[Elecraft] KPA500 - linear power supply

[Guy Olinger K2AV]

Every switching supply I have ever owned eventually failed, except my
carry-around 18 amp job for porting my K3, and the current power
supply in my PC, one week old after the previous failed.  Most of the
switchers were in PC's.  I have never had a linear supply fail.
Everyone is trying to make switchers light, cheaper, less components,
less fan, less everything that makes one reliable.

A toroid transformer's external flux is WAY down from a standard transformer.

And in the strange case that you actually had it fail, you could
rewind it yourself.  But the weakest point in a transistor amplifier
is ALWAYS going to be the transistors.  Abuse the amp, and the
transistors will be the first to go, if at all, not the power supply.

73, Guy.

On Wed, May 11, 2011 at 11:40 AM, Lee Buller <k0wa at swbell.net> wrote:
> A couple of years ago, I looked hard at the THP amps at Dayton.  They were using
> linear supplies as well.  If I remember right, the PS voltage was 60 volts no
> load...and 48 volts under full power.
>
> I think there might be a cost issue here as well.  Less parts for a non
> switching power supply...less complexity too....and field repairable as well.
>
> Lee - K0WA
>
>
>  In our day and age it seems that Common Sense is in short supply.  If you don't
> have any Common Sense - get some Common Sense and use it.  If you can't find any
> Common Sense, ask for help from somebody who has some Common Sense.  Is Common
> Sense divine?
>
> Common Sense is the image of the Creator expressing revealed truth in my mind.
> -  John W. (Kansas)
>
>
>
>
>
>
> ________________________________
> From: Johnny Siu <vr2xmc at yahoo.com.hk>
> To: F5vjc <foxfive.vjc at gmail.com>; Henk Remijn PA5KT <pa5kt at remijn.net>
> Cc: "elecraft at mailman.qth.net" <elecraft at mailman.qth.net>
> Sent: Wed, May 11, 2011 8:39:10 AM
> Subject: [Elecraft] KPA500 - linear power supply
>
> I notice KPA500 is using a linear power supply.  The technology of switching
> power supply is now very mature.  Is there any reason why linear PSU is used
> instead of switching PSU in KPA500?  I just think a switching PSU will make
> KPA500 more lighter and the linearity of the amplifier will not be affected by
> fluctuation in supply voltages.
>
> A lighter KPA500 will make it more portable for Dxpedition.  My questions may be
> discussed somewhere in the past.
>
> Any advice?
>
> TNX & 73,
>
>
> Johnny VR2XMC
>
> 從︰ F5vjc <foxfive.vjc at gmail.com>
> 收件人︰ Henk Remijn PA5KT <pa5kt at remijn.net>
> 副本(CC)︰ elecraft at mailman.qth.net
> 傳送日期︰ 2011年05月11日 (週三) 9:26 PM
> 主題︰ Re: [Elecraft] KPA500 - stacking possibilites
>
> As the KPA 500 uses a linear PSU there obviously is a mains
> transformer within the cabinet.
> I know this is a toroidal type transformer, which is good, but can we
> assume that placement of the Amp with respect to the K3 is non
> critical, for magnetic hum coupling.
>
> How immune is the K3 to this effect? Has placement of the KPA 500
> w.r.t. the K3 been tested  for any ill effects?
>
> 73, Deni
> F5VJC
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