[R-390] Re: Thinking of Nolan Lee

[Daren Q]

I'm one of the many lurkers on the list and to be frank I remain
that way because I have nothing to contribute. None the less,
like the rest here I am fascinated by the R-390a, and look
forward to having mine back in the near future. I too genuinely
miss the input of the list's resident philosopher Nolan Lee, and
was pleased to see some of the reposts that have surfaced
recently. As for his detailed description of his EAC rebuild, it
came through on my end somewhat chopped-up as in a forwarded
mail. Due to the fact that it contains much of Nolans inimitable
insight, I stripped and cleaned it, and did my best to
reorganize it and make for an easier read. I figured that others
on the list might possibly appreciate the effort and want to
save the post, so here it is ..... DQ
       -------------------------------------------------
 
Below is one of the typical posts from my friend Nolan. I think
we all enjoyed his posts and writing ability. 
73,   Don WC4G
       -------------------------------------------------

(May 1999) I've had a couple of requests for the list of items I
did when I went thru my EAC last year so I'm reposting my
original message on it to the list. The EAC has been running
24/7 since October of last year and I have no complaints. I've
been wanting to pull it out of the rack and do a "visual" of it
and check the tubes and the alignment but haven't had the time.
Maybe this Fall. Your mileage may vary ......... Nolan
 
               -----snip from Oct 1998----- 
Well, after spending months slowly going thru my two R390A's,
one is finished. Below is an outline of the steps that I took
during my overhaul. This was probably one of the more evolved
R390A "overhauls" done in the South. The other, will take
longer, I'm probably going to replace all of the bushings in the
RF deck among other things that I didn't do with this one. The
victim: I started with a cherry 1967 EAC contract model that was
the "lowest mileage" R390A I've ever seen. All of the original
modules, meters, covers, etc. were still on it. In addition, all
of the tubes in it had date codes within a two or three month
period of each other in 1968. Even with clean gears, there
wasn't even a hint of a wear pattern in any of the gears and all
of the aluminum finish in the tracks on the RF deck was still
intact. The green paint on all of the module hold down screws
was even 100%. I'd be surprised if this thing saw more than a
few hours operation after the burn in period. There's no diode
load hole in the front panel or adjustment hole in the top dust
cover for the meter adjustment. :-)
 
Jerk all of the modules out of it and rip it's gizzard out and
scatter and toss the parts around! I tried, but I managed to not
loose any of the parts and didn't even have any extra ones left
over. Chassis: Tested the dial lamps, checked the value of all
of the resistors, the diode, the 2 capacitors, the meters,
tested the selenium rectifier, and the antenna relay and
inspected the contacts in the relay. Verified function of the
main power micro switch, it's placement, and measured the
resistance of it. Measured the resistance of all of the front
panel switches and potentiometers, and very lightly lubed the
shafts of each, checked the ovens switch, verified the values of
the fuses, checked their resistance, replaced one of the fuse
holders that I didn't like the look of with a NOS one, and
replaced the rear panel IF connector, the center terminal was
missing. Checked the line filter, and checked the tightness on
all of the screws holding the whole damn mess together. :-)
 
I removed all of the knobs and inspected and lightly lubed the
set screws. Also verified that the index washers were installed
in the two big knobs that prevent the clamps from turning. The
next step ate up a lot of time. I removed all of the hoods of
the chassis connectors to inspect and then measured the
resistance of EVERY damn wire in the chassis. Then I installed a
NOS military 3 wire 8 foot rubber 16 gauge power cord with a
molded plug. Nice and flexible SJ. The original strain clamp for
the cord was still there. First one I've ever seen. :-)
 
Power supply module: visual inspection, resistance readings of
the transformer windings, and wiring, inspected the solder
connections, verified 115 volt setting, stuffed two new 26Z5W's
in it. Checked all of the screws and nuts for tightness. :-)
 
PTO: Why bother? Chunked it in the R390A parts pile and
installed an Army rebuilt Cosmos that I've been sitting on for
about ten years, sealed in the box, to replace the Cosmos that
was in there. It turned out that the endpoint was out a little
less than 2 KHz, and linear within a little less than 200 Hz
across the spectrum. I don't know what the specs on it where
when it left their hands in Feb. of 1984 but it sure aged well.
:-)
 
I guess that I'll let it run a few weeks and then adjust the
endpoint. I did power up the oven and verified that the
thermostat worked, measured the resistance of the transformer,
and tested the tube. I like the Cosmos PTO's. That blue label
sure is pretty, bubba! On a side note, I probably use a bit more
complicated method than most people do when fitting a PTO to a
receiver. If you're going to do it right, it might as well be
done right the first time. Both halves of the oldham coupler
should be perfectly parallel to each other and the centerline of
both shafts should be perfectly in line with each other on both
planes. I only spent about an hour adjusting the position and
height of the PTO in the chassis, but spent several hours
measuring the components and setting up the fixtures to measure
other aspects of the components. I first measured the run out of
each half of the couplings while installed on their shafts. The
one on the PTO was true within .001. The one on the KHz shaft of
the RF deck was machined improperly. The rib was .003 off to one
side and wasn't square with the bore either. I tossed it and
pulled a few others out of spares. It took several before I
found one that was square with the bore and only had a little
more than 0.001 run out. The next step was to check the center
section. The width of the two grooves seems pretty consistent,
but I was curious if the two grooves were machined at exactly 90
degree angles to each other. The grooves were of a dimension
that I didn't have any key stock for so I used two 12" long
pieces of 1/4" ground steel rod. I centered the two pieces of
rod, lengthwise, one in each of the two grooves, clamped the
three pieces together. Then by measuring and comparing the
distances between the four rod ends, I could determine the exact
angle that the grooves were from each other. This part of the
process was a wasted effort, the coupling center piece from the
EAC was 90 degrees like it should be and so where the ones in
spares that I checked. :-)
 
