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Re: LF: Decca component

To: [email protected]
Subject: Re: LF: Decca component
From: "Rik Strobbe" <[email protected]>
Date: Mon, 27 May 2002 10:11:54 +0200
In-reply-to: <000701c204c9$aece79e0$416368d5@oemcomputer>
Reply-to: [email protected]
Sender: <[email protected]>

The dead Tx unit still works but not very well. A component across one of
the transistors burnt out. I have a diagram but do not recognise the symbol
(perhaps a temperature variable resistor?). It is called R31V and the symbol
looks like a preset potentiometer, but it looks just like a red disc ceramic
capacitor.

Hi Mike,

it's most likely a varistor. These components have a very high resistance that sinks rapidly once a certain voltage is exceeded. They are often used to avoid overvoltage (spikes etc...) over semiconductors. The important thing you need to know is the breakdown voltage of the varistor. Typical this is about 70 .. 90% of the max. allowed voltage over the semiconductor, but in rugged equipement (as the decca units) it might be less (50% or so) to be on the save site.

73, Rik  ON7YD



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