capacitor schematic label question

[faustian bargin]

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

 

[JOE DIRT®]

I`m guessing here but it could be FT= film type

 

[faustian bargin]

thanks.

sounds plausible, anyway!

/andrew

 

[dhaen]

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:

 

[peranders]

If you have the schematic I gather that the feed-through symbol doesn't look like a capaictor, more like a wire, 3 connections?

 

[faustian bargin]

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

 

[peranders]

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?).