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Author Topic: Advice on replacing capacitors  (Read 902 times)

Stephen Kirby

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Re: Advice on replacing capacitors
« Reply #10 on: November 09, 2018, 12:38:48 am »

When replacing PS filtering in lower rail things like a DBX noise gate do you have to voltage limit the initial power up like you do with a 450v tube amp?  I don't have a variac but somewhere in the garage I have a setup with a lamp socket in series.  As the caps take their initial charge you can see the brightness of the lamp change.
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Frank Koenig

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Re: Advice on replacing capacitors
« Reply #11 on: November 09, 2018, 11:16:34 am »

When replacing PS filtering in lower rail things like a DBX noise gate do you have to voltage limit the initial power up like you do with a 450v tube amp?  I don't have a variac but somewhere in the garage I have a setup with a lamp socket in series.  As the caps take their initial charge you can see the brightness of the lamp change.

Don't worry about it. When the gear was built they soldered in the caps and turned on the power. The advice to bring the voltage up slowly on big electrolytic caps applies to antique gear that's been sitting unpowered for decades, and might not matter even in that case. JR, others, what do you think? -F
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John Roberts {JR}

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Re: Advice on replacing capacitors
« Reply #12 on: November 09, 2018, 11:21:33 am »

When replacing PS filtering in lower rail things like a DBX noise gate do you have to voltage limit the initial power up like you do with a 450v tube amp?  I don't have a variac but somewhere in the garage I have a setup with a lamp socket in series.  As the caps take their initial charge you can see the brightness of the lamp change.
No... new electrolytic caps come already formed, ready to fire up with rated voltage.

In 15 years at peavey I experienced one batch of noisy DC blocking caps. In hindsight I suspect they were no properly formed in by the capacitor manufacturer.

JR
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Joseph D. Macry

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Re: Advice on replacing capacitors
« Reply #13 on: November 14, 2018, 08:13:32 am »

You might keep an eye out for tantalum caps - they tend to be spherical blobs, and can dry out over time like electrolytics.

Good catch, Scott. I found a tantalum cap that is shorted out (1.2 ohms on DC ohmmeter), causing the +15VDC rail to ground out.
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Joseph Macry, CTS-I
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Ivan Beaver

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Re: Advice on replacing capacitors
« Reply #14 on: November 14, 2018, 12:42:15 pm »

Good catch, Scott. I found a tantalum cap that is shorted out (1.2 ohms on DC ohmmeter), causing the +15VDC rail to ground out.
Tantalums are bad for shorting out

I have replaced MANY in various consoles over the years
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Ivan Beaver
Danley Sound Labs

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