[bridkarl]

I’m having to replace this audio coupling cap between the plate of a 6F6 and a phone jack.
The parts list just says .005 20 percent mica which I’m reading as 5000pf. Am I reading that right.

Previous owner put in an .005 electrolytic.

[HowardWoodard]

According to AI, "Yes, you're reading that correctly. A .005 capacitor typically refers to 0.005 microfarads (µF), which is equivalent to 5000 picofarads (pF). The 20 percent mica notation indicates the tolerance of the capacitor, meaning its actual capacitance could vary by ±20%.

Mica capacitors are known for their stability and reliability, making them a solid choice for audio applications. If you're replacing the coupling capacitor, just ensure the voltage rating matches or exceeds the original spec.".

[bridkarl]

That’s what I thought, but when I’m undoing 50 years of “repairs” it never hurts to check. Thanks

[DaleHCook]

Why are you having to replace it? Does it measure out of tolerance? Is it mechanically damaged?

[HowardWoodard]

Not trying to answer for the OP, just commenting on the thread.

According to AI... ...assuming the electrolytic that's in it now is polarized...
--------------------------------------
Using a polarized electrolytic capacitor instead of a non-polarized one for audio coupling can lead to several issues:

- Distortion & Nonlinear Behavior – Electrolytic capacitors are designed for DC circuits, meaning they expect a constant polarity. In an AC audio signal, the voltage can reverse, causing the capacitor to behave unpredictably, introducing distortion.

- Leakage Current & Reduced Performance – Polarized electrolytic capacitors tend to have higher leakage currents, which can degrade the signal quality and reduce fidelity.

- Potential Damage – If the capacitor is reverse-biased, it may break down over time or even fail catastrophically.

- Workarounds – Some designs use two polarized electrolytic capacitors in series (with opposite polarity) to mimic a non-polarized capacitor, but this is not always ideal.

For audio applications, it's generally best to use non-polarized capacitors, such as film capacitors, which offer better frequency response and lower distortion. If space constraints require electrolytics, consider non-polarized electrolytic capacitors, which are specifically designed for AC signals.