Mallory 150s Outer Foil

[VibroMan]

Does anyone know if the Mallory 150 series have the outer foil marked?

[RussB]

no, they do not

[Trout]

Originally Posted by VibroMan

Does anyone know if the Mallory 150 series have the outer foil marked?

They are not marked, however, you can easily make a very simple tester to determine proper orientation

Outer Film Tester

[Baxtercat]

BTW: which way does the foil go on, say a Fender grommet board? I see the bar [foil] going up to ground [towards the pots] on many tone and coupling caps, but sometimes see the bar going down on blue moldeds in some of my Fenders.

[andrekp]

Can't you wrap some foil around the outside of the cap, then measure capacitance between one lead and the other to that foil wrap and you can tell which side was the outside lead from the capacitance value?

makes perfect sense anyway.

Thought I saw that somewhere once.

[AL30]

Originally Posted by Baxtercat

BTW: which way does the foil go on, say a Fender grommet board? I see the bar [foil] going up to ground [towards the pots] on many tone and coupling caps, but sometimes see the bar going down on blue moldeds in some of my Fenders.

They're not polarized caps. They'll work just fine in any direction.

AL

[John Ward]

They work in either direction, but may be quieter in one direction.
Randall Aiken has a good explanation:
http://www.aikenamps.com/OutsideFoil.htm
And there is a good Youtube video showing how to test which end of a non-polarized cap has the outside foil.
http://www.youtube.com/watch?v=VP6ZIHXq6Yg OK, I just noticed that Trout already answered with a link to this video. If you have a scope, the test is easy.

[Baxtercat]

Ahh, it's mostly the shielding for slight noise reduction [I figured they were bi-directional]. Well, I won't sweat it then: most the clubs hum and buzz so much anyway.

[Baxtercat]

Here it is plain and simple. Three situations:

The proper way to connect the outside foil is to the low impedance side of the circuit, which, in the case of coupling caps, will normally be the plate of the previous stage. If it is a bypass cap to ground, connect the outside foil to the grounded side. If it is a bypass cap from a signal to B+, connect the outside foil to B+. The outside foil will act as a shield against electric field coupling into the capacitor, so you want it to have the lowest impedance return path to ground.


Thxx all