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Archive-name: antiques/radio+phono/faq/part8

Rec.antiques.radio+phono Frequently Asked Questions (part 8)

Revision  Date            Notes
1.0    Oct 28, 95    New section

Part 8 - Tools and Test Equipment
------------------------------------------------------------------------------
FAQ editor: Hank van Cleef.  Email [e-mail]

This is a regular posting of frequently-asked questions (FAQ) about
antique radios and phonographs.  It is intended to summarize some common
questions on old home entertainment devices and provide answers
to these questions.

[faq editor note Oct.'95. This is a new section, which includes material
previously covered in other sections, as well as new material].

This section of the FAQ is divided into two parts: tools, and test
equipment.  The section on tools is intended to be general, covering
tools suitable for working on acoustic phonos and other mechanical
devices as well as electronics.  The section on test equipment is
primarily electronic.

TOOLS:

If you are going to work on anything yourself, you will need some hand
tools.  Keep in mind that "tools" and "trades" go hand-in-hand.  Most
tradespeople are expected to own their own hand tools, and the best
sources of good tools are those that sell to crafts trade users.  Anyone
whose livelihood depends on use of hand tools will tell you that there
are two kinds of tools:  good tools and no tools.  A cheap tool is worse
than no tool.  It will cost you some money to buy a suitable assortment
of proper hand tools for various jobs.  Good tools properly used will
last a lifetime, and you'll get a good return on the investment.  I have
tools that I bought over forty years ago that still work "like new."
Craftsmen (and women) who use tools professionally will tell you that
cheap tools are "knucklebusters" (and worse).  There is no substitute
for having the right tool for a job.  Trying to get by without proper
tools for jobs, or with cheap tools, you'll damage the work and hurt
yourself.

Take the time to learn how to use your tools properly.  A quick trip to
the library will produce books on various crafts trades that include
selection of tools, use of tools, and maintenance of tools (such as
cutting tools) that require maintenance.  Talk to crafts people in
various trades.  The automobile mechanic may tell you that Snap-On tools
are overpriced and frosting on the cake, but that same mechanic buys
every week from the Snap-On truck.  And the welder will question whether
Linde double-diaphragm gas regulators are really needed, but that's
probably what he is using for gas welding.  There is an old adage that
"the poor workman blames his tools."  Develop your skills in using good
tools, and you'll get good results.

One point of etiquette:  If you are talking to a crafts person, don't
charge over to his/her toolbox and start looking around.  Ask permission
before handling someone's tools.  Most crafts people will gladly show
you what they use, and tell you why they value particular tools.

Q.  What do you consider basic tools for working on old phonos or
radios?

A.  There are a number of common small tools for working with any small
device.  These are:
    a.  Flat-bladed screwdrivers.  You will need an assortment of
these in various sizes.
    b.  "Phillips" cross-point screwdrivers.  The also come in
various sizes.  The most common is #2, but you will also want #1 and #0.
The tips on these wear out, and the only solution for this is to buy
good quality replacements when the tip becomes worn.
    c.  Hex socket keys, commonly called "Allen Wrenches."  Start
with a kit that has the common sizes, from .050 through about 1/4 inch.
The most common are the "L"-shaped keys.  They are also available in
screwdriver shanks with straight bits.  Once again, these wear out.  You
can grind the worn tip off one to give it more life, and buy the various
sizes individually.  Most people working on old electronics have several
.050, 1/16", and 5/64" keys as these are the ones most frequently used
in small work.
    d.  Socket wrenches.  A 1/4 inch drive set in a box, with
ratchet, screwdriver handle, and extensions, is a good choice.  You can
also buy nut drivers, which are screwdriver shanks with socket tips.
The "six point" (or hex) sockets are best unless you actually need to
work with 12-point hardware.  Most commonly used are 1/4", 5/16",
11/32" nut drivers.  3/8", 7/16", and 1/2" are used on binding post,
switches, and potentiometers.  For these, a ratchet and deep socket is
best.
    e.  Box and end wrenches.  These come in a variety of styles.  A
box wrench has a hex shape at either end, two different sizes.  An "open
end" wrench has fork-shaped tips with parallel sides, also made with
tips at both ends, two different sizes.  A "combination wrench" has an
open end at one end and a box at the other, same size at both ends.  Box
wrenches are generally made with the box ends offset from the wrench
shank.  Open end and combination wrenches don't generally have this
offset, but the box end of a combination wrench is generally set at a
small angle to the shank so that the wrench shank has clearance above
the work.   Which is best?  Most people use all three types in their
work.  The open end wrench will tend to spring and round off the corners
of the hardware if a lot of torque is required, and most people feel
that the box ends should be used except where clearance requires use of
the open end.  Note that there are specialty "tubing wrenches" for use
with hex fittings on tubing.  These are box sections with a cutout to go
over the tubing, to get a good grip on the fitting.   These should be
used only on tubing fittings, not as general wrenches.

    f.  Pliers.  These come in a bewildering variety of sizes,
shapes, and tip types.  Many people also try to use them instead of
wrenches or other more suitable tools, which is not good.  Pick pliers
for pliers applications, and get the right tools for other hardware
tasks.  For small work, needle-nose pliers get steady use.  You will
want to have a set with a very long narrow set of jaws and another that
is larger and more blunt, generally called "round nose."  Both have long
parallel jaws and a rounded tip cross section.  A pair of "duck bill"
pliers is also quite useful.

