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Lifespan of capacitors
Lifespan of capacitors
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Old 15th October 2018, 12:23 PM   #11
shreekumar is offline shreekumar
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Default Pls identify the capacitor manufacturer

Hello

Pls refer to the attached photos of Polyproplyne capacitor,
These were removed from a Yamaha cx1000 preamp.
Can the manufacturer be identified by its logo

Thanks
Shree
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Old 15th October 2018, 03:33 PM   #12
Vovk Z is offline Vovk Z  Ukraine
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Are you shure that they are polypropylene type?
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Old 15th October 2018, 03:52 PM   #13
sq225917 is offline sq225917  United Kingdom
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Send a message via MSN to sq225917 Lifespan of capacitors
Seem small for stated value if pp caps.
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Paradise Pre-reg PSU PCBs
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Old 15th October 2018, 04:18 PM   #14
ticknpop is offline ticknpop  Canada
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Lifespan of capacitors
they look like polyester, but if manual says their polypropelene then that's what they are,
Better to buy Wima or Panasonic now
(Panasonics with copper , not copper plated steel legs)

Last edited by ticknpop; 15th October 2018 at 04:21 PM.
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Old 15th October 2018, 05:47 PM   #15
DF96 is offline DF96  England
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My guess would be polyester. No idea about the logo. Doesn't Google have a picture search capability?
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Old 18th October 2018, 09:00 AM   #16
shreekumar is offline shreekumar
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Yes these are Polyproplyne, as mentioned in the service manual
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Old 18th October 2018, 09:04 AM   #17
shreekumar is offline shreekumar
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I have replaced these with new Wima, but still feels the older ones sound better than the Wima..the reason I changed these We're due to discoloration on the 333k and on the 104k were covered with a gummy layer.
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Old 18th October 2018, 09:06 AM   #18
shreekumar is offline shreekumar
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Tried searching on Google, couldn't come up with a similar type
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Old 21st October 2018, 11:08 PM   #19
Monte McGuire is offline Monte McGuire
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Lifespan of capacitors
You can identify a film cap dielectric by testing its dielectric absorption. You can do this in the field with a 9V battery and a basic DMM. Charge the cap by connecting it across the battery for 10 seconds, take the battery off, short the cap leads for exactly one second and then measure the voltage that appears across the cap using a high input impedance voltmeter - a modern el-cheapo 3.5 digit DMM in voltage mode is fine. Try not to touch both leads when measuring the recovery voltage - you don't want to drain off any of the recovery charge and affect the voltage reading.

The recovery voltage is not dependent on the value of the cap, only the dielectric. It's a percentage of the applied voltage, and depends only upon the dielectric composition. You'll have to get some samples of various capacitors with known dielectrics like mylar, polypropylene, polystyrene, polycarbonate, teflon etc. and apply this measurement procedure repeatably to get a set of numbers that correspond with these dielectrics. The recovery voltages are on the order of 1-10 millivolts with a 9V battery and this basic procedure. Some of the higher performing dielectrics like teflon, polystyrene and polypropylene might be hard to distinguish among, since their dielectric absorption is so low. However, polycarbonate will be a good bit higher, and mylar will be a good bit higher than mylar, so you can distinguish among the "good" dielectrics and the lesser dielectrics pretty reliably.

I've used this procedure at flea markets to determine whether to buy a box of caps or not, and it's been very useful and reasonably reliable if your procedure is consistent. It's also non-destructive, so you could easily test the parts you have and then re-use them.
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