[R-390] R-390A Cost Reduction and Improvements (was dead horse Hi)
Barry Hauser
Barry Hauser <[email protected]>
Tue, 10 Jun 2003 08:39:57 -0400
Well, Jim, there's more than one way to read the product brochure. As far
as beating dead horses is concerned -- preferred here as beating live ones
would be cruelty to animals. ;-)
Let's review, maybe one last time ... (right)
> For what it's worth, the Collins Cost Reduction Project Document available
> at http://www.r-390a.net/faq-refs.htm identifies the following apparent
> "improvements" investigated for the R390A "A model" as compared to its
> predecessor (R-390). With these improvements, which model would you want?
Well, let's see ...
>
> ** B+ filter improvement - Reduction of receiver temperature caused by
> location of the type 6082 tubes, reducing the cost of the B+ filter.
Getting that heat out of there was worthwhile. Can be done with a muffin fan
or the 6082's can be reversibly solid stated out.
> ** Added a VR tube to get the required stability from the VFO and crystal
> oscillators.
That was necessary because regulation was inadequate without it, so tossed
in a common VR tube as used in SP-600's and many commercial rx's. Not an
enhancement, but a "fix" to a "mod".
> ** Mechanical filter designs incorporated for improved selectivity -
> although phase nonlinearities did impact DF performance;
Latter day evaluation -- yes, better selectivity for SSB, but introduced
ringing, and more important, apparently prone to wear out and break down
after 40-50 years. Expensive to replace.
> ** Improvements in accessibility, reliability and performance;
That's a broadside -- yes & no. Helps if you ignore introduction of
Sprague's latest wonder "Black Beauty" line of molded paper caps,
hermetically sealed to last forever. Original "non-A" seems to have less in
the way of cap failures 50 yrs out, and the failures on the BBOD's probably
started much earlier, but still after the warranties expired. Mixed bag.
> ** Savings resulting from elimination of the squelch facility and remote
control;
That's not an improvement. Space was reserved for a retro-fit squelch under
principles of CYA, blowing $4 of the $14 savings.
> ** Repackaged power line filter;
Again, a simpler one and there was a tradeoff. Also the power connection
arrangement is sub-par compared with many mil sets and downright
unacceptable. Ambigous hookup of AC ground wire with grounded cordset, risk
of shock/shorting out of power if cover left off or bent, no integral strain
relief, allows for improper hookup of hot vs neutral. Should have retained
3 pin round connector. "Improved" version probably wouldn't qualify for UL
approval.
> ** Tuning control stops of improved design;
Part was retrofitted to production non-A's. Correction of defect with
better 10-turn stop.
> ** Crystal oscillator redesign to reduce/consolidate crystals - A new
> frequency scheme permitted a greatly simplified mechanical construction
and
> gearing,
Not so great: Overuse of smaller number of crystals. While "a diamond is
forever", an oscillating piece of quartz is not. Original design
distributed use over more xtals, and consequence of a crystal failure would
take out fewer bands. Also, crystal mounts/contacts are inferior in
"improved" set. Contact area is not as solid, prone to mild oxidation,
intermittents, etc. (40 yrs out, anyway.) That and gear train = mostly
cost reduction, not much improvement, if any.
> ** RF and variable IF coil redesign to improve tracking;
Maybe, but cheaper mounts and connectors. Thin pins vs. substantial
"mini-banana". However, standardization on a common ferrite core rather
that custom matched powdered iron IS an advantage to the "A". (Color coded,
hand tweaked iron powder slugs were apparently the means of handling
tracking problems in the non-A.)
> ** Savings resulting from elimination of the 3500 cps low pass AF filter,
> retaining the narrowband filter.
No AF filter switch.
> ** Mainframe redesign for cost and weight reduction.
I dunno -- gotta go weigh a couple of samples. What's weight
difference - -a couple of pounds at best? Again -- cost reduction. The
laminated side panels of the original were not worth the expense and flexed
more than the heavy aluminum ones on the A. The ability to drop the front
panel without removing the handles (on the A) is also nice.
