I would like to see a drawing or description of exactly where you placed the
resister and the value and where you connected the led. Interesting.
I lost one 723 chip in a RS20M but that was all. I since bought 25 of them
($25 minimum order) and some other stuff (the chips were something like 67
cents each) because the only one I could get at the time was from Radio
Shack for over $6 and I had to drive 80 miles round trip because I had to
have it right away. I was net control and had over 1500 bicycles arriving
in the morning. I now have a spare 723 chip inside each of my power
supplies, RS70M, RS35M, and the RS20M (actually I just sold the RS20M). I
have never lost another and the only other problem I am aware of was blamed
on a shorted transformer but I really question the diagnosis and I never did
see it.
73, Jim
----- Original Message -----
From: "Jim P" <jvpoll@dallas.net>
To: <rrath@charter.net>; <dgsvetan@rockwellcollins.com>
Cc: <rfi@contesting.com>
Sent: Saturday, May 26, 2007 7:11 PM
Subject: Re: [RFI] RFI from Astron power supply
> I have to beg to differ that this series of Astrons (the
> linears like the RS-35M et al) are all that 'reliable'.
>
> I have had to replace the LM723 (I think it is) regulator
> on a couple of these and have since made a circuit
> change (added a resistor) to give the regulator a better
> chance at life.
>
> The 'symptom' of failure was the inability to deliver rated
> current without voltage 'sag'.
>
> It is also a good idea to add an LED (with suitable series
> resistor) across the unregulated DC side of the transformer
> and make this visible/viewable through one of the slots on
> the top of the supply towards the rear.
>
> This does two things: you will know when you 'lose' the
> regulator side of the PS but know you have unreg DC and
> this also provides a bleed-off path. My recollection is that
> there isn't a suitable bleed-off on that series (maybe the
> earlier ones anyway which may be what I have.)
>
> Jim P // WB5WPA //
>
>
> ----- Original Message -----
> From: <dgsvetan@rockwellcollins.com>
> To: <rrath@charter.net>
> Cc: <rfi@contesting.com>
> Sent: Friday, May 25, 2007 10:11 AM
> Subject: Re: [RFI] RFI from Astron power supply
>
>
> > Rod,
> >
> > I presume that the Astron supply in question is the SS-35 or SS-35M.
Those
> > are switching power supplies, but are among the best I have ever seen
> > regarding RFI to HF or other radios. I have been using an SS-35M for
more
> > than 3 years now and think it is great. Being an EMC engineer, I was
very
> > wary of having a switcher in my station (I operate 160m thru 70 cm, so
> > that's a lot of spectrum that could get messed up). If the Astron
> > switcher is creating RFI, I am guessing that something has gone wrong
with
> > the internal circuits and you would probably do best to contact Astron.
> >
> > Now, if your power supply is one of their very reliable linear series
> > (which weigh a proverbial "ton"), then I can just about guarantee that
> > something has gone wrong with the internal voltage regulator that drives
> > those big pass transistors on the back of the supply. It is not
uncommon
> > for linear regulators to "take off" and oscillate, creating sometimes
> > extensive RFI. Sometimes the chip itself is bad, and other times the
> > problem can happen either because no by-pass cap was used at the input
> > side of the regulator or the cap is there but went bad. Again, contact
> > Astron.
> >
> > Either way, I would hope that with only 20 hours of use that the supply
is
> > still within the 1 year warranty. If not, you'll still do best (in my
> > opinion) to contact Astron and return it. Trouble shooting either power
> > supply will involve use of a decent oscilloscope (having at least 50 MHz
> > bandwidth) and/or a spectrum analyzer. Either instrument should allow
you
> > to find the problem within minutes.
> >
> > It would be helpful if you were to post which model Astron you have.
> >
> > 73, Dale
> > WA9ENA
> >
> >
> >
> > rrath@charter.net
> > Sent by: rfi-bounces@contesting.com
> > 05/24/2007 11:30 PM
> >
> > To
> > rfi@contesting.com
> > cc
> >
> > Subject
> > [RFI] RFI from Astron power supply
> >
> >
> >
> >
> >
> >
> > Hello to the list. I have a 35 amp Astron power supply that is giving of
> > RFI.
> > This p.s. has had less than 20 hrs use. I am charge of the Ham radios
for
> > our EOC, where we use this p.s. I just had the local power company RFI
guy
> >
> > come and we located 9 power poles that are giving off RFI as well as the
> > p.s. They will take care of the poles, I need to take care of the p.s.
> >
> > Any help on what to do to get ride of the RFI from the 35 amp power
> > supply?
> > The p.s. is giving off about an s-5 to s-7 RFI.
> >
> > Thank you for any help you can give.
> >
> > Rod KC7VQR
> > W7SCC Trustee
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
> >
> >
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
> >
>
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