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DIY Stompboxes => Building your own stompbox => Topic started by: powerplayj on August 20, 2006, 02:01:59 PM

Title: should I have continuity across a capacitor?
Post by: powerplayj on August 20, 2006, 02:01:59 PM
I was troubleshooting my EA Tremolo for solder bridges and noticed there was continuity across a 22uf electrolytic (16V) cap.  Is there ever a case when this should happen?  The two legs are on different solder pads and the cap is in series between a FET and a resistor.  See C3 below.

http://www.generalguitargadgets.com/diagrams/eatrem2_lo.gif
Title: Re: should I have continuity across a capacitor?
Post by: DuncanM on August 20, 2006, 02:19:33 PM
Difficult to tell "in circuit" - the capacitor should start out looking short circuit and then as it charges (from the meter) the resistance would rise until it appears "open circuit".
However, in this instance the charge could leak away through the 1.2k resistor in series with the D-S resistance of the FET.
So continuity might be indicated.

If in doubt, I'd pull the cap and test it out of the circuit.
Title: Re: should I have continuity across a capacitor?
Post by: Peter Snowberg on August 20, 2006, 02:52:28 PM
If the transistor conducts anything, you'll see a reading on the meter beause there will be an aternate path for the power used in checking to flow.

Just about any electrolytic will look like a short when it has no power stored in it. As the voltage in the cap rises, the continuity reading on the meter will get weaker and eventually the meter may stop showing continuity.

Caps are just hard to test in-circuit.