[R-390] no vendor tag: any way to ID vendor?

[Roger Ruszkowski]

Kevin,

A not engraved front panel is a clue you may have an early 
production model.

Not necessarily a Collins build.

On the IF deck does it have trimmer caps on the
mechanical filters?

Is there four holes in the left side that let
you adjust the trimmer caps on the
under side of the mechanical filters
with out the need to remove the IF deck
to adjust the bottom caps.

First was no trimmers.
Then was trimmers and no adjustment holes
Then was the adjustment holes.

All the decks should have manufacture names stenciled on them.

But decks got swapped all over the place and are not a real clue.
You can have a IF deck with trimmers in a frame with no holes

Or no trimmers in a frame with holes.

But the decks could be a clue.

All the manufactures did a good job building the receivers
and any one from any run has an equal chance of being a
great receiver.

Love and cleanliness can bring any gear train into excellent 
easy operation.

More love and adjustment  will bring any receiver into good
operation.

Changing some caps
A leaky black things.
B some just need better values.
will bring the receiver past good to improved.

Then you start selecting and swapping tubes doing more alignment
and any receiver can be brought into excellent operation.

Its not who built the receiver its who is maintaining the receiver today.

There is a group of audio people who rant about tubes and what they hear.

Do not let that fringe group overly color your knowledge.

Picking and choosing tubes in the receiver can and will change the
signal to noise ratio in ways that can be measured with meters.

Changing some caps in the audio path will open up the frequency 
response. One side is more noise but better voice audio.

The other side is narrow reception better signal to noise and 
hearing weaker CW signals. (also TTY and today's other narrow band digital).

Changing some caps in the IF deck will take the noise down.
within limits of logic but a couple DB here and couple DB there
and soon you have 27:1 rather than 10:1.

As long as you have to move those big black plastic slug
out of the IF and RF deck, you mite as well up the value
by 10 on the bypass caps. Just getting good caps back in the
signal path will do for those caps. Changing their value need
care. A blanket statement does not cover the subject.

There is only 6K plus pages in the pearls of wisdom 
PDF so far. If you can not memorize it all, at least
look through it once and read a few topics of interest.

It is also available on line in small subject files.

Do not let that scare you.

Down load the Y2K manual

Down load a copy of TM 11-5820-358-35   R390/A

Down load a copy of TM 11-5820-357-35   R390

There are thing in the R390 manual that did not make the R390/A manual 
like how to adjust the very first cap in the antenna trim section.

Roger AI4NI