    The common slip-joint "gas pliers" can be useful, but many
people consider them a tool that works poorly on a variety of tasks and
not very well on any of them.  For large work requiring sturdy jaws, a
set of "Channellock" (TM) pliers is much better.  The originals were
made (and patented) by Channellock in Meadville Pa., originally named
"Champion Dearment."  Get a set that have the interlocking channels for
adjustment.

    g.  Diagonal pliers, wire cutters, side cutters, etc.  These
names are all applied to plier-type tools with cutting tips.  You will
want a small set for cutting wire.  Some of these are made with the
cutter tips ground all the way to the very end, which is useful for
nipping wire loops on old electronics terminals.  They are intended for
cutting soft materials, like copper wire, and can be damaged by trying
to cut hardened steel with them.

    h.  Hemostats:  These look like scissors, but have duck-bill
tips on them and a latching mechanism on the handle.  Originally used in
medical work for clamping off blood vessels.  They were used in
electronics as "heat sinks" for soldering germanium semiconductors, to
bleed the heat off the lead.  Also valuable for use in applying clamping
pressure to thin sections.

    i.  Magnifying lenses and eye protection.  You will want some
sort of magnifying glass, jewellers loupe, or bench magnifier, for
examining things in detail.  A 5X magnifier is a good choice for most
work.
    Always have eye protection when using tools.  If you do not wear
eyeglasses normally, get some safety glasses.  Corrective lenses must be
the "shatterproof" eye protection type, and if you wear corrective lens
eyeglasses, get a pair that is suitable for close work that has
shatterproof lenses.   Contact lenses do not provide eye
protection---have something in front of them.

    j.  If you are going to do really small work, like meter
movements, a set of jeweller's screwdrivers is a good investment.
Brookstone sells a kit in a box that includes an assortment of small
flat-bladed and cross-point screwdrivers, tweezers, small cutting
pliers, and a magnifying glass.

Q.  Where do I get good tools?

A.  You can get them from sources that sell primarily to the crafts
trades.  Most independent automotive jobbers carry automotive tools such
as SK and Herbrand.  Snap-On tools are sold by independent sales people
whose "store front" is usually a step-van type truck (similar to a UPS
or bread delivery truck).  Other brands are also sold by independent
people operating out of delivery trucks.  These people make regular
rounds of automobile and aircraft repair shops, and are often not listed
in the telephone book Yellow Pages.  Look under Snap-On, SK, and
Herbrand in the white pages.  It may be necessary to inquire at an auto
repair shop or two, or at an airport fixed base operator maintenance
facility, to find out when the various tool dealers normally arrive, and
how to get in touch with them.  You can generally arrange a mutual
meeting point with these people, either on their normal route, or by
appointment.  Almost all of them know their tool lines and their uses
extremely well, and can advise you on what to buy, knowing what uses you
plant to make of them.  Be prepared to spend money.  Most electronic
distributors carry good selections of specialty tools for electronics
work.  The best sources are those to sell to the trades.  Don't look for
prices, look for quality.  Those who sell tools will sell to an
individual for the same price as they sell to crafts people in the
trades.

Keep in mind that good tools are, by and large, not "consumer items"
that you'll find in "low price" type stores, such as K-Mart and
Wal-Mart.  The one exception is Sears, Roebuck, who have historically
sold good quality tools under their in-house "Craftsman" name.  I have
recently heard reports that Sears quality has become less reliable.
Also, while Craftsman tools were historically good tools, there are a
good many tools that are much more refined, and are worth the extra
money in productivity.   SK, Herbrand, Blackhawk, Krauteur (pliers in
particular), and Channellock are all excellent in the USA.  Snap-On is
the "Rolls Royce" in automotive type tools, and generally cost more for
tools that may or may not be superior to some of the other brands, but
you'll find all of these brands in a mechanic's toolbox.


Q.  What about soldering equipment for electronics work?

A.  All of the manufacturers that use solder to connect electronic
components run "solder school" for new employees.  Electronics soldering
is not the same as soldering pipes in plumbing or doing auto body lead
work.  There is only one way to learn, and that is to do it.  You will
need:

    a.  Soldering iron.  A Weller or an Ungar "solder station" with
a 35-50 watt "pencil" iron and thermal control in a soldering iron
holder is best.  If you are going to unsolder components directly
soldered to a chassis, you will need at least 50 watts, and maybe a
larger 100 watt iron.  Do yourself a favor and buy a good soldering
station.  It will cost more than a cheapie Radio Shack iron, but you
will find that the tip stays in good condition a lot longer, and that
you do much less damage with heat, using a good iron.  The solder
station holder provides a place to put the iron down that is safe, a
real "plus."  Also, buy an iron with a plated iron tip, or get one for
it.  There is just no way to keep a copper tip well-tinned for this type
of work, and solder eats away the copper, ruining the tip after a
while.

