[ICOM] Internal PS question

[Mort Arditti]

Another important detail to consider with switching power supplies and
electrolytic capacitors is the capacitor characteristics.

In switching power supplies, the pulse currents through some capacitors may
be high.  Therefore, the Equivalent Series Resistance (ESR) of the
capacitors must be as low as possible.  The capacitors will heat up simply
as a result of the internal power dissipation according to the relation
P = I^2 * ESR and the Duty cycle of the current.  The peak dissipation may
be very high which will slowly destroy 'average' type capacitors.

Capacitor manufacturers make special electrolytic capacitors with low ESR
for use in switching power supplies.  Another approach is to use several
capacitors in parallel, thus the peak currents will be distributed (not
exactly equal currents) among the multiple units.

The issue of high ESR also applies to the various families of ceramic types.

Mort,  NA6MA

-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of jkolin at optonline.net
Sent: Tuesday, March 06, 2012 8:21 PM
To: ICOM Reflector
Subject: Re: [ICOM] Internal PS question

Electrolytics are the only components containing liquids and are usually the
weak links in electronic circuits. If you've ever rebuilt an old piece or
gear you know the first things to replace are all the electrolytics.My
experience has shown the more heat that electrolytics are subjected to, the
quicker they lose their value and the shorter their life. The heat tends to
escalate the drying of the liquid or gel used in electrolytic capacitors.
Loss of capacitance can negatively affect performance of circuits and can
result in a radio not up to original specs.This is the main reason I always
purchase transceivers without internal pwr supplies and why I add a small
low speed muffin fan to keep radios cooler than the internal fans supplied
with radios.Jay,  NE2Q----- Original Message -----From: Steve Date: Tuesday,
March 6, 2012 10:59 pmSubject: Re: [ICOM] Internal PS questionTo:
ICOM Reflector > Are the built in supplies really of the switching type >
especially in > the older 735?> I've always assumed they were just good old
linear type supplies > with > no noise problems. I guess I never really
looked to see if there > is > room inside for the large transformer of a
linear type supply.> > > At 08:57 PM 3/6/2012, you wrote:> >I have an
Icom IC-736...Has built in AC supply, built in tuner, 6> >meters, LARGE
display, and analog S meter....For these items, > it is one> >of my favorite
rigs.> >It works great!!!> >....Dave> >> >On 3/6/2012 8:11 PM, John G.
wrote:> > > On the older Icoms like the 740 and 751A that have an > internal
PS > > option, is it usually better to get one with or without the > PS?  It
> > would be convenient to just plug the rig into the wall, but > how > >
quiet are these older switching PS?  Also, does the heat they > > generate
affect the reliability of the radios at all?> > >> > > 73 John> > > AF5CC> >
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