Re: Subwoofer humming

From: Jim Adney (jadney_at_vwtype3.org)
Date: 10/16/04 

Date: Fri, 15 Oct 2004 23:24:41 -0500

On Fri, 15 Oct 2004 16:24:45 +0200 "Michael Rabeno"
<mrt2@[nospam]netvision.net.il> wrote:

>Hi,
>
>Home-made 10" subwoofer unit, connected to Kenwood AV-Receiver model
>KRF-7050D. it has it's own PS and internal, DIY 2x10W amp kit.
>When i turn on the power, the unit produces a loud hum, and after about 2
>sec. the hum is quiet but still present. when i mute my receiver, the hum
>goes away, so i suspected the input is bad. the thing has proper grounding.
>i replaced the PS, as i thought it inserts hum into the system, but no good.
>after checking the amp there were some loosen electrolytic caps (cold
>solder), which i re-soldered (i have this amp for about 12 years or so). i
>soldered another electrolytic cap to the input side of the amp (100uF, 10v)
>and tested it - now the hum is gone completely, but along with the hum went
>the sound it should produce.
>
>anything else i should check? / i've done wrong ?

Did you by any chance resolder the caps while the amp was powered up,
or when the caps were still charged?

If so, you probably blew something up when you reached in there with a
grounded soldering iron.

-
-----------------------------------------------
    Jim Adney jadney@vwtype3.org
           Madison, WI 53711 USA
-----------------------------------------------

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