[R-390] Call For Information

[Randy and Sherry Guttery]

On 3/7/2011 4:33 PM, Perry Sandeen wrote:

 > Its premier performance is obtained at the cost of 
complexity. Attempting to
 > maintain or repair it without a good fundamental 
background is a recipe for disaster.

Initial thoughts:

There is only one really *absolute* (use it) / *no excuses* 
(find one) / *don't do it* (try working on the gear train 
without it) item with the 390/1 that is completely unheard 
of with the 390A: and that's the "Green Gear". Since there 
is no counterpart on the "A"s - if it's missing from a 0/1 - 
many people don't have a clue. In fact I've had to help put 
a 390 back together that had a green gear (still in it's 
storage spot) - as the owner didn't have a clue what it was. 
OK - yes - it's not that hard to re-sync a geartrain... but 
it's a heck of a lot easier to not have to. So it's one item 
that needs the "hey newbie - it's there (or supposed to be 
there) for a reason!" treatment.

The only other thing that is totally different is the 
alignment of the IF - since it is both variable band width 
and all LC (vs mechanical filters). (OK I'm glossing over 
the power supply - but really - if someone can handle 
double/triple hetrodyne - a series pass regulator - even 
with quad plates - shouldn't be much of a challenge).

Regarding manuals - I've never seen an "official" R-390 
manual - not that I recall. Sherry managed to snag an 
original Collins R-391/URR instruction book stamped 
"NAVSHIPS 93766" with a rubber stamp. I had "assumed" 
(there's that dangerous word!) that it was basically the 
same as the R-390/URR manuals - just with the addition of 
the auto-tune "stuff" - particularly since many of the 
diagrams are marked TM 856-xx except for the autotune 
related illustrations - which bear TM 863-xx (which is the 
primary reason behind my "assumption" that the TM 856 was 
for the R-390/URR and TM 863 being an "ammended" version of 
same for the R-391/URR). I've always thought the 856 / 863 
better than the original TM 856A for the R-390A/URR - as it 
seemed to go to great lengths to explain many things. It 
seemed that the 390A was the "new improved economy version" 
of the 390 - and it's manual was equally an "economy 
version". For instance - the function switch in the R390/1 
S107. There is a page where each of it's four poles are 
shown through all six positions(TM 856-96)... I'm not aware 
of that for the 390A. The 856 also spends a good deal of 
time describing the IF... and how each stage works in the 
"grand scheme" of things... While the 390A manual is heavy 
on the mechanical filters... not on "each stage"... Yes, I'm 
being picky here - but my point is - I think the original 
856 was pretty good - judging by the (apparently 
preliminary) 863 I have. Sure - there are some "nice to 
know" things about the 390/1 that would benefit from similar 
thorough treatment as the 390A Y2K(R3) manual - but 
considering the much less "economical" design of the 390/1 - 
most of the work needed in restoring one is pretty "straight 
forward".


One issue with the 863 version (and likely the 856) - who 
has a printer large enough to print that large master 
schematic / wiring digram (Figure 116 TM 863-106(1) and TM 
863-106(2) ). I don't recall exactly - but they are 
something like 21 X 36 inches each ??? Wonderful for working 
on the radios - everything "at hand" in one place (they fold 
out opposite each other to take up a table top or such - but 
as noted - everything in one "view"...

So Perry - I think it's good that you've called for "input" 
- I'd assumed the 863 was pretty much "it" for the 391 (and 
by default it's older sibling) - but there may well be some 
"gems" that would be interesting.


best regards...

-- 
randy guttery

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