When I finally assembled the receiver and physically aligned the
PTO to the chassis, mechanically and electrically, the dial
indicator measured a total movement in the center section of the
oldham coupling of .003 when the KHz knob is turned. Close
enough! Put that spring on! Oh, I used a little dab of Penzoil
wheel bearing grease to lube the coupling. It's red and
contrasts, in a pleasing fashion, the blue label of the Cosmos
PTO. :-)
 
Crystal Oscillator Module: Tested the tube, and tightened the
screws holding the tube socket to the chassis, they were loose.
Checked resistor values, transformer windings and crystals. Bad
10 MHz crystal, throw one in it from spares. Most are still on
the money, the few that are "off" are well within 1 KHz or maybe
a shade more. I decided against spending ~250 dollars on new
ones. Measured the resistance of all of the wiring and switch
contacts and tested all of the fixed capacitors and spun all of
the trimmers a couple of turns. Powered up the oven and verified
function of the thermostat. Also, "timed" the two switch bodies.
They were "off" a bit. Then when thru and re tested everything
on it's underside just to make sure. I figured that anything
that was a pain to remove, I double check everything. :-)
 
Audio module: One of the original plug in electrolytic caps
showed signs of leaking, tossed it in the trash, installed
another one from spares. Reformed both, leakage at 50 volts over
the rated voltage was less than 1 ma. per section after
reforming. I fused them and ran them for a couple of weeks at
full rated voltage on one of the HV supplies, they didn't
explode and leakage declined even further. Good enough, bubba!
(yeah, I know, Doc, but the power factors were good, I even
checked that. :-) Ripped all of the paper capacitors out of the
module, and tossed them in the trash. Installed two new .022
400V orange drops in the location that Chuck likes, and NOS
Vitamin Q's in the other locations. I have the orange drops on
hand and could have used them thru out but didn't like the way
they sit on the circuit board. I did use an Orange Drop to
replace the one on the chassis under the circuit board. All of
the new caps were tested for leakage at their rated voltage and
tested to verify their value before installing. Checked all of
the resistors for value, replaced a couple. Tested the mica cap,
no problem there. Tested all of the tubes, they all passed but
tossed the 0A2 and stuffed a new 6626 in it's place. I don't
trust used 0A2's, had some weird problems with them. Tested the
relay and measured the resistance of the wiring, the chokes, and
the transformers. I left the 800 cps filter alone. Probably not
a whole hell of a lot of R390A's out there that still have their
original 6AK6's. All of the tubes are original except the
rectifiers and the regulator. :-)
 
IF Module: Tested the tubes and the 3TF7. Measured the
resistance of the wiring, the transformers, the switch contacts,
and the resistors. I replaced more than a half a dozen resistors
that were out of spec. Checked the capacitors and resistors
inside the IF transformer cans, that could be tested. Some could
not be tested in circuit. I tested the big above chassis oil
filled capacitor for leakage and value. Tested all of the mica
capacitors for leakage and value and then ripped all 18 or so of
the axial lead paper capacitors out of the module and tested
them just for kicks. EVERY "brown beauty of death" tubular
capacitor that was in it leaked like hell and a good percentage
had microscopic cracks in the bodies within maybe .020 of the
seams and paralleling them. Most of these caps leaked at
voltages below 50 volts when tested. Only one of the metal can
axial capacitors leaked when tested. I replaced all 18 of the
capacitors with Orange Drops. For the .1 and the .033 values I
used 400VDC rated ones and for the .01 values, I used 600VDC
rated ones. The reason that I didn't use 600V rated ones thru
out was their size. It was a pain in the ass to the fit the ones
that I used in there properly. If I'd have used the 600V ones
everywhere, I'd have had to move the locations of some of the
capacitors and a bunch of them would have had excessively long
leads. I didn't think that this was such a hot idea in the IF
section and figured that the best placement of the parts was in
the original locations. ;-) 
 
Let's see, other than checking all of the screws and nuts, I
think that was it for the IF deck other than lightly lubricating
the shaft extensions where they passed thru the front of the IF
module chassis. I didn't test the mechanical filters. I tested
the blocking cap before I tossed it and it had tested good even
at 100 volts over it's 300V rating. Whew! The last one, the RF
deck: After removing it, the first step was to take it apart. I
removed all of the tubes and tested them, the crystal oven and
tested it, all of slug racks and springs, four of which (for the
variable IF slug racks) were really weak, so I installed NOS
ones in that location when I put everything back together.
 
