diode and capacitor polarity question

[jertub]

Hi-

Please see photo.

Is the tapered end (left) of the diodes the anode (+) or the cathode (-)?
Is the side of the capacitor with the yellow band positive or negative?

Thanks
Jerry

 

[knockbill]

Tapered end is positive,,, band on the cap indicates the foil end, cap is non polarized...

 

[gadget73]

If in doubt about the diodes, confirm it with your meter. Honestly silicon diodes rarely go bad, so you may not need to change them. I seldom do in old gear unless I break the the leads trying to remove other parts from the terminal.

+1 outer foil.

 

[jertub]

Thanks Knockbill for the reply. When you say foil end I assume that has something to do with shielding in some applications.

 

[jertub]

My rational for changing the diodes is because I would have to desolder that terminal strip to get at the capacitor anyhow. And the leads look burned to me?

 

[avionic]

And the leads look burned to me?

not burned -- silver plate tarnish/oxidation

 

[gadget73]

Kind-of shielding. Capacitors are basically two strips of aluminum foil with a piece of paper between them, all rolled up and jammed into a tube. The outer foil is simply the foil that is closest to the outside of the tube. In some really cranky circuits, it can be helpful to put that towards the ground side to help shield from noise. Modern caps aren't marked for this, but you can figure it out with a scope or an audio amp. Basically you hook the thing up and whichever way produces more hum while you hold the cap in your fingers, the + lead of the amp or scope is connected to the outer foil.

and yeah, silver oxide on the leads.

 

[jertub]

Tapered end is positive,,, band on the cap indicates the foil end, cap is non polarized...

Are you sure about the tapered end being positive?

Havent had a chance to get at those diodes with a meter, just trying to map it out in my head until i do.

 

[knockbill]

If in doubt, confirm with DMM...

 

[jertub]

Tapered end is positive,,, ...

For the record the above statement is false.

The tapered end is the cathode (negative).

 

[triode17]

For the record the above statement is false.

The tapered end is the cathode (negative).

I think you mean that the tapered end is where your neg. meter lead went to turn the diode on. With the pos. meter lead on the round end and the neg. lead on the tapered end turned it on, the tapered end IS the cathode which goes to the positive side of the capacitor. Be careful about this polarity or the caps. may explode when you power up the amp. That's why I always use a Variac and monitor the input power using a Kill-A Watt. If it starts rising quickly as you turn the Variac, you've done something wrong.

 

[jertub]