Amplitude modulate variable regulator

Fri Jan 20, 2012 4:33 am   

"Glenn Myers"


** The TO-3 stage cannot sink ANY current, you will have to rely on the load
to do that.

The main limit on the voltage rising is C3, the 100uF cap - with a 3A
current limit, the max possible rate is 30,000 volts per second. This
equates to a 6 volt peak sine wave at 800Hz.

There is no simple way to make it voltage controlled - but maybe an LDR
with LED drive as one arm of VR1 would allow rapid adjustment.


.... Phil

Fri Jan 20, 2012 8:34 am   

Thanks guys. I think I've got the picture now .. or at least enough to
try a few things.

Glenn

Fri Jan 20, 2012 12:30 pm   

On Jan 20, 4:08 am, "P E Schoen" <p...@peschoen.com> wrote:

<snip>


The particular virtue of the 723 is that is uses a voltage reference
based on a avalanche breakdown (at 7.15 +/-0.35V), which is quieter
than the band-gap references used in more modern regulator chips, and
some people keep on using the part for this reason.

In every other respect it's pretty diabolical.

<snip>

--
Bill Sloman,

Fri Jan 20, 2012 1:22 pm   

"Dill Slowman"

The particular virtue of the 723 is that is uses a voltage reference
based on a avalanche breakdown (at 7.15 +/-0.35V), which is quieter
than the band-gap references used in more modern regulator chips, and
some people keep on using the part for this reason.


** How dopey.

Vref is accessible for RC filtering of the noise - so it can be easily
reduced to the uV level.


In every other respect it's pretty diabolical.


** Like hell it is.



.... Phil

Fri Jan 20, 2012 2:37 pm   

On Jan 20, 1:22 pm, "Phil Allison" <phi...@tpg.com.au> wrote:

Perhaps. I'm just reporting facts, not expressing an opinion.


So how do you like it's mechanism for implementing a current limit?

--
Bill Sloman, Nijmegen

Sat Jan 21, 2012 6:32 am   

"Dill Slowman"

Perhaps. I'm just reporting facts, not expressing an opinion.


** You just expressed another wrong opinion.



So how do you like it's mechanism for implementing a current limit?


** LOL !!

The man's about as a sharp as a bowling ball.....



.... Phil

Sat Jan 21, 2012 10:21 am   

On Jan 21, 6:32 am, "Phil Allison" <phi...@tpg.com.au> wrote:

Where's the Phil Allison we've come to expect? Have you found a new
anti-psychotic?

--
Bill Sloman, Nijmegen

Sat Jan 21, 2012 3:32 pm   

On Thu, 19 Jan 2012 19:09:14 GMT, glennmyers_at_intergen.com (Glenn
Myers) wrote:


You can modulate the output of this circuit by disconnecting R13 at
the pin six connection, setting the pot for maximum, then applying a
0-7v5 dc signal to the open end of R13.

The output will be a Vmod/7v2 fraction of the pot's original setting,
and the pot can still be used as a manual full scale adjustment, while
the external modulator is in effect.

This modulating signal could be the output of a filtered PWM, PAM, FM,
DAC or whatever.

RL

Sat Jan 21, 2012 4:35 pm   

On Sat, 21 Jan 2012 09:32:07 -0500, legg <legg_at_nospam.magma.ca> wrote:



An emitter-base resistor (1K-4K7) across TR1.
A series collector resistor for TR1.(~100R)
A fuse in series with the line input.

TR2, not being diffused mesa (as it would have been at the time of the
original design) needs foldback current limiting:
A series base resistor for TR3. (~5K)
A Vce-dependant offset provided by a resistor from base of TR3 to the
output. (~100xRB of TR3) This should ~halve the output short circuit
current. If you still want 3A of short circuit current, you should use
a heftier pass transistor, or two 2n3055s in parallel, with ~ 0.3R
emitter ballasting.

At 3A, C1 will likely also need to be larger.

A 1N5401 across the output terminals may ease series/parallel
operation of multiple units and is pretty standard in even the
cheapest products.

RL

Sun Jan 22, 2012 12:22 am   

On Sat, 21 Jan 2012 09:32:07 -0500, legg <legg_at_nospam.magma.ca> wrote:


Thanks for the expert technical advice. This is something to actually
work with.

Glenn