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Break Time
- Thread starter albusark
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Mr Wizard~! What a legend!
More relevant today than ever~!
Super nostalgic...
Edit: Nice vintage tube type Tektronix oscilloscope...
Beautiful trace, All other scopes can BOW DOWN~~!
More relevant today than ever~!
Super nostalgic...
Edit: Nice vintage tube type Tektronix oscilloscope...
Beautiful trace, All other scopes can BOW DOWN~~!
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albusark
Dynaco Fan
In today's break time selection, we see ladies build some very beautiful amplifiers. The guy being interviewed about construction calls capacitors condensers first, a clear sign that he's been busy reading century old sacred scrolls and is a true Radiotron designer. The test stations use incandescent light bulbs as a dummy load, limiter and power indicator. Interesting 2 150w bulbs in parallel would be about 48 ohm. Pretty neat wattage test system, upon further research it's called a lamp load bank.
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Here is a similar one from NASA. I found it at a military surplus store in Orlando back in the late 90's;
albusark
Dynaco Fan
MAC'S face wore a broad grin as he
walked into his service shop; and
when Barney, his assistant, saw
this, he immediately put aside the pro-
pane gas torch he had just lit and
challenged:
"OK, what's so hilarious ?"
"After lunch," Mac explained as he
started putting on his shop coat, "I
stopped in at Paul's shop to see if he
wanted to go with us to that color TV
meeting tonight. A customer entered
the door with me and asked Paul, as
a special favor, to do a hurry -up job
on a little transistor radio he had with
him so that he might take it along on
a trip. Paul -maybe wanting to im-
press me a little -said, Sure, come
back in an hour and it will be ready:
"Now I had that same model in here
a couple of weeks back; so I stuck
around to watch the fun. The receiver
is in an all -metal tubular case with
two metal caps on the ends. I could
hardly keep a straight face as I
watched Paul turning that receiver
over and over, ever so casually, trying
to figure out how to get into it without
revealing he didn't know. Finally he
had to give up, just as I did, and look
at the service data. When he read
aloud the instructions for removing the
chassis from the case, his face moved
a shade nearer purple with each step
and his voice went up about one octave
and six db in volume. I couldn't blame
him for these were the steps: 1. Re-
move cap from speaker end of cabinet;
2. Unsolder wire attaching cap to
chassis bracket; 3. Straighten metal tab
holding speaker grille to cabinet; 4.
Remove metal speaker grille; 5. Lift
out speaker and unsolder two speaker
leads; 6. Remove volume control knob;
7. Remove tuning dial screw and tun-
ing knob; 8. Remove screw near tuning
shaft; 9. Remove screw from cap on
tuning end of cabinet; 10. Slide chassis
about '/z" toward tuning end of cabinet;
11. Unsolder three connections from
loop antenna to circuit board. Be care-
ful to observe color coding of loop
wires; and 12. Continue sliding chassis
from cabinet.
58
"Of course this left him with the
chassis free of the case but discon-
nected from the speaker and the ferrite
core antenna; so these had to be re-
soldered and the dial knob and tuning
knob replaced before the set could be
turned on and checked. The joker was
that the antenna was securely fastened
in the heavy case, and the leads from
this antenna were thin, fragile wires
barely an inch long. With them con-
nected, to turn the chassis -board over
you had also to turn the case and the
dangling speaker at the same time -a
feat practically impossible to perform
without breaking off one or more of the
leads. And of course all these steps had
to be repeated in reverse to put the
thing back together. As you know,
Paul's not noted for patience; and he
was fit to be tied when I tiptoed away.
He swore he was going to show the
owner how hard it was to service and
then suggest that he take it back to
the guy who sold it to him and let that
guy enjoy working on it."
"Can't say I blame him," Barney re-
marked with a sympathetic grin. "That
set sounds like it was built to be
thrown away when something went
wrong. The sooner manufacturers get
it through their heads that when they
turn out a receiver especially difficult
to service they are automatically re-
cruiting a whole bunch of enthusiastic
knockers for their products, the better
it will be for them, for the service tech-
nicians, and for the mutual customers
of both."
"OK," Mac said, "but get down off
your soapbox and tell me what you're
doing with the torch -besides carrying
it, of course."
"When I carry a torch for a dame,
that will be the day!" Barney boasted.
"I was checking on something I read
in this book," he went on as he nodded
to a brown book with the title "Solder"
in big yellow letters across its front.
"Clifford L. Barber, research director
of the Kester Solder Company, says in
there you can melt ordinary table salt
by heating it to a temperature of 1488°
F., but you can also dissolve it with
water without the use of any heat.
Watch this."
Barney lit the torch 8nd held the
point of the little blue flame on a
spoonful of salt heaped on top of a
metal plate. In only seconds a puddle
of completely clear liquid formed in a
crater of the loose salt. Barney turned
off the torch and poured a little water
into the bottom of a glass containing
another spoonful of salt. In a short
time the salt dissolved and the glass
contained only a clear liquid.
