[R-390] Hello

[Bob Camp]

Hi

Congratulations on getting some "real" radios.

You may want to take a look at

http://www.hausernet.com/r390a/

For a copy of the Y2K version of the R390A manual. It is posted on 
Barry's site and he's a regular here on the list. There are also 
scanned copies of most of the military manuals available for download 
at various places on the net.

You might also want to check out

http://www.r390a.com/

as a good starting point for a lot of R-390 information.

I would not worry about finding any 26Z5's. The military started 
replacing them with solid state diodes quite a while back. These days 
there isn't a lot of price difference between low voltage and high 
voltage diodes so I would go with 1KV rated diodes. The same applies to 
the cost of low current versus high current diodes. I would go for 
something like 3 amp parts. Both of those ratings are overkill but the 
25 cent price difference probably won't impact your lifestyle to 
severely.

The whole carrier meter calibration thing gets a bit involved. The 
radios probably need a full alignment if they have been in storage for 
a while. As part of the process you set the carrier meters up so they 
agree with each other. A signal generator is pretty useful for this 
process. The IF gain is also set as part of this process and that also 
affects the radio quite a bit. There are differing opinions on the best 
setting of the IF gain.

One nice thing about having a pair of radios is that you can swap 
modules between them if you suspect a problem. This makes the whole 
maintenance process a whole lot easier. For example you might have a 
leaky capacitor on your agc line. That line runs all over the place. 
It's nice to be able to swap out the IF deck to isolate the general 
location of the problem before you tear into the RF deck.

I'm sure some of that doesn't make a lot of sense right now, but 
hopefully it will as you dig into the radios.

Don't be afraid to work on these beasts. They were designed to be 
maintained and aligned by your average joe. They are tube based so they 
will require a bit more tender loving care than a solid state radio. 
That said, they are well worth the effort.

	Enjoy!

		Bob Camp
		KB8TQ




On Jul 30, 2004, at 4:02 PM, Mike Wells wrote:

> I am new to the list. I just picked up a couple R-390A's last week and
> thought I would see what sort of helpful pointers I could get. The 
> receivers
> I picked up are nice units. One is a Collins built unit and the other 
> is a
> Capehart unit.
>
> I'm sure that there has been lots of chatter about the 26Z5 rectifier 
> tubes.
> I am in need of one and started looking around and it appears they may 
> be
> hard to find and expensive. Is there a good source for them?
>
> I am also curious about the calibration of the carrier level meter. I 
> have
> adjusted the zero set point, however with the two 390's setting side 
> by side
> one registers a much higher reading on the same signal, yet they both 
> hear
> very well. Guess that only listening by ear isn't a good sample so 
> would you
> think its just an alignment problem?
>
> Thanks
> Mike W0FD
>
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