.
The thing is that I can't find (yet) a 25v transformer. All I have is several PC powered speakers (yes, speakers)

So i tore them apart, and the transformer inside (220v) only puts 9.4v AC. I traced the current path and I can get 14vDC from the board inside. But it's not regulated, less filtered.

Can that 9v AC be made to work with the LM317T, or put other way> How many volts will you drop when regulating using that chip?

I've read the datasheet, but don't understand much of it.

Probably this transformer is very low on de Amperes side, but I just want to give it a try as a learning exp. while I get a suitable trasnformer.

Thanks!

[niftydog]

somewhere on the datasheet (fig 8 on mine) there's a graph called "drop-out voltage" that will tell you all you need to know, and then some.

worst case is around 2.5 - 3 VDC.

Keep in mind that when you're multimeter shows 9.4VAC, your actually getting more like a 13V peak-peak waveform.

Rectify this and you get around 11.8VDC, which might be just enough for the regulator to produce a decent 9VDC out.

[keko]

Mi datasheet seems to be different. Could you please send yours over?

keko at keko dot cl

thanks!

[niftydog]

page 3, figure 3

emailed as well.