[R-390] R390 progress

[Flowertime01 at wmconnect.com]

Dan,

The 6AK5 is used in the R390/A it is also a 5654. I do not remember what 
belongs in the R390 for mixer tubes.

I really hate to send you into the RF deck. Not the first task to take on as 
a new R390 owner. But it sounds as if you need to get a look under there. Read 
up on the band switch adjustments, and how to set the receiver up on blocks 
to get the front panel off. Locate your green gear. (You did not hear it from 
me, but you can do a RF deck pull on the R390 without a green gear. It is of 
course easier with the gear than without by some margin or the military would 
not have spent the money on the gear)

R390s tune in bands. (.5-1) (2-3) (4-7) (8-15) (16-31) If 4, 5, 6, and 7 are 
not sounding good you must suspect the RF alignment. As you have a cal tone on 
every 100 Hkz you know the crystal oscillators are good. They could be better 
maybe, but they are at least not dead.

Since you tweaked the RF bank for the 4, 5, 6, 7 band and did not get these 
bands
to sound as good as some other bands, you need to do two things. You may have 
done them and just not reported it. Check the mechanical cam alignment at 
7.000+.
Lift the slug rack for the band and make sure the slugs are all there.

You could have a the cam miss aligned for the band.
A slug may be broken and the bottom of it setting in the coil tube.
This could have happened in shipping the receiver to its new home with you.
Look at the color dots on the slugs in the 4-8 slug rack.
One of the slugs could be the wrong part. (mechanical size is OK but materiel 
is wrong) The 4-8 band could have had a wrong slug in it for a long time.

While your at it, loosen the adjustment plate and let the slugs recenter 
while the slugs are as far down in the coil as they go (bottom of the cam). You 
will need some pointy nose pliers to undo the slug rack springs. Undo the 
springs from the rack while the rack is at the bottom of the cam. You way want to 
just watch the cam and slugs travel in the coils while you move through the MC 
bands. the racks will bind in the slide ways and not follow tightly on the cam. 
This will give you weak signals.

All cal tones on all bands will not have equal strength. Weak tone on a Mhz 
band is a call for a new crystal in the second oscillator. Not something you 
have to do now, but it gives you a chance t get things on the shopping list.

OK so now you done all this and life is still not wonderful. You may need to 
pull the RF deck and do a band switch alignment.

More mail to follow on that subject.

Please let us know how these simple checks went.

Roger KC6TRU