[Hallicrafters] New Blue disc ceramic capacitors

[Jim Liles]

Heads up regarding the new Blue disc ceramic capacitors.

If you plan to use the NPO versions, be prepared to test them or accept totally unpredictable results.  NPO traditionally indicates +/- 30 PPM.  Many of these caps test to be well beyond the traditional norm.  Many also display a significant Hysteresis effect.  That’s to say the capacity will very with temperature and not return to the same value at the original temperature.  This is a class 3 ceramic behavior not class 1 which they should be.

Also, some of the Blue class 2 and class 3 caps used for bypass and low level coupling i.e. Z5U, X7R etc have been measured to have some of the most unbelievably bazar behavior measured to date.  Point --- a Blue  .02uf cap rated at 1000v, when exposed to as little as 600v measured to have lost 90% of it’s capacity.

The days of simply measuring a capacitor from stock and installing it into a radio or instrument are history.  Check samples from the batch that you purchase if they are newly manufactured.

Kindest regards Jim K9AXN