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Re: [Amps] 3-500Z glitch resistor

To: <>
Subject: Re: [Amps] 3-500Z glitch resistor
From: David G4FTC <>
Date: Mon, 8 Sep 2008 16:18:44 +0000
List-post: <">>

>> Everyone seems to agree that a glitch resistor between the plate choke
>> and the HV supply is a good idea, to limit huge current surges due to
>> arcs caused by gas, etc. But recommendations for the value seem to vary
>> all over the map.
> I like the look of Vishay RCH series or similar (Tyco do an
> equivalent). The 50W version is rated at 5.5W without heatsink and
> is specified to handle 2500Vrms (that's 3500V peak) short term
> overload. If you want to bolt it to a panel for heatsinking, the
> insulation is rated for 3500Vrms (5kV peak).

Checking page 4 of the datasheet for the RCH50
shows a maximum overload capability of about 50 Joules.

A capacitor bank for a linear of 50uF charged to 3kV will deliver about 225 
Joules and
under glitch conditions the resistor will be absorbing most of this power, more 
the power supply doesn't have glitch detection/protection and remains connected
to the mains.

In order words to be safe you'll need about five RCH50 resistors in series.

I don't know what energy the tube can absorb under flash over conditions 
damage and this will also influence the selection of the resistor.


David G4FTC

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