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Hoffman Amps Forum image Author Topic: Capacitor Value?  (Read 2812 times)

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Offline plexi50

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Capacitor Value?
« on: October 25, 2011, 01:18:07 pm »
I have a cap that is leaking DC voltage.  What do you think is the value of the cap pictured below?  Looks like 15 nano farad but it has 500 next to it.  I am not sure. This may not be an american made cap

I am assuming it is leaking because i am getting a small voltage on the other side of it
« Last Edit: October 25, 2011, 01:26:50 pm by plexi50 »

Offline FYL

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Re: Capacitor Value?
« Reply #1 on: October 25, 2011, 02:45:33 pm »
Looks like a mica, an old poly or a weird ceramics.

There are three color bands, could be the old color code, used until the '90s or so. Yellow = 4, White = 9 if colors are correct on a ca. 1988 cap seen in quite low res on a laptop. 49 E 4 pf = 49 000 pF = 49 nF doesn't click as a standard value. Ditto if yellow isn't yellow but faded orange or brown.

So let's consider the markings. The inverted U could be a n, if so in European notation n15 = 0.15 nF = 150 pF. 500 could be the working voltage, quite strange in a silicon-based amp but pretty normal if the cap is a mica.

So I'd venture an educated guess : 0.15 nF / 500 V mica cap.

Now remove the offending cap and measure it... Even if it's leaky, you'll be able to measure it's capacitance.




Offline sluckey

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Re: Capacitor Value?
« Reply #2 on: October 25, 2011, 02:55:02 pm »
Quote
I have a cap that is leaking DC voltage
How do you know that? Have you disconnected one end of the cap and actually measured a dc voltage on the disconnected end?

Or do you simply measure a voltage on each lead of the cap? This is absolutely normal and quite common.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline plexi50

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Re: Capacitor Value?
« Reply #3 on: October 25, 2011, 04:12:06 pm »
Thanks you all. I was thinking 15 nana 500 V but better to ask. Steve i lifted one end of it off the circuit board and it is showing near 1 volt. I am thinking to hard on this Greek amplifier im dead set on fixing
« Last Edit: October 25, 2011, 06:40:44 pm by plexi50 »

Offline PRR

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Re: Capacitor Value?
« Reply #4 on: October 25, 2011, 08:37:22 pm »
It's not a tube amp. It would be quite common for there to be voltage on both sides.

stratele52

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Re: Capacitor Value?
« Reply #5 on: October 26, 2011, 03:41:41 am »
It look to be 15 nanofarad = 0.015 microfarad at  500 volts , but I don't think you need 500 volts capacitor

 


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