In article , Al
writes:

If your design criterion is that the equipment be field repairable with
readily available parts, then so be it. I have no argument with that!
But in the high-reliability military electronics world in which I worked
in the late 60's, that was not possible.

In the late 1960s I was working in both commercial, space, and
military electronics. Only the space electronics (unmanned space-
craft done at Electro-Optical Systems, EOS, in Pasadena, CA, a
Xerox division) was there traceability to that extent, plus the "JAN
TX" or tested-extra solid-state components. That was with reasonable
logic since no company would pay per diem for in-the-field space-
craft repairpersons... :-)

I might note that the little labels used to mark the components were
of a selected brand...to avoid outgassing in vacuum of space and
thus coating some other spacecraft instrument or sensor. Some
have called such a practice "braindead procedures by NASA" but
those people are themselves braindead for not thinking through for
operating in a very different environment.

Since that time I've been involved in a lot of other DoD electronics
and have never seen that level of traceability except in certain
prototypes and then used solely for development testing. NASA
man-rating specs - not Mil Specs unless called out for common
types - required screening and traceability for a very good reason
that humans were aboard those spacecraft (STS or "shuttle").
Astronauts shouldn't be required to get down to the PCB level and
unsolder bad components and resolder new ones in microgravity
for one reason. Another reason is that they can't GET to a part
such as the ignitor of an SSME (Space Shuttle Main Engine,
built at Rocketdyne Division of Rockwell International in Canoga
Park, CA, - now a division of Boeing Aircraft). That ignitor was
often called a "spark plug" in-house but was really a redundant
astable multivibrator turned on remotely and a driver for an
external arc gap...the entire "ignition system" in one extremely
clean (had to work in pure oxygen environment) little unit that had
to work just fine in vibration you couldn't possibly imagine.

Much military radio and electronics equipment bears something
resembling screening markings on modules but any research into
that will show they are merely in-house or depot markings for ID
and other things, not traceability. If you see the insides of an
AN/PRC-104 HF transceiver or an AN/PRC-119 VHF FHSS
transceiver, you will see what I'm talking about.

Would you believe that one
printed circuit card, 4 in by 6 in, was needed just to implement 4
flip-flops using descrete components.

That's not at all strange for the late 1960s. Integrated circuits
weren't there to use, and had only begun to be Mil Specced.
Those were new from Texas Instruments and still the old DTL or
Diode-Transistor-Logic.

The IBM 360 and RCA Spectra 70 used discrete-transistor PCBs
in the 1970s. IBM didn't go into TTL ICs in a large way until the
IBM 370 VM and production starting around 1975.

Each component, yes even a carbon
composition resistor, had a serial number on it. Why? So it could be
traced back to the lot from it which it had been selected if it failed.
And boy, did those components have to be reliable! So that's why the
military specifications with their "strange" component markings were
invented. Expensive? Lordy, lordy! I was very shocked one day when I
requisitioned a capacitor from stock to compare to a rejected one. The
price for that unit, a precision paper mylar cap. was $100 - in 1970's
dollars! I almost fell out of my chair! And now you can buy stuff like
that, surplus, for just pennies on the dollar...and with their strange
markings.

I'm going to challenge the veracity of that claim due to "having been
there, done that," and only seeing that in NASA electronics.

Also, I have yet to see any "surplus" spacecraft, including the
engineering and test models that never flew.

Back in 1974 I and a co-worker were stuck in Galveston, TX, for an
RCA Corporation field test. We visited the Manned Space Flight
Center in nearby Clear Lake and did a walking tour on a Sunday,
unescorted as was the norm on Sundays there. I wanted to show
the friend the Solar Wind Spectrometer instrument built for the
ALSEP (Apollo Lunar Surface Experiment Package) in 1967. I had
handled all of the SWSs when they were built. All of the ALSEP
modules - except the SWS - were arranged around the "left-over"
Landing and Ascent stages in the lobby. I snagged a docent and
asked about the "missing" instrument. She went off and returned,
said "sorry, it is still being used in a lab experiment." Seven years
later and it was still working...after having gone through some tough
environmental testing on earth.

NASA manned or unmanned electronics is subject to the maximum
in traceability. Military fielded electronics has had traceability
limited to specific lots identified through records and specified
percentage sampling tests on those lots. Samples may be tested
to destruction depending on the Mil Specification. All that TESTING
effort is what drives the parts cost up AND having to package spares
in extra-special protection envelopes and containers since they may
be sitting waiting in some terrible environment somewhere in the
world. World War 2 production and logistics taught the U.S. military
much about needing spares and how to ship and store everything.
USA has always been darn good about logistics and supply and
has been successful at it.

To those folks who want to sneer at "military intelligence," fine.
Nobody is forcing them to like military electronics or the military.
Let them build things for room-temperature environments using
surplus CB radio parts or those from TV sets. However, when
those also sneer at little things like nomenclature about high quality
stuff available surplus at cut rate, it does warrant a strong response.

Roy Lewallen had the succinct response. :-)

Len Anderson
retired (from regular hours) electronic engineer person