[R-390] Nolan Lee Repost

[Walter Wilson]

This is one of my favorites from Nolan

---------- Forwarded message ----------
From: Nolan Lee <nlee at gs.verio.net>
Date: Tue, Jun 6, 2000 at 11:47 PM
Subject: RE: [R-390] 2 questions from a new user
To: r-390 at qth.net


At 07:21 PM 6/6/00 -0400, you wrote:

 I thought the metal-cased Vitamin-Q caps were the ones to get rid of, and
> that the yellow-waxy ones held up better.  Now, I hear the opposite.
>

Change ALL of the paper caps, period. It's cheap insurance. Undoubtedly
someone will tell you otherwise. I've listened to people bitch and
moan about the amount of effort it takes sine I first brought up the
idea back in late 1998 but it's well worth doing.

"Ooh, it's too hard and I might burn my little fingers or break a nail."
"I'll miss Star Trek tonight..."
"Whine whine, I've got a hot date with a pair of Swedish nympho twins".
"My dog chewed the cord off of the soldering iron."
"The voices in my head said not to."
"Those caps have worked fine for the last 45 years, why?"
"If it ain't broke, don't mess with it."

Yeah, right. Who needs Gatling guns, we can travel faster without
them....

I've listened to dozens of reasons why there is no need to change
them and it's a wasted effort, etc. I still think that for the person
that actually uses their radio and doesn't have it as a trophy sitting
on a table somewhere where they stare at it while they drink some
sissy drink like lite beer or some twisted version of coffee that
doesn't even contain chickory, and intend to keep the radios for
the duration, should put forth the effort and change the caps.

Yep, it's takes time, and the IF deck is a pain in the ass. I'd
guess that doing nothing but changing the paper caps themselves
in the radio will easily eat up 15 or 20 hours if you take your time
and are very careful and cautious. You end up spending more time
than that because while you have the beast apart, you'll want to
check the value of all of the carbon composition resistors and
replace the ones that are out of spec. Cut up a beer can with a pair
of scissors and make yourself some assorted sized of soldering shields
to protect the wiring harness, etc while you're soldering. Pick up
three of four hemostats for heat sinks, to clamp to the leads of
any carbon composition resistors that happen to share a common solder
connection with some of the caps you'll change. This decreases the
change of changing their values up out of spec.

It takes effort, but that's nothing compared to spending days or
weeks tracking down little quirky AGC problem and a host of other
problems that over time, I can almost guarantee you 100% that you
will have with those 35 to 45 year old paper caps.

 Are the yellow waxy caps really that bad?  If so, I have a lot of soldering
> ahead of me...
>

They aren't anywhere near as bad as the old brown tubular caps, but
we're still talking about 30+ year old paper capacitors.  ;-(

Do one module at a time. Pull the RF deck for a good cleaning, and
mechanical alignment. While it's out, change the three axial leaded
paper caps and test the hell out of the stud mounted one next to
the 6DC6. If it's less than perfect, change it. It's seldom
that if fails but test it while you have easy access to it. As a
rule the oil filled paper caps are probably the most reliable paper
caps made. I've got some here that are pre WWII and they are
perfect.

The next time you fell energetic, pull the AF deck and replace the
caps under it, they're a snap. Also replace the axial leaded tantalum
while you're in there.

Save the pain in the ass IF deck for last. You can knock it out
in a couple of two or three evenings of "casual" work. Remove the
BFO osc can and the long shaft for the bandwidth switch and it
makes the job much easier. Be very careful with the insulated posts
that some of the caps attach to. Too much heat for two long of a
period of time and they break very easily.

Replace the caps in a logical order and try to duplicate their
positions and routing of the leads as closely as possible.

I've owned and played with R390A's since the mid 1970's. This
last one that I did, I replaced all of the paper caps in and took
a lot of steps to make sure that it would be reliable as possible
when I was done. As of today, it's been running twenty four hours
a day and seven days a week since the overhaul which I finished
back on the 13th of October of 1998. A little quick math shows
this to be in excess of 14,000 hours. That's 14,000 hours in a
an uninsulated masonry building with temperature extremes of below
freezing in the Winter and well over 115 degrees during the Summer.
Let's not forget the humidity down here in South Louisiana either.

It's sitting here running on a variac at 114 or 115 volts as I type
this. The electrical and physical alignments are still solid, the
sensitivity is still wonderful, and other than changing out a few
tubes a while back, nothing has been done to it in this time period.

I have never had an R390A give this level of reliability even back
in the 1970's when the radios were twenty five years newer than
they are today. That's not saying that it won't try to burn the shop
down tonight while I'm sleeping or try to electrocute me the next
time I go to adjust the volume or something, but I kind of doubt it.

thanks,
nolan


"if you see us running, catch up"
bomb squad motto

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