Bumble Bee capacitors

A variety of capacitors known as Black Beauty or Bumble Bee are found in much of the classic Tek gear. Some, not all, of these capacitors age very poorly, including shorting out, which can harm the surrounding components in a circuit. Many experts recommend replacing all Black Beauties with modern capacitors. Modern equivalents are not a problem to find.

If one does not wish to replace the old capacitors, testing them is an option. There are three main ways that capacitors go bad.

• The capacitor can leak DC (or short completely).
• The capacitor can drift significantly in capacitance.
• The capacitor's equivalent series resistance (ESR) can increase significantly.

Each of these problems can be checked for using basic test equipment. It is time-consuming, but if, for example, one is determined to keep an instrument as original as possible, the following procedure will find most of problems with black beauty capacitors.

1) Remove one end of the capacitor from the surrounding circuit.

2) Check for DC leakage: To do this, you will need a DC power supply that has current limiting and goes up to the operating voltage of the capacitor. Disconnect one end of the capacitor. Attach an sensitive ammeter in series with the power supply and the capacitor, and bring the power supply up to operating voltage of the capacitor.

3) Check for drift in capacitance: Discharge the capacitor. Measure it with a capacitance meter.

4) Measure the ESR: (to be continued)