Re: LM31T as AC voltage regulator for Commodore computers PSU

From: Mike Stein <mhs.stein_at_gmail.com>
Date: Sat, 18 Jun 2022 17:12:41 -0400
Message-ID: <CAHHfo1scxMTMSd3=Zzj7-TRsptLW0vtE5MainB1TyJF7SXAg8g_at_mail.gmail.com>
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
>
>
Received on 2022-06-19 00:00:03

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