{Collins} FW: Rectifiers



Wilson, I respectfully disagree with your conclusion. I've used solid state
replacements in my 30S1 for years with no problems. The 30S1 power supply
uses a choke input filter, with rather low capacitance (I'm going by memory
now, but I believe there are two 4uF caps in the HV supply), so surge
current isn't excessive. Also, the power supply is relay-switched, so
whatever surge current is present doesn't go through a switch.

By contrast, other commercial amplifiers, such as the 30L1 and the L4B, use
solid state rectifiers and a capacitor input filter, with an appreciable
surge current going through the on-off switch. Even in those amplifiers, the
designers didn't feel it was necessary to use a step-start circuit. One can
argue the merits of their decision, but the point is that solid-stating the
rectifiers in the 30S1 (and KWS1) can be done without worry. The resulting
voltage increase is only about 100V, and the regulation is also improved.

73,


Jim W8ZR

> -----Original Message-----
> From: collins-bounces@xxxxxxxxxxxxx [mailto:collins-bounces@xxxxxxxxxxxxx]
> On Behalf Of Wilson Lamb
> Sent: Tuesday, January 27, 2009 7:42 AM
> To: Clint Hasty; collins
> Subject: Re: {Collins} Rectifiers
> 
> Bad idea.  You have to deal with the considerable surge current when the
> diodes try to charge the filter caps instantly upon turnon.  Also, your
> voltage will be higher, possibly overstressing some very old components.
> Unless you are prepared to design/buy a soft start system and investigate
> the voltage level, you are askung for trouble.  I've just been evaluating
> some PS I built in the 50s and I'm going to stay with the 866s or 3B28s.
> Wilson
> ----- Original Message -----
> From: "Clint Hasty" <w4ch@xxxxxxxxx>
> To: "collins" <collins@xxxxxxxxxxxxx>
> Sent: Monday, January 26, 2009 8:14 PM
> Subject: {Collins} Rectifiers
> 
> 
> > Can anyone tell me where I can purchase solid-state rectifiers as
> > replacements for the 3B28's in the 30S-1. What's involved in the change
> > out ? any mods required after installing the solid-state rectifiers ?
> > Thanks
> > W4CH
> > Clint Hasty
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