[Milsurplus] Any Tips on How to Drop the AC voltage to the Primary of a Power Transformer?

[Mack]

To all who posted to use a bucking transformer that is a most excellent idea 
and the one I'll adopt. Thank you everyone for your very rapid responses. 
Happy Thanksgiving!

73,

Mack de WB4MAK
www.nfarl.org
www.sedxc.org

--------------------------------------------------
From: "W RICHARDS" <wrichar2 at rochester.rr.com>
Sent: Thursday, November 26, 2009 13:32
To: "Mack" <mccormick_mack at hotmail.com>
Subject: Re: [Milsurplus] Any Tips on How to Drop the AC voltage to the 
Primary of a Power Transformer?

> Use a BUCK BOOST transformer. There should be info on the internet on how 
> to do it.
>
>
> Mack wrote:
>> I need to drop the AC input voltage to a power transformer to get the 
>> output voltage where I'd like it to be. I need to drop 120VAC to 85 VAC 
>> at .75A under no load conditions. I'm currently using a variable 
>> transformer to regulate the input voltage but would prefer a solution 
>> that is MUCH more compact so it would fit on the power supply chassis. I 
>> tried a household fan and incandescent controller but the high inductance 
>> of the transformer primary causes the fuse to always blow using this 
>> technique.
>>
>> I've considered using an approx 46 ohm 40W resistor but I'm not sure 
>> about the voltage regulation under intermittent (CW) load. Are there any 
>> better techniques than those I've described here?
>>
>> In case you're wondering about the project: It's my current ARC-5 
>> receiver, transmitter, modulator restoration. I'm using one power supply 
>> for all three pieces. The only HV transformer I had it my junk box 
>> produces 800 VDC at 120VAC input. I'd like to run the output plates on 
>> the transmitter at 550VDC. The power supply output also has taps for the 
>> screens, receiver, and oscillator (which is regulated with a 200V 50W 
>> zener). This is a VERY stiff HV transformer and is rated at 1A output. 
>> I'm also using filtered 12.6VDC for the tube filaments as suggested.
>> Thanks in advance for any ideas.
>> 73,
>>
>> Mack de WB4MAK
>> www.nfarl.org
>> www.sedxc.org
>> ______________________________________________________________
>> Milsurplus mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Milsurplus at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>
>