[R-390] Ultimate heresy answered

Mon Jan 2 23:37:59 EST 2006

Notes on capacitor and resistor failures:
http://freespace.virgin.net/paul.zimmermann/Electronic/fault3.htm

http://www.aviationtoday.com/cgi/av/show_mag.cgi?pub=av&mon=1100&file=column2.htm

and from:  http://www.dilabs.com/about/faqs.aspx
"Why do some capacitors age?
Some of the higher dielectric ceramic formulations, ferroelectric ceramics, 
display a crystalline change that causes a decrease in capacitance with 
time.  This is a consequence of the basic chemical formulation, the 
microstructure of the ceramic, and the relaxation of the strain energy 
within the crystalline lattice.

The reference time, t = 0, for the aging phenomenon is the time which the 
ceramic was last exposed to the Curie temperature.  Curie temperatures vary 
with ceramic formulations and can range from room temperature to 150 oC. 
Thermal influences due to the external environment and manufacturing 
processes can reset the aging clock.

This variation in capacitance is predictable and repeatable.  It should be 
considered during the design phase to insure selected capacitance values 
will be adequate for the anticipated life of the application.  Operating 
temperatures should not exceed the maximum specified component 
temperatures."

And:

http://my.execpc.com/~endlr/aging.html

"Class 2 ceramic capacitors go through a logarithmic loss of capacitance 
(ageing) after manufacture because of the slow realignment of the crystals 
of barium titanate after baking.  In general, the higher the K, the faster 
the ageing.  Because of this, electrical measurements are typically taken no 
less than 24 hours later (some people recommend 1000 hours).  Baking the 
capacitors for several hours at 130-150C restores the capacitance to it´s 
original value (should you want to), and the ageing starts all over again. 
High voltage also tends to turn back the clock somewhat, and some test 
procedures take this into account."

It happens.

Jim M.

Jim M.
----- Original Message ----- 
From: "Cecil Acuff" <chacuff at cableone.net>
To: "Barry Hauser" <barry at hausernet.com>; "Perry Sandeen" 
<sandeenpa at yahoo.com>
Cc: <r-390 at mailman.qth.net>
Sent: Monday, January 02, 2006 11:18 PM
Subject: Re: [R-390] Ultimate heresy answered

> Hey folks
>
> Dallas' work, for those who are interested, is being posted on the 
> Kongsfjord DX site.  Seems he's been subjecting molded caps to extremes of 
> temperature to try and simulate the SJC environment to back his argument. 
> He doesn't have much nice to say about this list and it's membership. (no 
> surprise)
>
> His irrational behavior got him bounced from the list...nobody to blame 
> but himself.  Sorry to hear of his medical problems if in fact that is 
> what has happened. (same has been said of Nolan but I think there is more 
> to that story as well)
>
> Dallas contributed much in the past to the work on the R-390A but most of 
> the difficult work being done today on the R-390A is by those brave souls 
> that will take the time and make the effort to bring back to life the 
> abused of the series....those left out in the weather at SJC.  Dallas 
> admitted he had never seen one...nor would he ever own one...but spoke 
> with great authority about all the problems they have and why they were 
> not restorable. Not so....as can be attested to by many on this list. 
> More work...yes! More rewarding.....I think so!
>
> The days of the cherry surplus R-390A is near it's end.....just ask Mish 
> and Rippel.  A lot of the stuff they are seeing now days to restore are 
> for the most part a mess.
>
> Walter Wilson's web site has pictures of what can be done if one will take 
> the time and make the effort. www.r-390a.us
>
> It can be done!
>
> It has been done!
>
> Cecil.....
> ----- Original Message ----- 
> From: "Barry Hauser" <barry at hausernet.com>
> To: "Perry Sandeen" <sandeenpa at yahoo.com>; <aa9il at sbcglobal.net>
> Cc: <r-390 at mailman.qth.net>
> Sent: Monday, January 02, 2006 9:19 PM
> Subject: Re: [R-390] Ultimate heresy answered
>
>
>> Perry wrote:
>>> Unfortunately, these vocal few have driven off the list Dr. Jerry and 
>>> Dallas Langford who
>>> have contributed to vast improvements for the R390 and R390A in 
>>> particular and other BA equipment
>>> in general.  Between them, they may have forgotten more about BA's than 
>>> most of us now
>>
>> Yup -- unfortunate all right, but that's not the reason Dr. Jerry left --  
>> I was in touch with him afterwards.  Didn't care for the foolishness that 
>> sometimes erupted on the list and some other disagreeables, but wasn't 
>> necessarily about solid state mods or the like.
>>
>> You're about 180 degrees out of phase on Dallas (Lankford with a "k" that 
>> is).  The last time he stormed off it was due to conflict over recapping. 
>> He asserted that he never found a bad molded cap (i.e. black or brown 
>> beauty) and went as far as to assert that those who claimed finding leaky 
>> ones were  (paraphrasing, but not by much) misinformed, delusional or 
>> outright liars.  Some list members even posted links to photos of 
>> physically split caps.  I attempted to smooth ruffled feathers privately, 
>> pointing out that many of the list members' experience reflected St. 
>> Julien's Creek Massacre victims -- blue and yellow stripers -- that had 
>> been outside for over a year.  (Of course, those caps can fail on the 
>> shelf or in a radio cozy on the shelf --  I was just trying to be 
>> diplomatic.)  No good.  He accused me of being "an apologist for the 
>> recappers."  Your post would have been enough to make him go ballistic 
>> all by itself.
>>
>> As I learned later on from another list member, Dallas had suffered a 
>> stroke sometime before, and that probably has more to do with it all than 
>> anything. Dr. Jerry is active on the Collins reflector.  I imagine there 
>> are plenty of Collins collectors on that list who are traditionalists who 
>> would rather keep the gear as original as possible and true to its design 
>> of the times, and probably more so than on this reflector.  He seems to 
>> be getting along there just fine, though he is missed here.
>>
>> Barry
>>
>>
>>
>>
>> _____________________________________________________________
>> R-390 mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>> Help: http://mailman.qth.net/faq.htm
>> Post: mailto:R-390 at mailman.qth.net
>> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
>>
>
>
> _____________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/faq.htm
> Post: mailto:R-390 at mailman.qth.net
> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
> 