[R-390] Nolan Lee's 1998 EAC overhaul narrative

[Don Reaves]

I asked if anyone had a copy of this, and Don Heywood responded.  Thanks, Don!

Here is Nolan's original post, only slightly modified for format by me
for a little better readability.  Text and typos unchanged.
For you newcomers to the list, Nolan has been absent from the list
several years due to health issues so we can only preserve his
amusing, yet informative stories and pass them along from time to
time.

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Nolan Lee's EAC R-390 Overhaul Description, 1998

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 amoung 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. he 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 groves seems pretty
consistent, but I was curious if the two groves were machined at
exactly 90 degree angles to each other. The groves 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 Drops
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 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 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 the six
variable IF slugs. They are different from 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

-----snip-----

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.
---

Don