[R-390] Another Fine Mess?

[ToddRoberts2001 at aol.com]

In a message dated 4/21/2007 4:01:15 PM Eastern Standard Time, 
wmarvin at hickorytech.net writes:
Hi All   Well I may have done a REAL DUMB thing..........while recapping the 
IF deck with orange drop caps I had no idea that the are polarized, foil 
outside (Right)......no markings
on them...........will this mistake upset tithe IF circuit????  At least I 
have a 50/50 chance
to rework..........duh !!!
 
 
I have always heard it is best to connect the outside foil of a bypass cap to 
ground. It helps to insure the circuit will be stable and prevent noise and 
hum pickup. An easy way to find the outside foil in an unmarked cap is to rig 
up a simple test fixture using an audio amp with either a line-level or mic 
input. The mic input will be more sensitive. Make up a short lead using shielded 
wire with the correct plug going to the amplifier input with the ground side 
going to the cable shield. Put clips on the other end of the cable leads and 
clip one lead to each side of the bypass cap. Hold the cap between your thumb 
and forefinger. If hum increases then the outside foil is going to the hot lead. 
If no hum increase then the outside foil is going to ground. Once you make up 
the test cable you can check the caps real fast using this method. It also 
illustrates why the outside foil should go to ground - less chance of hum or 
noise pickup.
73 Todd WD4NGG



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