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Oil filled coupling caps are often bad news with one excepetion

Posted by Ralph (M) on January 28, 2025 at 13:40:47

In Reply to: RE: Question about Sprague Vitamin Q posted by SuperB on January 28, 2025 at 12:42:45:

which is the ODAM part from VH Audio.

I've seen oil filled parts of various kinds (paper and even Teflon) develop electrical leakage (and I've seen a few simply leak too). The electrical leakage appears as a slight Voltage on the output of the cap that you wouldn't expect to see and might have you chasing other things like grid current in a tube or some such- a mystery Voltage.

The link below is exactly such a problem.

If such parts were installed in an output section it would be no surprise if the power tubes and/or power transformer failed. IOW they can throw off the bias (of course if you checked the bias you might find there's a problem and so avoid such consequences).

Reliability is why I personally feel its a good idea to stay away from such parts.

An oil filled part as shown in the original post is sort of thing you might use for motor run or motor start capacitor. They have a 'self healing' aspect where if they arc internally they can recover if given time. This is helpful in motor start applications.

• https://www.audioasylum.com/forums/tubediy/messages/28/28389   (Open in New Window)

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