Fw: [R-390]

[Dan Merz]

Lee,  I haven't tried the 6aq5 audio mod in the recent ER but it looks
interesting and should be an improvement.  I completed the earlier mod mentioned
in the article which put a push-pull 6360 tube (twin tetrode)  as output tube in
place of one of the tubes,  also an ER article.  This was somewhat more
complicated and works very well and is less likely to saturate the core of the
small audio transformer that can fit on the chassis.  I was a little surprised
the recent author didn't do some sort of comparison or even mention why he
didn't go with the earlier 6360 mod,  but I'm guessing it was because his mod is
easier to do (doesn't require changing a tube socket).  His article did have the
word SIMPLE in the title !!  And maybe he thought a 6aq5 should be used because
after all it's an audio tube whereas a 6360 is a vhf transmitter tube.   I
bought a second audio chassis for the mod but I haven't put my original chassis
back in since - the audio is very good.  Maybe the next owner will want the
original so that is why I kept the chassis I got with the set in its original
state.  best regards,   Dan

Lee Bahr wrote:

> I went to the Arlington Ham Comm in Texas yesterday and bought my third
> R-390A.  It was a Motorola, serial # 1587.  All meters are intact but the
> chap who sold it to me for $250 said it does not work on all bands and he
> didn't  know what was wrong with it. He said he found it in a corporation's
> disposable pile.  Now I have 3 of them to restore!  (The other two are EAS
> units).  The Motorola unit looks clean and the front panel is nice but not
> perfect.  All the covers are there.
>
> What would be the most logical reason for some bands not working?  I guess
> crystals would be suspect and maybe switch contacts, if nobody was screwing
> slugs around in the unit.  (I'll check to see if rack coil slugs are
> moving).
>
> Also, what do you guys think of the latest Electric Radio's article (June,
> 2004) on improving R-390A audio?  I'm thinking of trying this if I ever/when
> get my radios up and running,
>
> I just ordered the two sets of Hi-Res videos on the R-390A as well as the
> set for the SP-600JX but they have not arrived from Hi-Res as yet.  My two
> cap kits for my first two R390As have been sitting on the work bench for
> weeks now.  Maybe the videos will get me going!
>
> Lee, w0vt
> Houston
>
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