[R-390] EAC power hum

[Joe Foley]

Put washers under the transformer at the green screw locations.  That will lift the transformer away from the chassis.  As per Nolan Lee.

Joe





--- On Fri, 1/8/10, Les Locklear <leslocklear at cableone.net> wrote:

> From: Les Locklear <leslocklear at cableone.net>
> Subject: Re: [R-390] EAC power hum
> To: "Steve Toth" <stoth47 at yahoo.com>, r-390 at mailman.qth.net
> Date: Friday, January 8, 2010, 3:57 PM
> EAC Power Supplies (bot all ef them)
> have a well documented mechanical hum. Insulate the hold
> down screws, or leave them loose. Short of anything else,
> replace it.
> 
> YMMV
> 
> Les Locklear
> Gulfport, Ms.
> Dx'ing since '57
> 
> 
>   ----- Original Message ----- 
>   From: Steve Toth 
>   To: r-390 at mailman.qth.net
> 
>   Sent: Friday, January 08, 2010 12:24 PM
>   Subject: [R-390] EAC power hum
> 
> 
>   Just powered up a late model EAC I purchased and it
> has a loud mechanical hum when cold. It's a complete EAC
> with all EAC decks. I compared it with my Collins and
> Motorola and it is much louder than either one.
> 
>   I looked through the "Pearls" and used an insulated
> screwdriver to listen to components and the hum seems to be
> coming from the transformer (to a lesser extent) and the
> line power filter (to a greater extent). The 25Z5's both
> check good on the TV-7 with no shorts. I haven't checked the
> rest of the tubes yet. I also haven't swapped the power deck
> from either of the other receivers yet. 
> 
>   I loosened up the six power supply mounting screws
> and that did seem to decrease the hum level to an almost
> acceptable level by apparently reducing the sound conduction
> from the power supply to the chassis, but I'm not real keen
> on the idea of leaving the mounting screws loose.
> 
>   What has been found to be an acceptable way of
> decreasing the sound conductivity and retaining the mounting
> and grounding integrity on the power supply?
> 
>   I would like to keep all the decks EAC. What has the
> group decided is the best cure? IEC approved line filter?
> (don't flame me on that one) Different power supply module?
> Replace the power transformer? 
> 
>   Or, just live with it - Hey!, it's an EAC! .
> 
> 
> 
> 
> 
> 
> 
>   -- Steve 
>   Woodinville, WA
> 
> 
> 
> 
>         
>  
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