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Re: [Amps] SCR to adjust 240v to 200v

Subject: Re: [Amps] SCR to adjust 240v to 200v
From: Jim Durham <>
Date: Sat, 13 Aug 2016 11:11:33 -0400
List-post: <">>
Thank you, Boye (OZ7C) and the others that replied. I think I did not explain my project clearly.

First of all, yes, I know about buck transformers. I am using a Variac, which does the same thing and also allows me to adjust the input AC voltage. The Henry 2K has the filament voltage supplied from a winding on the plate transformer, so, with the Variac, I can adjust the input AC voltage to give about 9.8 volts for the filaments, which is ideal and produces 3000 volts for the plates.

A large buck transformer or Variac requires an external box, which is what I am using now. They won't fit in the amplifier without seriously hacking up the cabinet. I don't want to do that.

So, I was just asking if anyone on Amps had tried using an SCR to control a large choke-input power supply ? That sounds attractive and would fit in the cabinet, but also might damage the power supply choke by applying non-sinusoidal power (the 2K-2 has a choke input power supply). That was my question.

Thanks to all,  I should have explained more clearly what I was asking.

73 de Jim, W2XO

On 08/13/2016 12:52 AM, Boye Christensen wrote:
Hi Jim
Do no know that amplifier.
Can't recoment it.
Fist this will be ok to reduce the filament power.

Depending on what type of recifier type HV is?
If is a standard recifier with capitors the peak voltage will still be high.
If it is a choke type  like Henry 8K this need a sinus voltage.

The best you can do is to find a transformer Pri/sek 200/40 Vac 15 Amp and insert it in
phase the secundary vindings with the mains voltage to reduce voltage

73 Boye. OZ7C

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