"Interesting," was Mac's comment,
"but what's that got to do with solder-
ing ?"
"Mr. Barber is making the point that
metals, just like table salt, can be
melted by heat or chemically dissolved.
When we join metals by melting them,
as in welding or brazing, we have to
use lots of heat; but when we soft -
solder them together, we need just
enough heat to melt our solder. The
molten solder actually dissolves the
surfaces of the metals it touches just
the way a little water brushed on a
block of salt would dissolve that sur-
face."
"Now hold on," Mac said, showing
deep interest. "Let me get this straight.
You mean to tell me that soldering is
actually a chemical operation ? That
we just use heat to convert solder to
the proper form for doing its chemical
job ?"
"That's right. Suppose we lay a cop-
per and a brass wire together and flow
melted solder over the joint. This hot
solder flows between the junction of
the two wires and dissolves a bit of the
surface of each wire. The dissolved
copper and the dissolved brass combine
with the solder to form a thin film of
alloy that is not solder, not copper, and
not brass; but an alloy of all three."
"Well I'll be darned!" Mac exclaimed.
"Here I've been soldering all these
years without realizing exactly what
was happening when I pulled the trig-
ger of the solder gun. I guess I had
some sort of fuzzy notion that the two
wires were kind of stuck together with
a sort of super metal adhesive of good
conducting properties. Now I under-
stand that a well -soldered joint is ac-
tually a continuous metal union. Does
Mr. Barber come up with any other
little goodies ?"
"Yes; hear this : lead melts at 620 °F.
Tin melts at 450 °. If you start adding
tin, a little at a time, to pure lead, the
melting point falls steadily until you
reach 63 parts tin and 37 parts lead
by weight. This mixture melts at 361 °.
And if you start adding lead to pure
tin, the melting point of the mixture
also goes down from the original 450°
figure until you reach that same 63/37
mixture and that same 361° tempera-
ture. This combination, which marks
the lowest melting point of any tin /lead
mixture, is called the eutectic composi-
tion.
"The eutectic alloy goes sharply and
immediately from a liquid to a solid
state, or vice versa, as you cross the
361° temperature boundary. This is not
(Continued on page 128)
ELECTRONICS WORLD
Mac's Service Shop
(Continued from page 58)
so for other tin /lead combinations.
Those containing substantial amounts
of both tin and lead become mushy or
plastic at 361° all right; but the tern -
perature at which they become corn -
pletely liquid depends, as we have al-
ready seen, on the precise tin /lead
ratio. The temperature span between
where a solder softens and where it be-
comes completely liquid is called its
plastic range. A 40/60 composition -the
first number mentioned is always tin -
starts to soften at 361° and becomes
completely liquid at 460 °. The plastic
range of 50/50 solder lies between 361°
and 414 °; that of 60/40 solder between
361° and 370°."
"It seems to me that 63/37 eutectic
a mixture is the ideal solder. It melts at
minimum temperature and sets
quickly. So how come the 40/60 com-
position is used in radio work ?"
"Economics. Because of the word 'tin
can' --which is really a steel can with
a very thin tin plating- -most people
think tin is cheap. It's not. In fact it
costs about six times as much as lead.
In radio work we're not concerned with
the little extra heat needed to melt the
40/60 solder; so, since it makes just as
good a connection for all practical pur-
poses as the eutectic composition and is
less costly, it's the one used. If we were
soldering pewter ware and had to be
careful not to melt the stuff we were
soldering, we'd use 60/40 solder. On the
other hand, in filling in car fender dents
where we had to wipe the solder on and
shape it before it cooled, we'd likely
use a 15/85 solder with a plastic range
of almost 200°."
"My, you are full of information!"
"Oh I know lots more," Barney
boasted. "For instance, I know the flux
in solder does three jobs: (1) removes
tarnish or metal oxide, (2) prevents
other oxide from forming while the
metal is raised to soldering tempera-
ture, and (3) lowers the surface tension
of the molten solder so it can wet the
metals and penetrate their pores, as it
must. Resin fluxes, of course, are the
only ones generally recommended for
electrical use.
"And finally, I know the strength of
a soldered connection lies in the thin
solder film -preferably about .004 -inch
thick -in which the alloy action be-
tween the metals being soldered to-
gether takes place. Once this film has
been formed, adding more solder is use-
less waste."
"Seriously, Carrot Top, I'm proud of
you for coming up with all this dope,"
Mac said. "I've read dozens of articles
on How to do a good job of soldering,
and I think we both can make a respec-
table solder joint; but you have told me
a lot I didn't know about the Why of
soldering. And I have always been con-
vinced that until you have mastered
both the How and understood the Why
of a thing, you can't say you know it."
Electronics World - 1960 May Issue
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albusark
Dynaco Fan
Today's break time is a look at the concept of impedance, or resistance in terms of alternating current, from the AT&T archives. A great explanation of matching an amplifier to a set of speakers. Who knew that our ears have impedance matching bones? Maximize energy transfer across unlike media.
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