Returning to valve equipment for greater reliability?

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A correspondent in NSW, Australia says
"we live in a damp climate & solid state devices die prematurely"
tired of dying and burning-up modern kit like oscillioscopes with no
schematics or parts or knowledge to keep repairing them , they are making an
active change to resucitating and maintaining valve equipment.
So what is going on in the likes of NSW, I would have though dampness and
the high voltage of  valve kit would be more likely to failure. Or is it
just that the information and parts is out there for such repair .
Or is another route the construction of a sealed cabin with air supply
passed through a dehumidifier, a more sensible way of dealing with the
problem and retaining modern kit.



Re: Returning to valve equipment for greater reliability?

N_Cook wrote:
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   Where can I find a tube based four channel, 400 MHz Scope with
IEEE_488 interface, that is calibrated via software? One that I can save
the image, and print it out or save for future reference?  How many tons
of air conditioning will it need to keep from burning a hole through my
floor?

Re: Returning to valve equipment for greater reliability?
wrote:
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The OP story doesn't make much sense, unless he/she buys orphan
equipment that is very vulnerable.  I have used Tektronix and HP/
Agilent oscilloscopes and spectrum analyzers and other electronic
equipment since the late 1950's in all sorts of climates and never had
problems like the OP quoted.

Re: Returning to valve equipment for greater reliability?

"hrhofann@sbcglobal.net" wrote:
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  I have a Tektronix 324 scope that I pried out of mud, after a
bulldozer ran over it.  I gave the owner of the scrap yard $20 for it,
and hosed off the mud.  I loose Berg terminal was repaired, and I made a
power cord for it. That was about 25 years ago, and it still works. An
old Tek scope like the 535 will need new caps, and calibrated no matter
what the tube crowd thinks.


   Maybe the scopes in that story were near the sea and were eat up with
salt.  I saw a pile of old HP 5245l Frequency counters stored in an non
air conditioned building near Melbourne Florida. Just touching any of
the transistors was enough to make the leads break off.

Re: Returning to valve equipment for greater reliability?
on 1/06/2013, Michael A. Terrell supposed :
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There are many more damp climates than NSW Aus. Florida is likely one  
of them. l-)

--  
John G



Re: Returning to valve equipment for greater reliability?

John G wrote:
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   Damp?  You can grab a handful of Central Florida air, and squeeze a
glass of water out of it!  I've had it take all day in the hot sun for a
towel to dry on a clothes line. :(

Re: Returning to valve equipment for greater reliability?
wrote:
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e a
a

Been there, done that, in the 1950's.  With climate change I don't
think things are getting any better<g>.

Re: Returning to valve equipment for greater reliability?

"hrhofann@sbcglobal.net" wrote:
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   You can watch rust grow, on a slow day. ;-)

Re: Returning to valve equipment for greater reliability?

"Nutcase Kook"
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** Read the above properly -  it says two things:

1. The "correspondent" lives in very damp part of NSW -  there are a  
tropical rainforest areas in the north of the state.

2. SS equipment dies due to high levels of moisture - which is correct.

Almost anything left around in a very damp environment will acquire a flim  
of water  - so needing drying out before use.

Valve equipment left on 24/7 would avoid the problem -  which makes the  
valve life rather short.

Air conditioning the equipment room is the obvious solution.

BTW:

Will NK ever wake up what a jerkoff he is ?



....  Phil







Re: Returning to valve equipment for greater reliability?
wrote:

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It might be possible to reduce the filament voltage when in standby,
thus increasing the life of the tubes.  The "instant on" tube/valve
TV's of the 1960's did that.

In a past life, I designed marine radios, some of which were used in
high humidity tropical areas.  I recall one warranty return where the
insides of the radio were covered with a thick layer of mold growth.
It was gross.  The radio has to be designed to survive such an
environment.  That means vertically mounted PCB's to drain
condensation, self-draining connectors, drain holes on the bottom of
the radio, conformal coatings where possible, fungicides, good
ventilation to remove moisture, galvanic compatibility between metals,
gold connectors, and low impedance designs.  

Sealed boxes didn't work as moist air always sneaks into the box.
Pressurizing the box was the only system that really worked.  Such
hermetically sealed boxes were deemed maintenance problems as they had
to be refilled with dry air after every repair or adjustment.

The really critical part was the low impedance design.  At the time
(1970's) it was common practice to use high impedances to reduce power
consumption.  That was fine if the board was dry, but a little
moisture on the PCB would cause the circuit to go nuts.  While low
impedance designs were not a real solution, it reduced the problem to
manageable levels.  Running the radio immersed in salty water was the
basic test.  It didn't have to meet spec under water, but it shouldn't
fail.  Anything that moved (trimmers, pots, controls, switches,
speakers, meters, etc) were the real problems.

