[Milsurplus] RadioMarine Corporation AR-8506-B Receiver Resurrected.

[MICHAEL BITTNER]

Every receiver I've worked on has one of these capacitors either across the output transformer primary or from output tube plate to ground.  Radios that don't have one of these capacitors are the exception. The "across the primary" connection puts less stress on the capacitor than the other way.  Typically .001 to .006 uF and sometimes in series with a rheostat.  It serves as a tone control.  Without the rheostat, it's a fixed tone control for reducing the tinee (sp?)  high frequency sounds from radios with small speakers or other radios that require less emphasis on treble for better equalization with base.  Mike, W6MAB

> On May 2, 2022 at 11:36 PM David Stinson <arc5 at ix.netcom.com> wrote:
> 
>     WWII "Liberty Ship" RmCA AR-8506-B receiver
>     gets back to work.  This one was challenging.
>     (Got it going, Doug! TNX OM)
>     Still need to finish alignment.
> 
>     Video:
> 
>     https://photos.app.goo.gl/KqWcYNnnFaKxkj5n8
> 
>     Question:
>     I probably should know this, but I don't want
>     to assume.  Can someone please tell me
>     the purpose of the capacitor across the
>     Audio Output transformer primary?
>     C-141 from plate to screen of the 25L6.
> 
>     https://photos.app.goo.gl/BFyqarNgQ9BuQfbF7
> 
>     If it's included, or even reduced from .005
>     to .001, the Audio Output breaks into
>     "motor boat" oscillation. Lower value gives
>     slower reflex oscillation, but remove it
>     completely and it goes away. 
>     The coupling and bypass caps
>     have been replaced, as have the power supply
>     filter caps of course.  Addition of more
>     bypassing on the B+ buss has no effect.
>     The bad resistors also replaced,
>     so the grid isn't floating.
> 
>     Hints and Kinks about this rig
>     if anyone is interested.
> 
>     GL OM ES 73 DE Dave AB5S
> 
> 
> 
> 
>     ---------------------------------------------
>     [Avast logo] https://www.avast.com/antivirus 	
> 
>     This email has been checked for viruses by Avast antivirus software.
>     www.avast.com https://www.avast.com/antivirus
> 
> 




> ______________________________________________________________
>     Milsurplus mailing list
>     Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>     Help: http://mailman.qth.net/mmfaq.htm
>     Post: mailto:Milsurplus at mailman.qth.net
> 
>     This list hosted by: http://www.qsl.net
>     Please help support this email list: http://www.qsl.net/donate.html
> 



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20220503/d2df052b/attachment-0001.html>