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Post subject: What would you do?
Posted: Mon Aug 13, 2012 2:03 pm
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Aspiring Musician
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I recently bought 10 Nos sprague atom 25uf 50v 30D electrolytics for replacement on my bandmaster reverb. Six of the ten read 31u-33uf, which is aove the 20% tolerence. Would you use them or send them back? I'm going to email the seller to see if they will replace the "bad" ones first.
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Abe

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Post subject: Re: What would you do?
Posted: Mon Aug 13, 2012 2:22 pm
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I'd be inclined to send them back for replacement or refund.

Arjay

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Post subject: Re: What would you do?
Posted: Mon Aug 13, 2012 3:19 pm
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I would send them back also, but keep in mind that your meter also has a tolerance when reading the value of the cap (or any reading for that matter) of a few % which can add or subtract to the caps value. My meter has a +/-3% tolerance in that range so a cap that is at its upper limit and is actually 30 mFd, could measure about 31-32 mFd.

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Post subject: Re: What would you do?
Posted: Mon Aug 13, 2012 6:06 pm
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SoCal, Blue is correct --- cap meters can be notorious for wide tolerances in their readings. What kind do you have?

In any event, a little too much capacitance (35mfd versus nominal 25mfd) will prolly not hurt a tube rectifier --- even in the first filter stage. As for use in a bypass stage of a cathode-tied resistor --- too much capacitance may lead to to too much bass and even "farting tones." In extreme cases.

For filtration purposes a little too much is prolly better than 20-25% too little.


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Post subject: Re: What would you do?
Posted: Mon Aug 13, 2012 9:27 pm
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Aspiring Musician
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Joined: Fri Aug 21, 2009 1:45 pm
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Location: SoCal323
Retro, Bluesky, BMW,

Thanks a bunch for the advice. I've already emailed the retailer and i am awaiting a response.

I'm looking to replace all the white Mallory caps that are tied to the cathodes of all the 12at7's and 7025's, as most of them have drifted to 35uf and above.

Bmw, I'm utilizing a Fluke 177 meter to get my readings which is accurate to +- 1.2%+2.
So in theory a 31uf reading would still be over the 20% tolerance.
Now that you mentioned it, it does begin to "fart" out when the bass setting is above 5. I also run it through a closed back 212 cab, so maybe this contributes to the problem as well.

Anyways, I think I will go ahead and await the sellers response and send them back if they don't exchange them.

Thanks again.

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