I'm not so sure that heating the radio would have produced anything
useful.  It would have prevented condensation under some
circumstances, but done nothing if the radio were turned off.  Also,
heat tends to promote mold growth.  There was a crystal oven in one
radio.  I would expect the heat from the oven to prevent condensation.
However, when the various radios came back covered with mold, it was
the oven area that seemed to have the greatest accumulation of mold.  

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Yep.  A/C drops the humidity level.  The trick is to not create any
situation that condenses moisture.  That's not easy.
<http://en.wikipedia.org/wiki/Dewpoint

There is a certain fascination with tube/valve equipment.  However, I
would not want to carry a tube type cell phone, calculator, or laptop.
Once we embark down the road toward miniaturization and increased
component density, it's difficult to turn back.  Might was well make
the best of the unreliable junk we have today as the tube/valve
alternative is unlikely to fit or function.

--  
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Returning to valve equipment for greater reliability?
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flim


The problem is in Nimbin , NSW, Australia, with loads of river water around



Re: Returning to valve equipment for greater reliability?

"Nutcase Kook"
 "Phil Allison"
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** ROTFL  -   Nimbin ???

The place is chock full of dope smokin' hippies !!!

And it is semi tropical too.

http://en.wikipedia.org/wiki/Nimbin,_New_South_Wales

Trust NK to have a contact there.



...  Phil  



Re: Returning to valve equipment for greater reliability?
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I worked inside Cheyenne Mountain, Colorado in the mid-1960's on the
military installation there.  It was in the early stages of
construction, the building inside the hollowed-out mountain was
constructed, but the mountain itself was still dripping moisture onto
the building and the air exchange system was not operational yet.

Humidity was 98% or so, at about 60F.  There was mold growing on all
the electronics in the telco products that I was trying to debug.  The
gold-plated pwb circuit pack connectors even had mold growing on the
contact fingers.  Needless to say, the connections were not reliable.
Fortunately for the USA Defense System, they did get the humidity down
and the communications equipment went on to become reliable.

Re: Returning to valve equipment for greater reliability?
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flim

I worked inside Cheyenne Mountain, Colorado in the mid-1960's on the
military installation there.  It was in the early stages of
construction, the building inside the hollowed-out mountain was
constructed, but the mountain itself was still dripping moisture onto
the building and the air exchange system was not operational yet.

Humidity was 98% or so, at about 60F.  There was mold growing on all
the electronics in the telco products that I was trying to debug.  The
gold-plated pwb circuit pack connectors even had mold growing on the
contact fingers.  Needless to say, the connections were not reliable.
Fortunately for the USA Defense System, they did get the humidity down
and the communications equipment went on to become reliable.

+++++

If you include interpretting flocks of geese as incoming Russian missiles ,
and going to DEFCON whatever , as reliable.



Re: Returning to valve equipment for greater reliability?
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 ,
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I only said the communications equipment (AT+T four-wire switches)
became reliable.  All the other "stuff" was not in my baliwick.

Re: Returning to valve equipment for greater reliability?
It seems an equivalent to trying to use equipment stored in sheds in the
otherwise more equable climate of the UK.
Corossion of switch contacts, mould growth from condensation and
consequential extraneous partially conductive tracks. Older equipment had
more resilient contacts materials and generally bigger dimensions, seems to
make them more reliable in such situations



Re: Returning to valve equipment for greater reliability?

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Valve equipment becomes thoroughly warmed and is usually designed to
have a good air flow through the casing; this will dry it out and
prevent tracking and corrosion if it is used regularly.  

Because high voltages are involved, good valve equipment is designed
with long tracking distances and good insulating materials (big
tagboards and ceramic or P.T.F.E. standoffs).  Transformers on good
valve equipment are usually potted or oil-filled.  Cheap valve equipment
with open transformers, printed circuits and small track clearances is
just as vulnerable to tracking and corrosion as modern transistor
equipment.  

Fully-sealed transistor equipment should, in theory, be just as reliable
as good valve equipment; but if the sealing is the slightest bit
imperfect, the wet will get in and stay in, causing worse conditions
than if it wasn't sealed at all.  This sort of kit will then be less
liable to recover than the equivalent valve kit because it will never
warm up enough to dry out.  A small contact heater would be one possible
answer; it could operate permanently, so as to keep the casing a few
degrees above ambient and help to prevent further condensation.


--  
~ Adrian Tuddenham ~
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