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Re: [TenTec] OT: Scopes

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] OT: Scopes
From: Ken Brown <ken.d.brown@hawaiiantel.net>
Reply-to: ken.d.brown@hawaiiantel.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Mon, 20 Feb 2012 09:58:44 -1000
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>

> What if I want to look at the plate?
If you are looking at low level stages with only 100 volts DC or so you 
could use a 250 Volt rated probe. The probe rating should be as high as 
the peak AC voltage PLUS the DC voltage that is at the point you are 
connecting it. Generally two times the DC voltage will be good enough. 
The AC signal generated at the plate of a tube is seldom greater than 
the DC plate voltage. If the tube has 125 VDC on the plate you should 
use a 250 Volt rated probe.

When making these kinds of measurements it is best to connect everything 
with the power off, and then keep your hands off the probe when the 
power is on.

> The RF or Audio signal from the RX stage is passed on through a 
> capacitor to
> the next stage, otherwise you would have the high voltage on the input 
> of
> the next stage.   Measure on the other side of the capacitor, not on the
> high voltage side.
> You need to consider the voltage specs of the probe, but most should be 
> good
> for 250v.
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