[R-390] R-390A mounting position

[Scott, Barry (Clyde B)]

So you could mount it upside-down without introducing extra wear?

Barry(III) - N4BUQ
<g>

> Hi Joe &  List
> 
> May not be such a good idea to operate an R-390 at 45 
> degrees, or even a
> smaller angle.
> 
> The mechanics -- particularly slug racks, cam followers and the slugs
> themselves -- may rub against rear mating surfaces or pull at 
> a slight angle
> vs. full vertical position.  This may also contribute to a slight
> misalignment of gear shafts as they will tend to shift rearwards, etc.
> Parts will also mesh or ride somewhat off the wear-in positions.
> 
> For example, the slug racks have some fore-aft play and will 
> shift rearward.
> The back surfaces of the racks (with the cam followers) will 
> tend to rub up
> against the inside surface of the RF deck.  With a slight 
> shift, the slugs
> themselves will not longer be perfectly aligned with the cores and the
> support springs ("springy thingies" hanging from the racks) 
> may pull at an
> slight angle to the cores.  You could correct some of this by 
> tweaking the
> lateral slug adusters -- if it is an R-390A.  If it's an 
> R-390, there are no
> adjusters.  The increased drag might be enough to feel when 
> tuning - or
> maybe not.
> 
> In addition, it's unwise to support the radio by the front 
> panel in that
> position, so you 'd have to find a way to support it from the 
> back at that
> angle.  There also may be some tubes that should be operated 
> in a vertical
> position.  Can't say whether that would adversely affect 
> convection cooling
> at 45 degrees vs. full vertical.
> 
> Again, doesn't sound like a good idea to me.  You can 
> temporarily prop it up
> and see if there's any immediate increase in drag that way -- 
> particularly
> when turning the KC knob. Worst-case -- might even be some jamming or
> sticking slugs whereby a slug rack doesn't come down all the 
> way even with
> the return springs because the works are cocked   Even if 
> not, it's probably
> not a good move from a wear and tear standpoint.
> 
> My 2 cents submitted above.
> 
> Barry