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Re: [Amps] AL-1200 Low High Voltage (HV)

To: "John" <aa6qn@aa6qn.sytes.net>, <amps@contesting.com>
Subject: Re: [Amps] AL-1200 Low High Voltage (HV)
From: "Tom W8JI" <w8ji@w8ji.com>
Date: Sun, 20 Aug 2006 10:50:52 -0400
List-post: <mailto:amps@contesting.com>
> Current: I measured input across both line fuses and its a 
> healthy
> 250vac. Measuring each input winding pair on the primary 
> side of the
> transformer
> Pair 1 Terminal 1 (Yellow [Black/Wht lead]) and Terminal 
> 3(Clear [Black
> Lead]) is 124.6vac
> Pair 2 Terminal 4 (Red [Brown/Wht lead] and F1 [Brown 
> lead]I get 124.7vac.
>
> With the above configuration I show 3000v on HV

If that is an original transformer, the meter is off.

> So the question now is what else can affect the HV? 
> Something around the
> plate end of the tube? or RF Choke?

 There is nothing that can make the HV actually be 3000 
volts at idle without also causing a lot of heat and smoke. 
There is normally about 10% voltage sag from no load to full 
load. If you see significantly more sag than that and don't 
see smoke pouring out it has to be the power mains.

The 470uF is a large waste. I hope those caps are 525 surge 
rated or use 600V foil. 220uF already puts the supply well 
over the knee in voltage regulation. Replace the 1 meg ohm 
voltage multipliers with new 1 meg ohm HV rated resistors 
and the HV will be back to normal. With that mains voltage 
it should be 3600 volts.

73 Tom 


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