Hello there,
The LM-723 regulator is often placed in
under engineered circuits. There are on-board
internal amplifier loops, which are
susceptible to RFI and high frequency glitches
- noise. Proper LM-723 pre-regulation is another
common circuit shortfall. The end result is
often seen as erratic operation, crowbar circuit
firing and regulator failure. Crowbar firing
is more common in aged units with older filter
capacitors under relatively heavy loads.
Many Astron power supplies work well for decades,
a lot of the problematic supply's surface in
operational circuits with higher impedance and
reactive loads. The load impedance and current
demand presented to the supply can be a big
factor in its reliability.
I have an actual exact drop in replacement Astron
Regulator Board, which has improved LM-723
pre-regulation, additional RFI and noise bypassing
and some minor value changes. I test each
regulator for proper operation, I've never had
one fail, nor the crowbar circuit fire, even at
high-level RF sites.
It's not Astron's fault� they are certainly not
the first, nor the last person to miss-understand
or overlook the LM-723 regulator layout. I've
found very few LM-723 regulator circuit designs
done really well.
The 723 Regulator is an excellent building block,
but making one play well with a nearby 50kw
broadcast transmitter can be a test of ones
engineering skills. Fortunately, the data sheet
has all the required information. Much of the
mentioned data sheet information is often
overlooked.
My exact size/named/replacement drop in regulator
board is $34.95 plus $4.35 S&H. You simply unscrew
and unsolder your original regulator board after
noting (and writing down) the original wire
connection points.
The replacement board drops right in and you solder
the corresponding original wires to the same locations.
The board connection points appear almost exact (but
the circuit is not).
If your power supply was working before the retrofit,
you simply power up, test and go. Each regulator board
is tested before they are sent out.
If your power supply had previously failed, you
should first test the pass & driver transistors,
emitter ballast resistors and a few other small
items before you re-apply power the supply. Although
I hadn't originally made these boards available for
resale, I will provide an instruction sheet with some
additional test & repair information. With some
revision, the updated regulator circuit is similar
in appearance to the original Astron Design with
circuit and part value updates in place.
Hope that helps
Cheers,
Skipp
Skipp025 at yahoo.com
www.radiowrench.com
www.radiowrench.com/sonic
: Hi Skipp,
: Could you please post the info about your
: upgraded circuit board for the Astron RS-35
: to the list? Many of us would like to know
: more about it.
: Thanks much.
: Doug VA7DD
> "Joe D" <[EMAIL PROTECTED]> wrote:
> I have an Astron RM-35M that runs for a few hours and
> then crowbars.
>
> Someone tell me more about this upgraded circuit by Skipp.
>
> JoeD
> [EMAIL PROTECTED]
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