I think both Mark (the original poster) and I were WAITING for you to jump in
and offer your comments, but you were out-of-service for the last few weeks and
your absense was felt.
So today's questions are (in your experience):
1. Does the supply just fold-back the current if the output is shorted?
2. Does the supply just fold-back the current if the crowbar SCR fires?
3. Can anything simple be done to prevent the crowbar from firing when the
supply operates in a strong RF environment?
4. Is the crowbar firing due to RF, or is the output voltage actually going
high enough to trip the SCR, thus making it fire for the purpose it's there for?
Hopefully the answers you post will be more detailed than: "It depends",
"Maybe", or "Yes and No".
Bob M.
======
--- On Fri, 12/26/08, skipp025 <skipp...@yahoo.com> wrote:
> From: skipp025 <skipp...@yahoo.com>
> Subject: [Repeater-Builder] Re: Astron P/S question
> To: Repeater-Builder@yahoogroups.com
> Date: Friday, December 26, 2008, 12:55 PM
> > "wb6fly" <wb6...@...> wrote:
> > I should point out that Astron has made several
> significant
> > changes to the RS-series regulator boards over the
> past 20 years,
>
> Amen... notice how I've been steering clear of this
> thread? There
> are/were so many board revisions and design shortfalls that
> I just
> didn't want to patch their circuit, which is the reason
> I choose to
> start making my own.
>
> > For what it's worth, almost every Astron regulator
> board I've
> > seen has a few extra resistors or capacitors added to
> it, as
> > if each one was "customized" during
> manufacture.
>
> Yep, parts were added to make the main board work for
> different
> models. As one example the crowbar circuit on some models
> is
> right on the regulator board, others external and case
> mounted.
> I have a parts table for the various Astron Regulator
> boards
> so if you smoke a resistor (or any other part) I can
> probably
> tell you the original value.
>
> > According to Fred, Astron's lead technician, some
> components
> > are still being changed to make the units more stable-
> decades
> > after the original design!
>
> They still appear to have not closely read and applied the
> LM-723 chip engineering data sheet. My original replacement
>
> regulator board is still pretty much the same circuit
> although
> the next generation pc board will appear slightly
> different.
>
> Since there are so many regulator board part versions based
> on
> the model and type of supply... it's hard to single out
> a specific
> problem unless I/we know your a bit of the internal details
>
> about your supply.
>
> The original problematic regulator circuit suffers from
> susceptibility
> to RF, less than optimal engineering in the SCR detect and
> trigger/
> fire circuit, sometimes not so great parts placement and
> soldering.
>
> It's sometimes hard to know what power supply regulator
> board
> version and chassis layout you really have without lifting
> the
> lid to have a look.
>
> cheers,
> skipp
>
> skipp025 at yahoo.com
