[R-390] Cleaning Chassis and rebuliding -Long

[Barry Hauser]

Hi Pete & gang:

>This has become even longer.

Today I did some more work on the current BLUE STREAK project here. (Not the
1960s Missile Project but the St Juliens renovation!)

>A blue striper from one of the usual sources?

<snipped>

I have the rebuilt St Juliens receiver working very well, astonishingly so
in
fact. Especially as it was a pretty badly corroded and sand laden example
from the massacre. I have been working on it on and off for about four
months
now.

> Ah, yes, the massacre, not a pretty sight.

I washed the IF, PSU and audio decks in hand washing soap and warm water,
with plenty of pure tap water wash off, then dried them in the clothes
airing
cupboard for about two weeks.

>Dave Medley goes as far as to do the final rinse (before sun baking) with
distilled water.

 I took great care not to get the IF transformers wet, but other than that
the chassis and components were all cleaned and came up beautifully. I was
amazed by the amount of dirt and grit washed off into the bowl after the
initial cleaning.

>Imagine if the rig was cleaned before it was shipped.  You could have saved
on shipping. heh heh

Last weekend I stripped the RF deck of its transformers and painstakingly
dismantled and cleaned every face of every paxolin cheek in each
transformer.
 I remember Nolan saying that he found the deposit on these surfaces to be
conductive, so I didnt want to take any chances here!.

>I remember Nolan, but not that.  Can anyone add to this -- is there a
special coating?  (BTW, anybody hear from Nolan lately?)

I used a QTIP (Cotton bud, here in UK) to clean inside each coil former and
around the ceramic caps. I used methylated spirit for this work, taking care
not to get too much on the coils themselves. I used a fresh cotton head for
each face so as not to cross contaminate from one piece to another.

>What's another name for "menthylated spirit", or a US translation?

During the RF deck cleaning I found the wrecked 2-4MC antenna transformer.
It
had me foxed as I could not get at the fixing screw on that particular unit.
It was obscured by debris inside the can. When I finally got the transformer
off the chassis I found the remains of three slugs and the broken former
lurking inside. Totally useless!

>Did you order a replacement?

The RF deck was washed with kerosene, and thoroughly cleaned. The metal was
perfect under all the dirt that had built up on it. The deck is a Collins,
as
are most of the transformers. I re lubed the moving parts and used Molyslip,
applied with a Qtip on the sliding faces and bearing surfaces of the slug
racks.

>"Molyslip" sounds like the Dow Metal Assembly Paste I use.  This stuff is a
jelly-like charcoal gray stuff in a tube.  I found that it's best applied
like a polish -- rubbing in and buffing out or burnishing.  The molybdenum
works its way into the microscopic pits in the surface of the metal, making
it more slick.  I then use a very small amount of synthetic lube, like Mobil
One.  The combination is particularly effective, however the moly paste
itself is not much of a lube just painted on.  Moly treatment (burnished in)
is particularly good on the cam follower slots and the cams themselves --
they're stamped and have fairly unfinished edges.

On re assenbly I straightened all the slug springs . I didnt have any talcum
powder to hand at the time so I have left applying talc until later, if at
all.

>There's a difference of opinion on whether talc is worth it or not.  Did
you tweak up the adjusters on the slugracks to re-align the slugs?

A major worry was the coax relay. It was very badly tarnished and showing
powdery corrosion in places. I guess that my radio had its back to the sea
at
St Juliens, as the rear of the set has taken the brunt of the corrosion and
dust ingress.

One of the coax relay coils was open, so I decided to strip the relay, clean
and rebuild, which I did today.

>Tell us how you went about that -- wire used, turns, etc.

I used Goddards Silverdip, which is a silver jewellry cleaner available from
supermarkets here in UK and possibly internationally.

>I don't know if that was such a good idea, from prior threads.  Sounds like
the same clear liquid like Tarn-X sold here, and maybe internationally (used
to be an infomercial product).  Foul smelling when in use.  Word was that
it's too aggressive and that anything cleaned with it tends to oxidize more
rapidly.

I dumped the silver parts into the liquid and scrubbed them with a
toothbrush.... the Silverdip has magic properties and restores a clean
silver
finish to most parts after about five minutes immersion. (BTW it is only
about �2 a bottle, enough for about 4 R390s). So having rewound the magnet
for the whip antenna channel and re assenbled the relay parts, I now have a
pretty good looking coax relay at the back of my set.

>It restores that shine by taking off the oxides, and again, word was some
of the un-oxidized metal as well.  That's a problem with plating.  Better to
use something like DeOxit.  Even though it doesn't magically shine that
well, if you just burnish the mating surfaces and apply some DeOxit, that
generally does the trick without risking what's left of the plating.

I also changed the selenium (?) rectifier for the relay supply, as I found
it
had one poor leg.

>Poor thing -- I think protocol is to shoot them. ;-)  Yup, they are
selenium.  Don't throw it down the well, though some vitamin/mineral
supplements contain selenium, so I don't know...

 I guess this might be why one of the relay coils has gone
open in the first place. I replaced it with a silicon equivalent, using the
old rectifier mounting bracket for the new one. I added a 100volt 100uF
electrolytic across the dc side of the relay rectifier. I found that this
reduced the hum from the relays when they are energised. A tip worth noting!

>Interested in other opinions on this -- -should this be a standard "mod".

I recapped the audio deck and added 47uF 400 electrolytics beneath the
chassis to the audio decoupling components. What an incredible uplift in
audio output and quality.....Definitly worth doing that on any set with
30year plus elecs in it.

>Tell us more about this.  How many and where exactly?  Did you
reform/replace/bypass the plugins?

The EAC IF deck seems ok, so no recapping there yet except for trhe dc
blocker berfore the Mechanical filters...just a precaution! I used 0.01 2kV
disc ceramic as it was to hand and fitted in easily.

>Does it matter what type -- I generally use an orange drop or yellow poly
tubular.

I was hoping to report the repair of the 200kc Calibrator crystal, but alas
that was not to be..... The crystal was loose inside the HC6/U can, and
therefore the calibrator would not lock. I opened the crystal and attempted
to resolder it to its mounting posts. I used a heat gun and LMP solder  Any
way, my attempt failed as the crystal now oscillates at 275kc. I guess it
has
cracked under the heat. I thought it was a long shot any way!

>Did you heat sink the xtal -- or is that even possible?  Suggest you put
the modifed xtal up for auction under "@RARE@ 275 KC Calibrator Crystal".
Who knows, maybe someone out there is looking for a bleep every 275?

So, in finishing the receiver is working well on all excepy the 2to4 MC
banbs, but without a calibrator. The PTO needs stretching, but I will tackle
that next week. In the mean time the rig is back in my shack and I am
listening to it for a while!

>Whew, I think you've done quite well.  Listening?  Oh, right, I almost
forgot. ;-)

More updates later.

>Good -- and thanks for the blow-by-blow.

Barry