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I'm hoping someone can help me confirm the specs of a capacitor that blew out in my subwoofer amp and confirm an equivalent part.

I've identified the board it was mounted on as an IcePower250W amplifier (shown here). The capacitor markings were obliterated when it blew out, but from what I can tell from the picture (component C20), it's marked as (270nK MMK BAN 63-) which I think is a 0.27uF 63V MKT radial metalized film capacitor.

I believe this part might be an equivalent replacement, but I'm not entirely sure, so I'm hoping someone here can confirm both the identification and replacement.

Thanks in advance for the help!

enter image description here

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    \$\begingroup\$ what about the component failure that caused the cap to blow? \$\endgroup\$
    – jsotola
    Oct 24, 2021 at 18:27
  • \$\begingroup\$ Replace it and see; values seem plausible. Suggest higher voltage rating if it will fit. Identify the driver IC and power from a current-limited bench supply to prevent further damage if something else is still wrong (likely.) Check the speaker(s) also. \$\endgroup\$
    – rdtsc
    Oct 24, 2021 at 18:55
  • \$\begingroup\$ IF this one blew , maybe you want a better cap. The critical factor is D.F. at some switching frequency, instead of 100 parts without specs. DF of <=1% is common but could be 10% at switching f. \$\endgroup\$ Oct 24, 2021 at 19:43
  • \$\begingroup\$ Great question. I’m not entirely sure what caused it to blow out, to be honest. My first thought was that it just failed from age. However, I did find a defective resistor that I’m replacing as well as a fuse tube that blew at the same time, both in line in front of this board. There is also another film capacitor that folks who have this subwoofer say seems to go bad as well. Since I don’t have a good tester, I’m just going to replace it as well. \$\endgroup\$
    – Wraith44
    Oct 24, 2021 at 22:55

2 Answers 2

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I believe this part might be an equivalent replacement

It is, at least electrically. What we don't know is if mechanically it has the same lead spacing.

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  • \$\begingroup\$ This should be a comment, not an answer. \$\endgroup\$
    – Lundin
    Oct 25, 2021 at 13:07
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I would prefer a much lower ESR or D.F. than a random metal film cap. So choose PP type film rather than PE.

Not all are the same. Since it is near the large coil for likely a Class D/E Bass Amp, the cap is used to filter switching square waves going to bass speaker that are PWM modulated, so there will be high ripple currents. These parts have a PTC effect in the conductors like any metal so as they get warm, the resistance rises with thermal runaway.

It is much bigger, but I think you can squeeze it in with heatshrink on exposed leads and is worth the cost. enter image description here

This one is non-inductive low D.F.. Others like your Vishay/Kemet are 1% DF @ 1kHz and n/a at 10kHz and made of Polyester (PE)

Panasonic type Polypropylene (PP) is better also rated at high voltage ( no matter) but bigger.

https://www.digikey.com/en/products/detail/panasonic-electronic-components/ECW-F4274HL/656351

https://industrial.panasonic.com/cdbs/www-data/pdf/RDI0000/ABD0000C245.pdf

0.27 uF @ 400V
0.2% loss at 10 kHz
0.05% loss at 1 kHz

$1.87 (1) also more expensive each but less overall.

Plastic Film Capacitors Non-inductive construction using metallized polypropylene film with flame retardant epoxy resin coating


Perhaps equivalent, but 6x hotter at 10 kHz

A PE example from Kemet as follows is similar to what you found enter image description here https://content.kemet.com/datasheets/KEM_F3065_F611_F612.pdf

enter image description here

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    \$\begingroup\$ Wow, this is really great info. I would absolutely prefer to install something of better quality, as long as it’s electrically compatible. The heat might be a concern, as there isn’t any active cooling and it’s in a metal enclosure, but I have to admit that I’m a bit over my head here. If you think it will work, I’m down to try it. I don’t have anything to lose, since it will just get junked if I can’t fix it and it’s a fairly small investment. \$\endgroup\$
    – Wraith44
    Oct 24, 2021 at 23:19
  • \$\begingroup\$ This cap will perform better than the last at high power but I can't vouch for any other failures that may or may not exist. The large electrolytics should not have any gas pressure dome effect on the lids. \$\endgroup\$ Oct 24, 2021 at 23:34
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    \$\begingroup\$ Much appreciated, kind sir! I’ll post back to let you know know how I make out after the components arrive. \$\endgroup\$
    – Wraith44
    Oct 25, 2021 at 2:51

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