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Re: [Amps] Tube regulators

Subject: Re: [Amps] Tube regulators
From: Radio WC6W <>
Date: Sun, 25 Jul 2004 07:28:00 -0700
List-post: <>
On Fri, 23 Jul 2004 15:05:40 -0400 Will Matney <> writes:

Hi Gene & Will,

> Gene,
> Yes, that can be done easily. However, not having the safety of the 
> isolation from a transformer can be hazardous. The chassis would have
> be grounded to the line ground. The problem is that in some older
> the outlets may not be grounded or even hooked up backwards! 

   Or both!

> This being the case, if someone would be touching the chassis then a
ground, a 
> possibility of electrocution would be present.

  Especially when one goes to hook up the grounded antenna lead to the

  Please don't misconstrue that I in any way recommend this topology but,
theoretically, a "power good" (hot,neutral,gnd) circuit might prove
useful.   It could inhibit a double pole power relay, that switches both
hot & neutral wherever they are, and/or activate an audible warning.   

> Ok, now to how it could be done. Using a simple series pass transistor 
> regulator could be made.

  Not a great idea.  Lots of dissipation incurred.  And when (not if!)
the pass transistor fails full line V would end up on the pricey RF
transistors.   A crowbar circuit would be a must.

> The hot lead being rectified and regulated with 
> the ground going directly to the chassis and line ground.

  A bad idea as noted a couple paragraphs above.


> Last, an isolated chassis might be thought of. The regulator being
> upon a chassis or pc board which it's ground was not connected to 
> the chassis. If the chassis was then grounded and if a possible leak to

> the chassis happened, the line fuse should open. This could be done
> an amplifier too if the DC ground was connected to the chassis with 
> suitable capacitors allowing only RF to be there for shielding and 
> connection to the coax. I played with some circuits such as this with 
> success but that was long ago. The problem is that whatever the 
> power supply is running could still have voltage on its chassis due to
> faulty outlet. So, for personal applications it may be ok, but for 
> commercial applications with liability, it would be a big NO-NO!

  Nothing protects against the happenstance of: missing ground, reversed
hot/neutral.  If there is any path from the line to the chassis, it is
going to hurt!!!
  If the entire amplifier/power supply assembly is "floated" inside a
grounded cabinet and then fed by RF input and output transformers it
would be as fault tolerant as a typical design.

> Will Matney
> From: "Gene Bigham" <>
> Subject: [Amps] Tube regulators
> "With all this discussion about tube regulators I have a question. Is 
> there a cheap way to make a direct AC mains supplied power supply for 
> approximately 48 to 50 volts DC for a solid state amplifier using some 
> type of regulator off the 110-120 volt AC line? I keep wondering about 
> rectifying the 110-120 volts AC and then using some form of a regulator

> for the high current 48-50 VDC required?"

   Unless you are trying to fit a specific space, 48 volts is a fairly
standard power supply voltage.  One can find surplus switching power
supplies up to 2KW capability with single phase AC power or more with 3
phase input.

73 & Good morning,
  Marv WC6W 


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