[R-390] re; Vitamin Q caps

[wli]

Made by Sprague, my understanding is that Vitamin Q's are *paper* caps employing metallized paper with a propietary polymer (Vitamin Q) as a dielectric. They are supposedly good up to 125 degees C. They are hermetically sealed in metal cylinders with glass ends. I have done some spot checks, and NONE of mine leaked. However, my test sample is small being under 100 units tested.

I use Sprague Orange Drops as my reference data point insofar as leakage is concerned... comparing any other cap to them. The method I use is to place a VTVM in series with a 300VDC supply and the cap in question (eloquently described by Dr Jerry back in 1998 to us) looking for a reading of under 1.0v. Theoretically, a perfect capacitor with infinite resistance would give a VTVM reading of zero.

The BBOD's are also *paper*. With one exception, all of us on the list have seen these fail wholesale either thru body fractures, or significant electrical leakage on testing, so replacing all the BBOD's is highly recommended.

There is a section in Pearls that deal with caps in the R-390A exhaustively. 

W. Li