> ** Eliminated need for hum balance control;
Fell out of dropping electronic regulation. What's a pot cost? Less
"tinker value" ;-)
> ** VFO end point adjustment was made more accessible. In the R-390A;
Seems most PTO's have to be pulled to take off a winding or do some other
internal work anyway.
> ** Holes were provided in the gear plate so that this adjustment could be
> made without removing the VFO or RF units.
Probably one of the reasons that guy dubbed the R-390 NON-A "a man's radio".
Not for lazy wuzzes.
> ** Simplified design and improved the performance of the gear train and
slug
> racks;
Original, though more expensive, was more substantial. I suspect the real
reason that there was no autotune version of the "A" model is that the gear
train was not up to the additional stress of motor drive. They did
introduce lateral adjusters for slug mounts on slug racks - maybe to
accommodate wider manufacturing tolerances.
> ** Redesigned RF module to remove an RF amplifier stage (for cost
savings),
> put mixers on AGC control, use 6DC6 tube for RF amplifier, etc. - probably
> the most controversial change, next to mechanical filters.
Secton on RF module changes is difficult to follow. Seemed to be a lot of
fixing and patching to compensate for dropping one stage.
> ** Calibrator using a 200 kc crystal was built and tested. In comparison
to
> the former model using a 1 mc crystal, reliability was improved and
harmonic
> out-put increased.
Also mentioned difficulty of getting suitable 85 C degree xtal -- "solution
appears in sight".
> ** Where possible tubes were replaced by more rugged equivalents.
I suppose, but I think you can retrofit most of the better version if you
want.
You skipped the part about "VFO stability". Sounds like they had to make
the endpoint adjustment more accessible due to difficulties.
> ** Improved antenna relay provided to overcome poor attenuation in
original;
Some unclarity on this re: attentuation at higher frequencies. I forgot --
do non-A's have the selenium rectifier -- added to run the relay on DC?
> ** Changes in mechanical construction were also made, such as the closer
> attention paid to electrolytic corrosion, the new means for chassis mtg.
and
> the radical power supply unit redesign.
Fair dose of smoke & mirrors here. I see a great deal more electrolytic
corrosion on R-390A's than the predecessor. Don't see where mini-coax and
MB connectors are an improvement over beefy standard BNC's and good thick
coax cable. Most of the mini-coax has deteriorated except maybe the teflon
covered type of the '67 EAC's. MB connectors complicate test hookups
requiring adapters.
Finally ...
You have to read the whole thing -- between the lines as well. The main
benefit to us now is that they found a way to "cost reduce" the R-390,
paving the way for much higher production of the R-390A so many survive.
However, just looking at the construction design differences, the full
amount of cost savings is not all that apparent -- the R-390A was still very
mechanically complex. Some cost reduction elements were really minor --
like dropping the squelch and making it optional. After allowing for the
squelch mounting plate in the "A", the net reduction was placed at $10.
Saved some change by eliminating tools, tube pullers and pin straighteners
off the back panel, etc.
I suspect most of the cost savings was achieved through pencil sharpening
and more aggressive RFB's for components and manufacturing over a wider
group of prospects, not just Motorola and Collins plants.
Don't forget, the cost reducing elements had to overcome the fixed
re-engineering and retooling costs -- "We'll make it back on volume."
There is one other "business thing" I will share with you. If you've been
selling an item to a client for, say $100 a pop and the client comes back to
you and says "Can you do any better? We'd like to order more of these, but
they're too costly." Unless you're an idiot, you do not come back and say
"OK, how about $75?" for the same item. You have to change it and take some
things away or find some way to rationalize the price break ... or, what
does that imply about your prevous price-points if you don't? I have no
doubt that was part of (not all of) the re-design process, but it's a part
that does not get documented, much less discussed out of school by anyone
intending to remain employed in a particular industry. It's business, it's
only business. Fortunately, and to the Collins group's credit, they managed
not to screw up the radio in the process. A lot of products don't survive
"cost reduction" and re-bidding very well, let alone design by commitee.
As for which version is a better one now -- 40-50 years later? It depends
more on condition of the individual unit, including any
restoration/recapping that's been done as well as personal preferences --
not to mention pot luck of what you come across at what price.
Gotta go put the dead horse back in the freezer.
Barry