[R-390] RF Alignment Questions

[Barry]

> Some random thoughts on why the 2-4 Mhz band might be weak:
>
> Coils/trimmers badly misaligned.
> Slug rack is sticking for the 2-4 Mhz RF coils.
> One of the three RF cans for the 2-4 band may have an internal failure -
> they are made to be unplugged and replaced easily - the screw holding them
> to the chassis is accessed through the coil slug - with a small phillips
> head - after removing the slug rack).  Fair radio may have replacement
cans.
> I have opened cans and replaced caps that were bad.  I have also seen
coils
> that were fried either due to a lightening hit or a powerful nearby
> transmitter wherever the radio was used last.
> Possible bad trimmer cap inside one of the RF cans for that band - give
them
> a spin to loosen up any corrosion - if you cant get a double peak, then
> something is wrong in the can, either the trimmer itself or one of the
fixed
> caps inside the can.
> Another possibility is poor contact or corrosion on one of the switch
wafers
> under the RF deck on a contact associated with that band.
> If it is weak in just one segment of the band, then it may be a bad
crystal
> for just that segment, such as 2 Mhz, 3 Mhz etc., or the crystal needs to
be
> peaked using the associated trimmer on top of the oscillator subchassis.
If
> its the whole 2-4 band thats equally weak, its probably an RF coil.
> Alternately, if its just one segment of 2-4, the trimmer cap for the
> associated crystal could have gone bad - yes I have had to open xtal
> oscillator boxes and remove and replace individual trimmers - very time
> consuming but they do go bad.
> These are just a few random ideas - good luck.
> Jim N4BE

Unplug the can, DeOxit the pins, and re-insert it.  Just another random
thought.

Barry - N4BUQ