[Boatanchors] Ranger Caps and Solid State Rectifiers

[Carl]

>  Never mess with mica caps !

I strongly disagree. From the 30's to the 70's micas are failing at a 
regular rate. I have to replace them in ham, commercial, consumer radios 
and test equipment regularly.


>  Please !  Forget  using solid state rectifiers in tube radios.  They 
> will ruin your tubes by stripping the filaments during warm up


Pure mythology with no basis in reality. For almost 20 years SS 
rectifiers were used in all sorts of electronics with many of the same 
tubes that used tube rectifiers earlier. Many of the same model made the 
switch during a production run.

... and the voltages will all run too high.


Maybe, I cant speak to a Ranger but a lot depends upon the rectifier 
tube and the current draw to determine the rectifier tube drop from the 
manufacturers curves.



----- Original Message ----- 
From: "Bob Sullivan" <robert at isquare.com>
To: "BLIMPY" <blimpboy at sonic.net>
Cc: <boatanchors at mailman.qth.net>
Sent: Monday, October 13, 2008 8:16 PM
Subject: Re: [Boatanchors] Ranger Caps and Solid State Rectifiers


Larry,

With all due respect, one needs to look at the old micas! They
frequently become leaky especially if they see DC (I think this is a
migration issue). I've replaced so many during troubleshooting that I
now replace all micas used as coupling caps - just to save grief later.

73, Bob
WØYVA
http://www.isquare.com/personal_pages/ras-hardware.htm

On Oct 13, 2008, at 6:46 PM, BLIMPY wrote:

>
> 1. Yup, those turquoise caps are old plastic molded paper caps.. and
> like all old paper caps... they have to go !
>
>   Suitable replacements for paper caps are either polyethelene,
> mylar or polyester.   Some hi-fi purists insist on polyester.  They
> cost a few cents more.. and for a radio that sounds a good as the
> ranger why not... but again only for the coupling caps.  Bypass caps
> needn't be fancy. Use the nice yellow japanese ones sold by Antique
> Electronics Supply or Radio Daze.
>
>  Old electrolytics must go !.  Leave those mounted on the chassis
> for cosmetic reasons, but use nice new jap caps underneath.
>
>  Never mess with mica caps !
>
>   Please !  Forget  using solid state rectifiers in tube radios.
> They will ruin your tubes by stripping the filaments during warm
> up... and the voltages will all run too high.  Any kind of voltage "
> sag" was figured into the original design specs by the engineers at
> Johnson.
>
>   There is no heat problem with a ranger or any of the other
> commercially made ham AM transmitters, anyway. Don't fix engineering
> problems that don't exist, is my advice.   If you really want "
> coolth"   buy a muffin fan.  A 220v muffin fan run on 110v  runs
> quiet.  put 4 stick on grommet type feet on it.. and go to town.
>
> Larry
> _______________________________________________
>




--------------------------------------------------------------------------------


> _______________________________________________
>