[R-390] R 390A Audio

[Bernie Doran]

One more audio option that I have started using is to clean off most of the 
Vacuum tubes and audio transformers on the module and simply mount one or 
two of the vast assortment of solid state audio chips. 12 volts provides a 
room full of audio at distortion lower that most can even measure with a 
frequency response that is way beyond anything  usable.   plus these rascals 
only cost a few bucks. one thing I have noticed is that, like most solid 
state, they do not like RF, so it may be necessary to kill the supply 
voltage to them on transmit.    And if you are green, sorry for you, but 
this does save some energy and heat. Regarding solid state in a 390, 
remember the rectifier change is pretty much accepted.   Bernie

---- Original Message ----- 
From: "Perry Sandeen" <sandeenpa at yahoo.com>
To: <r-390 at mailman.qth.net>
Sent: Wednesday, April 25, 2012 12:36 AM
Subject: [R-390] R 390A Audio and AGC


>
> GM List,
>
> No matter what brand of 600 ohm to 4/8 ohm transformer one uses, one still 
> has the same original crapola sound.
>
> There was an article titled Cheaper and Simpler Upgrades for the R-390A HF 
> Receiver by Chuck Felton  KD0ZS (Felton Electronic Design PO Box 187 
> Wheatland, WY 82201 published in Electric Radio Magazine August 2004.
>
> Among many improvements he covers are the factory audio problems.
>
> I have Chuck’s permission to redistribute his article.  If interested 
> reply off list and I’ll email a copy.
>
> There are some audio improvement mods to be found in the Y2KR3 manual 
> also.
>
> For a few dollars more (sorry Clint) for a P-P output transformer from 
> antique audio, one can do the Kleronomos  mod.  This mod can be modified 
> to use P-P 6AQ5 tubes mounted in place of the 8 pin plug in capacitors by 
> using modern replacements mounted on a terminal strip underneath the large 
> filter chokes.  Of course if one doe this one should remount the three 
> power resistors underneath the chokes to the top side of the chassis.
>
> I have a copy of that schematic also if one needs it.
>
> Regards,
>
> Perrier
>
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