[R-390] Second R-725 on ebay

David C. Hallam dhallam at rapidsys.com
Sat May 9 14:33:19 EDT 2009


The magnetic shielding properties of Mu metal are very sensitive to cold 
working such as bending, etc.  I believe Mu metal shields were annealed 
after forming to obtain maximum effect.

David
KC2JD/4

ToddRoberts2001 at aol.com wrote:
> Hi All,
> It looks like a true R-725 has a mu-metal shield added around the outside  
> of the round PTO shield
> can. Does anyone know if it really makes a difference in the performance of 
>  the PTO?
>  
> I know mu-metal shielding is added around small audio transformers to  
> reduce the 
> chance of any hum pickup. Is the R-390A PTO susceptible to hum pickup  from 
> the
> power transformer next to it on the underside of the chassis?
>  
> I see it looks like there is some kind of added transformer next to the  
> regular power
> transformer on the underside also on the R-725?
>  
> If adding a mu-metal shield is beneficial there are places that sell  
> mu-metal foil that
> one could wrap around the PTO can.
>  
> 73 Todd WD4NGG
>  
>  
>  
>  
> **************Remember Mom this Mother's Day! Find a florist near you now. 
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