Can I use polyester caps to replace polypropylene caps in my Nakamichi 480z?

[Redkarter]

Hello all, I've found a shorted capacitor in my nakamichi 480z bias oscillator circuit. I scrounged through some of my parts units and found 2 4700pf green polyester or mylar caps that look to be the equivalent of the original 100v 4700pf orange polypropylene ones.

I am curious if I would be okay to use these to test or even a permanent replacement.

 

[spark1]

The polypropylene versions are widely considered to have better performance qualities. But the mylar are absolutely ok for testing, and depending on your level of obsessiveness, will almost assuredly be fine for long term use as well. If your boards and solder pads are fragile, not desoldering and resoldering a 2nd time may well outweigh any performance difference between a mylar and polypropylene cap.

 

[WernerO]

Mylar won't hurt at all in a bias circuit. You want PP film in audio circuits, though.

 

[gadget73]

^^ agree, for what its doing I doubt it matters much.

 

[Redkarter]

Thank you all! Very much appreciate the input!

 

[egellings]

The polypropylene versions are widely considered to have better performance qualities. But the mylar are absolutely ok for testing, and depending on your level of obsessiveness, will almost assuredly be fine for long term use as well. If your boards and solder pads are fragile, not desoldering and resoldering a 2nd time may well outweigh any performance difference between a mylar and polypropylene cap.

PPN caps have less dielectric charge absorption than the polyester ones do, and in an audio setting that is not an issue. If the cap were used in an integrator circuit used in a lab setting to capture a voltage and hold it (sample & hold) for later reading, such as in an integrator circuit, then DA could have an effect.

 

[radiokom]

PPN caps have less dielectric charge absorption than the polyester ones do, and in an audio setting that is not an issue. If the cap were used in an integrator circuit used in a lab setting to capture a voltage and hold it (sample & hold) for later reading, such as in an integrator circuit, then DA could have an effect.

I never hesitate to use polyester instead polypropylene if I do not have particular PPN nominal. Tape decks has no circuits where difference is measurable (or audible ).

 

[egellings]

I never hesitate to use polyester instead polypropylene if I do not have particular PPN nominal. Tape decks has no circuits where difference is measurable (or audible ).

For passing AC signals, the differences in the 2 dielectrics' performance will be microscopic, if even that much.

 

[nakmandan]

PE caps are fine in the bias OSC circuit. Nakamichi actually used PE caps in the older models before switching over to PP. Just try to find two of near equal capacitance, as many general purpose PE caps are 5 or 10% tolerance. But they'll still work.

 

[Redkarter]

Thanks all, they measured right around 4600pf and once installed restored the erase/record function.

 

[Krešo]

You can but anal reasoning is pushing towards the PP ones! Just like so many fellow members here... ;-)