[R-390] Re: [Collins] R-390A Filters

[mikea]

> ----- Original Message -----
> From: John KA1XC <tetrode at comcast.net>
> Date: Thursday, December 9, 2004 1:56 pm
> Subject: Re: [R-390] Re: [Collins] R-390A Filters

[snip]

> > So I'd say that the state of the filter innards in any 390A
> > is indeed a crap shoot, even in the multi-kilobuck "'museum
> > quality" radios that pop up now and then for sale. The only thing
> > I do different now is to try minimize any mechanical shocks or
> > vibration when moving or transporting a 390A, for example putting
> > it on a cushy mat or blanket when transporting one in the back
> > of a car or truck, not for the sake of the tubes but for the
> > filters.It's ironic that although the R-390 is a much older beast
> > than the average R-390A it is not as fragile in this respect.

On Thu, Dec 09, 2004 at 04:58:29PM -0500, JMILLER1706 at cfl.rr.com wrote:
> Is that because the older 390 (non A) did not use mechanical
> filters like te ones in the 390a? I have experienced a similar
> failure in an 8 khz filter but it was heat related... the filter
> worked fine until the box warmed up and then would fail. Some
> have talked about opening them up with blow torch or solder iron,
> then replacing the innards with a "new" Collins mechanical filter
> module, similar to what has been done with 75A4 filters by Curry
> Longwave. Curry also sells "modernized" filters for the 390a... see:
> http://www.r390a.com/html/Curry.html

Yes. The R-390 (non A) uses LC filters, and (IIRC) crystal filters. 

-- 
Mike Andrews
mikea at mikea.ath.cx
Tired old sysadmin