Re: LM31T as AC voltage regulator for Commodore computers PSU

Here you find them in dollar stores and box stores like Walmart etc.; FWIW
all the multi-voltage ones I've seen and used have been linear.

Just ask one of those German tourists that are taking over your country to
bring one next trip ;-)

m

On Sat, Jun 18, 2022 at 5:20 PM <tokafondo_at_tokafondo.name> wrote:

> I will only say that this is an actual Commodore (and retro computers)
> desert. And most 9V adapters I've ever seen are from xDSL routers, AP and
> modems, long ago discarded.
>
>
>
> 18 de junio de 2022 22:12, "Mike Stein" <mhs.stein_at_gmail.com
> <mhs.stein_at_gmail.com?to=%22Mike%20Stein%22%20%3Cmhs.stein_at_gmail.com%3E>>
> escribió:
>
> Well, he's in Spain and you're in Italy; maybe you treasure the old
> traditional ways more than he ;-)
> I don't know offhand how constant the 9V load of a C64 is but I would
> think that a carefully selected resistor with maybe a couple of Zeners to
> clamp any overvoltage might do the trick.
> m
> On Sat, Jun 18, 2022 at 2:27 PM Francesco Messineo <
> francesco.messineo_at_gmail.com> wrote:
>
> On Sat, Jun 18, 2022 at 5:42 PM <tokafondo_at_tokafondo.name> wrote:
> >
> > TI's version of the LM317T's datasheet has something interesting to see
> in its page 15.
> >
> > It can be seen only in TI's datasheet, and not others AFAIK.
> >
> > They show how to use two LM317T IC in a way that from a 12VAC source,
> take it down to 6VAC. I'm sure that with changing the values of the
> resistors needed, 9VAC can be got, instead of the 6VAC of the example.
>
> it is actually AC in the sense that there will be alternating polarity
> voltages, however that circuit will clamp the waveform voltage to 9V
> (or whatever you chose) as long as the input voltage is greater than
> the set voltage. So you'll get a kind of "flat-top" waveform.
> I'd say it's not ideal (it adds high frequency harmonics, both LM317
> need to be heatsinked...)
> I have never had any difficulty in finding 9VAC transformers.
>
> Frank IZ8DWF
>
>
>
>