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Old 12th August 2003, 01:16 AM   #1
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Default capacitor schematic label question

on a schematic, i see some capacitors labeled as .001uF F.T.

what does 'F.T.' stand for?

if it helps, this is an old tube radio schematic (zenith) from ~1959.

what type of caps are these, probably? mica? or paper? or does 'F.T.' give the answer?

/andrew
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Old 12th August 2003, 02:25 AM   #2
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I`m guessing here but it could be FT= film type
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Old 12th August 2003, 04:16 AM   #3
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thanks.

sounds plausible, anyway!

/andrew
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Old 12th August 2003, 11:27 AM   #4
dhaen is offline dhaen  Europe
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F.T. Always used to mean FeedThrough.
This is a special type of cap that suffers no "series" inductance, and is suitable for RF.
Here's a picture:
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Old 12th August 2003, 11:39 AM   #5
Electrons are yellow and more is better!
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If you have the schematic I gather that the feed-through symbol doesn't look like a capaictor, more like a wire, 3 connections?
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Old 13th August 2003, 04:06 AM   #6
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ahhh- haaaaaaaaa!

yes, that's it. the symbol in the schematic looks like a nonpolar capacitor, except it's STRADDLING another line of the circuit. i knew that meant something...too bad i neglected to mention it. (early-onset senility.)

next question: do they need replacing if they're 40 years old? they're in an old tube radio. i'm told that certain types should not be replaced (i.e. micas and variables) because they don't go bad as easily as papers and electrolytics, and also doing so can screw up the tuning; do these fall in that category?

thanks for the answers

/andrew
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Old 13th August 2003, 08:14 AM   #7
Electrons are yellow and more is better!
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Quote:
Originally posted by faustian bargin
next question: do they need replacing if they're 40 years old? they're in an old tube radio.
Probaly not since they are made of ceramic material (yes?).
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