Replacing old capacitors


Posted on Feb 6, 2014

Original components, when still good, are stable and not subjected to infant mortality. Of course everybody has his own opinions derived from past experiences. Nevertheless answers may vary depending upon several reasons: quality of the design with proper use of right components, type and quality of materials, environmental conditions


Replacing old capacitors
Click here to download the full size of the above Circuit.

during life and storage of equipment. I see frequent discussions tied to specific models. Since almost every collector of old radio equipment may be interested in this topic, I decided to open a generic thread, hoping that readers would add their experiences. A short can be easily identified by low voltage and/or resistance values all around the faulty section. Often shorted caps cause other faults, as burned resistors or blown fuses. Whenever one of the latter conditions is encountered, shorted capacitor should be suspected unless different cause is found. This failure is common in electrolytic capacitors, when fully dried. If faulty capacitor is in the B+ filter section, a loud hum will arise. In some circumstances, such as in the cathode path of audio power amplifier tubes, a dried capacitor could also give benefic effect on sound quality. Opens can also be occasionally found in some polystyrene foil capacitors, due thermal stress on the leads. These may derive from different causes: partial drying of electrolyte in aluminum capacitors; drying or alteration of impregnating oils or waxes in paper capacitors; moisture adsorption in ceramic or in paper dielectric; small cracks in silver coating of some lacquered mica capacitors, partial chipping of ceramic capacitors. A twenty-percent decrease in the capacitance of filter electrolytic capacitors may be tolerated, but a five-percent variation on the value of ceramic...




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    FM stereo multiplex generator
    Musical telephone ringer
    Sine- And Square-Wave Ttl Oscillator
    AD9284 default mode problem
    vackar vfo oscillator
    50w audio amplifier using ic tda1562
    cool chip lt1970 power op amp with current limit
    pic icsp
    Voltage doubler circuit using NE555
    LM231 Precision Voltage-to-Frequency Converter
    Whistle Light Switch
    Multi-Colour LED
    MD1 audio w/ mCD & 32x buffer amp circuit
    AP500 and its application circuit ab



    Top