[Elecraft] Unknown Schematic Symbol - Need ID

Wed Jan 29 15:39:00 2003

That sounds like a thermister.  The resistance changes with temperature
change.  There are two types that I'm aware of POS and NEG.  Pos
thermister rises in resistance as temperature goes up and the opposite
for the negative type.  These are usually used to trigger a protection
circuit if a component was getting too hot.  They are available at most
electronic supply stores.

I hope this helps,
Robert VE3RPF

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Mark A. Sandler
Sent: Tuesday, January 28, 2003 5:52 PM
To: [email protected]
Subject: [Elecraft] Unknown Schematic Symbol - Need ID

Hello Fellow Elecrafters:

I'm in the process of trouble shooting and repairing my switching power
supply.  One of the damaged components has a symbol on the schematic
that
I'm not familiar with, and does not show on my "Handbook" chart of
schematic symbols.

I believe it is a temperature variable resistor.  The symbol looks like
a
resistor with an oval around the squiggly line.  It has two leads.  The
part is marked TH4 - 6.8K.  There are four of these on the power supply
board...TH1 to TH4, with varying values.  

Any confirmation of my analysis??  What are they called??  Can you get
them at Radio Shack or another "local" electronics parts stores??

Thank you in advance, 
Mark - K7MAS
K2/100 #874

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