Capacitor Replacements and Tolerance Values

[Bskitter]

Hi Guys,

I am replacing some Caps on an old Kenwood Amplifier,

I tested the main smoothing caps after the rectifier, they are rated at 6800 uf, 3 of the 4 are around this value, the 4th on is at about 6200 uf, should this cap be replaced ?

Secondly I am replacing some Ceramic Caps @ 0.01 uf, now the ones on the board are a lot bigger than the same caps you get today, is it some new process that made these caps smaller or is their voltage rating higher than the standard one ?

These caps are also near the rectifier and the RMS output by the TF is 30 Volts.

On the parts sheet it says

Ceramic 0.01uf +100% -0%.

I do not understand the percantages, could some please explain what they mean ?

The same goes for other caps I am replacing,

Mylar 0.15uf +-10%,

The percentage rating here is more understandable since it seems like the tolerance rating of that cap but +100 - 0% is confusing.

Regards

Byron

[wraper]

Most of the electrolytic capacitors have +/- 20% tolerance. Large capacitors often have +80 / -20% tolerance.
so 6200 uF should be well within the tolerance. FIY measuring capacitance will thell that something wrong with the capacitance only if capacitor is completely dead. You need ESR meter or LCR meter with ESR measurment to check if they are fine. Also, if you are using multimeter for electrolytic capacitor measurments, results won't be precise. Multimeters measure capacitors by not standardized way (LCR meters measure capacitance at particular frequency, the same way as capacitor datasheets specify), therefore parasitic effects in electrolytic capacitors will affect the measurements a lot.

Ceramic 0.01uf +100% -0%.

Means what it says. Capacitance value can be up to twice of the written.

[P90]

Replace those electrolytics with good name brand caps, make sure you don't get fakes on ebay...

[tggzzz]

Ceramic 0.01uf +100% -0%.

Means what it says. Capacitance value can be up to twice of the written.

Caution: the dielectric is important. For X7R and Y5U dielectrics, the capacitance can fall to only 20% (!) of the stated value when a DC voltage is applied. (I wonder if they could be used in place of a varicap diode?)

Many manufacturers don't define this clearly, the better ones do. See, for example https://product.tdk.com/en/search/capacitor/ceramic/mlcc/info?part_no=C1005X7R1H103K050BE

Some claim that Murata are the least bad in this respect; I have no opinion.