Re: Amplifone +/- 24v regulation

On Fri, 10 Jul 1998 09:01:00 -0400, Joel Rosenzweig <joel-r@an.hp.com> wrote:

>Zonn,
>
>I wanted to thank you for taking the time to respond so thoroughly to my
>question regarding the Amplifone current regulation. That was really
>awesome to see a schematic accompany the reply!!!
>
>If I may be so bold .. what does the complementary circuit look like for
>the 7924/2N3716? I have this vision of swapping some combination of the
>transistor leads incorrectly. As you can tell, analog circuit design is
>not my area of expertise. :-) I mean, umm, given that this email is
>getting archived, shouldn't we have the circuit drawn out, just for the
>record? You know, just in case some other misguided soul tries to get
>rock solid performance out of his Amplifone this weekend? Yeah ..
>that's it.

The 7924 looks nearly the same:
 
            +------------+--- ----------+
            | ^ E C / |
            | \ / 2N3716 |
            | 6 ohm 1/2 watt ----- |
            | +--/\/\/---+ |B |
            | | | | ------- |
 -unreg ---+--+---X X----+-----+----|7924 |---+---- -24v reg
                    ^ in ------- out
              Cut trace here |gnd
                                        |
                                       ---
                                        -

as opposed to the 7824:

            +------------+--- ----------+
            | \ E C / |
            | V / 2N3792 |
            | 6 ohm 1/2 watt ----- |
            | +--/\/\/---+ |B |
            | | | | ------- |
 +unreg ---+--+---X X----+-----+----|7824 |---+---- +24v reg
                    ^ in ------- out
              Cut trace here |gnd
                                        |
                                       ---
                                        -

I've marked the Emitter, Base and Collector of the transistor, and the IN, GND
and OUT of the regulators.

The thing you must be careful about is the pinouts of the regulators. The IN,
OUT, and GND pins are numbered differently between the 7824 and the 7924. (Just
from memory I believe the OUT pin is the same on both regulators and the IN and
GND is swapped between them. Be careful and make sure to look this up in a data
book or something.)

Use insulating washers when mounting the transistors to a heatsink (you'll have
to find a heatsink), check for shorts, blah, blah, blah...

This circuit worked fine on a WG monitor, but it meant a lot of rewiring from
the original LV regulator. Anders design is so much easier to install, that the
LV2000 is definitely the way to go on a WG.

As far as the Amplifone goes, the above circuit is a very easy one to implement,
without the need for a PC board.

It'll be interesting to see how the beefed up regulators effect the Star Wars
explosion sequence!

-Zonn

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Received on Fri Jul 10 13:46:50 1998