[Amps] FW: Re[2]: HV limit for rfc-3 choke? / measuring RF blow-by

[Leigh Turner]

Hi Chris, such poking and probing lethal HV power supplies to measure their
AC ripple and / or any superimposed RF blow-by leakage is fraught with
danger for the unwary.

I am fortunate to have an old Tektronix P6015 high-voltage AC wideband
compensated probe in the lab cupboard for carrying out such investigations
relatively safely with an oscilloscope.

Sans such kind of accessory one would need to exercise extreme caution. One
could in the alternative rely on the calculated RF attenuation using the
filter network L and C and R values to ensure things are copacetic.

Placing a temporary resistive voltage divider chain across the PS would work
DC wise for facilitating a safe measurement, but likely be in gross error
for RF voltage at 1.8 MHz due to the stray capacitance and R-C filtering in
the divider string.

Leigh
VK5KLT

-----Original Message-----
From: Chris Wilson [mailto:chris at chriswilson.tv] 
Sent: Wednesday, 26 March 2014 6:14 PM
To: Leigh Turner
Subject: Re[2]: [Amps] HV limit for rfc-3 choke?

Hello Leigh,

On Wednesday, March 26, 2014,  you wrote:


> Excellent figuring Peter!
>
> An additional choke and bypass cap is almost essential to prevent
> deleterious 1.8 MHz RF blow-by into the HV power supply electrolytics.
>
> Mind you the HV "glitch" resistor also provides some attenuation of RF
> leakage when bypassed with a ceramic cap.
>
> Leigh
> VK5KLT


With a capacitive input filter HV supply, is there a safe way to check
whether RF is back feeding it? Thanks. And thank you Peter for
sending the excellent paper on RF chokes!


-- 
Best regards,
 Chris                            mailto:chris at chriswilson.tv