[R-390] Fwd: 2 questions from a new user

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One of my favorites from Nolan:

> From: Nolan Lee <nlee at gs.verio.net>
> Date: June 6, 2000 at 11:47:06 PM EDT
> To: r-390 at qth.net
> Subject: RE: [R-390] 2 questions from a new user
> Reply-To: Nolan Lee <nlee at gs.verio.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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