The geometry for those 4 springs suck, they're stretched a lot
more than any other location. I removed all of the RF coil
assemblies and measured the resistance of all of the windings
and checked what capacitors I could. The bridge wouldn't work on
some, so I kept track of those in case I had some weird assed
problem when I tried to align it later. I disassembled the gear
train and tossed all of the parts, except for the counter, in a
coffee can and sprayed a mess of gunk in there and let them
brew. They weren't really dirty, but the original lube had
mostly evaporated and what was left was stiff as hell and I
don't really find the gear train much of a mechanical challenge
so I ripped it apart. About the only thing I didn't take apart
was the 6 camshafts and the antenna trimmer can. I worked a few
drops of penetrant into the bearings of the cam shafts and kept
lubing and wiping them until only clean oil would come out. Oh,
I used 10w30 Mobil 1 synthetic oil for the RF deck except for
the detent where I used Penzoil wheel bearing grease. Two of the
cams appear to have been stamped, I guess, with cracked dies,
leaving a couple of sharp burrs on the surface that the rollers
ride on. I stoned these down while maintaining the original cam
profile. :-) 
 
When you take the split gears apart, tie them together, with a
bit of soft wire in the orientation that they were originally
assembled with. I suspect that the halves were matched. While
all of the stuff soaked, I replace the three paper capacitors,
with Orange Drops, and replaced close to ten resistors that were
out of spec, checked all of the other capacitors and found a
cracked 005 1KV ceramic disc. And yes, I measured the resistance
of all of the wiring and of the band switch. ;-)
 
I found an odd thing. One of the tube sockets only had one screw
holding it to the chassis. When I attempted to install a screw
there, it turned out that the little "C" shaped piece of metal
that curves all of the way around one side of the socket had an
unthreaded hole in it for the screw. I'm surprised that an
inspector didn't catch this at the factory. I tapped the hole
and moved on. Most of the gear clamps were either viably cracked
or showed cracks when dye checked. I guess that they must have
been over tightened when it was built. I replaced all of them
with NOS clamps to be safe. I found that several of the roller
retainers had been over staked on a couple of the slug racks.
This prevented the rollers from turning. In addition, a few of
then ends were not square and had to be straightened. Burrs and
gouges on the end surfaces had to be stoned down and polished.
The fit and finish of mechanical portion of this EAC RF deck
didn't impress me at all. The old Collins decks were much more
finely finished mechanically. I wiped each of the RF cores out
with a pair of damp Q-tips, wiped the slugs off, and eye balled
them. The Collins part numbers on all of the RF slugs are all
the same EXCEPT for the six variable IF slugs. They are
different from the rest of the RF slugs, so they aren't
interchangeable. ;-)
 
I assembled the RF deck and mechanically aligned it and put the
receiver back together. For what it's worth, the repeatability
of the RF slug racks averages about .001, the repeatability of
the variable IF slug racks averages .004 on one and .005 on the
other. I suspect that this could be improved upon by relocating
the location of the attachment point on the chassis of those
four springs. This would require either shorter springs or
possible just creating spring "wells" that extent slightly below
the chassis so that standard RF deck rack springs could be used.
I fired it up and let it cook a while in Standby mode, at 7+000.
None of the magic smoke escaped so I switched over and set the
PTO to 2455 KHz and tightened the clamp. I stuck a VTVM lead
into the unbalanced antenna connector and cranked it down to WWL
on 870 and let it run more than a day before I did the first
alignment. I always like to align a receiver twice. I go thru
it, and then when I'm finished I start all over again. I've been
playing with it for about a day and a half since the alignment.
This is the most sensitive receiver I've ever owned. It kicks
ass.
 
I did a few sensitivity tests using my URM-25F. I questioned the
results so I dug out the URM-25D and tried them again. REAL
close. I started with a receiver that hadn't been abused and
tried to do the best job that I could going thru it. I wanted
something that I didn't have to screw around with every few
weeks. Something that wouldn't wake me up at night with a burst
of light like a Romulan disrupter (I've had R390A's do that
before). Something that would sit there and run for month after
month and need nothing but tube and dial lamps like my
R-1051B's. Hopefully, this will do that. Many of the of the
steps that I took, were "over kill", but I had fun doing it and
learned a few more things. The numbers you ask? Lets just say
that they're as good as the best sensitivity levels that I've
ever seen posted or in print on the R390A. Numbers, that up
until now, I always had my doubts about. Guess I better feed the
critters and make me a mess of grits for breakfast..
 
Nolan 
        
 ---   If an infinite number of rednecks, riding in an infinite
number of pickup trucks, fire an infinite number of shotgun
rounds, at an infinite number of highway signs, eventually they
will produce all of the world's great literary works in Braille.
 ---
 


                ..\!|!/..   
           .. ( @ @ ) ..
          ooO--(_)--Ooo
Greybeard 5150  aka: DQ
....
LOUD Pipes & Stars 'n Stripes . . . La Vida Bueno!
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