    b.  Solder.  Kester or similar ROSIN CORE solder is sold
specifically for electronic use.  It is "eutectic" solder, that is, 37
percent lead, 63 percent tin, which melts at the lowest temperature.
Don't use 60-40 plumber's solder, which is 60 percent lead.

    c.  Small tools for use when soldering.  You will want some fine
point needle nose pliers, some medium point needle nose pliers, and a
small set of diagonal cutting pliers.  Also, a small screwdriver and a
solder "pick" that has a pointed piece on one end and a v-notched piece
on the other.  Round this out with a solder sucker (a little pump with a
high-temperature plastic piece that you can safely shove into hot
solder, and a button trigger to trip the pump).  Solder "wick" works
well, but remember that when you are removing solder from a 1934 radio
terminal, you are removing 4 or 5 times the amount of solder used on a
modern printed circuit board---use the pump to remove most of the solder
and the wick to remove the rest.

Tin your new iron, and keep the tip well-tinned at all times.  This
means keeping a coat of unoxidized solder on the tip.  The solder
stations come with sponges.  Wet the sponge, and wipe the hot iron on it
to clean off residue.  To tin the first time, just melt some solder on
the tip.  The rosin in rosin core solder is a mild flux---that is,
chemically active to deoxidize and clean the surface so that solder will
flow onto it.  Wipe the iron back and forth on the sponge to distribute
the solder.  When properly tinned, the tip should be shiny with fresh
solder all around back about half an inch.  Keep the tip looking like
this, and you'll eliminate half the problems people have when soldering.

To remove components, heat the old joint until the solder melts, and
remove the solder with the solder sucker.  Bend the old component leads
back, and slide the lead out.   You'll have to keep the joint hot until
you've got the bent-over part of the old lead away from the terminal.
This sounds easier than it is.  You will want to learn to use the solder
pick, small screwdriver, and needle-nose pliers on various joints.  If
the component you are removing is scrap, clipping the lead and leaving a
short loose end often makes getting the loop open easier, and once the
loop is open, the lead can be removed by pushing the wire through the
terminal.  Also, using the nippers (carefully!) to nip the wire loop so
that it will break often helps when removing components.

Watch out what you are heating, and watch out what you are pushing and
pulling on.  That iron is hot and will burn wire insulation, melt
polystyrene (clear plastic coil forms), etc.  Move things out of the way
so you have a clear shot at the joint you are working on.

Don't bend terminals back and forth---they'll break.  The worst ones for
breaking are on the 7 and 9-pin miniature tube sockets, and if you break
one, you get to replace the socket, which is a major task.  Coil form
terminals are not far behind, and most of those old coils are
irreplaceable.  The big terminals mounted on phenolic terminal strips
are fairly rugged, and components fastened to them are a good place to
get some experience before tackling finer work.  On fragile terminals,
once the solder is removed (use solder sucker and solder will to remove
as much as possible), a little judicious use of nippers to cut wires,
and other little tricks you will learn as you go along, to avoid any
stress on the terminal, is the only way to go.

Another trick is to make a cold solder joint.  Just wiggle the lead a
little while the solder cools, and it will stay free.  You can then work
with two hands to get the joint opened up and the lead out of the hole.

When installing new components, run the leads for all new components
going to a particular terminal before soldering any.  Form the leads
into new loops and nip off the excess.  Place the iron against the
terminal and melt some new solder by pressing it against both the iron
and the terminal.  It will melt on the iron first, then into the
terminal.  Don't use too much solder, and make sure that the solder
flows onto all the wires and onto the terminal.  Once the solder has
flowed into the joint, remove the iron and wait for the joint to cool
and solidify.  This is where cold solder joints occur.  A cold solder
joint happens when a lead gets wiggled as the joint is cooling,
preventing formation of a solid bond.  They are generally easy to see,
because the solder ball on the terminal will often be very frosty, and
not have a smooth surface.  They are also very easy to make, and you
should experiment with some scrap---just wiggle the pieces as the solder
is cooling, and you'll get a cold solder joint.  If you've got any doubt
about a joint, reheat it and reflow the solder.

Cold solder joints are the single most common solder defect.  Inspect
your work carefully after soldering, and if there is the least doubt
about the joint, reheat it.  Excess solder and solder bridges (where the
solder flows between adjacent terminals) are other quality
problems---remove excess solder, and inspect carefully.  Many radios
were "unrepairable" simply because of bad soldering somewhere.
Attention to producing the very best workmanship, and close inspection,
will produce quality solder joints----anything less will produce
trouble.

While the people who originally built these radios were very skilled,
you'll occasionally find a cold solder joint or a joint with no solder
at all on a lead that has been there as long as the radios has been
around.  Don't be afraid to inspect, reheat, and reflow a fifty year old
solder joint that looks suspicious just because it has been there for
fifty years.

There are two schools of thought on rosin removal.  You can leave the
rosin on the joint, and most radios were made that way.  However, if you
do want to remove it, isopropyl rubbing alcohol on a Q-tip will melt it
right off.

Q.  I need to solder some sheet metal, and my soldering iron won't melt
the solder onto the metal.

A.  The soldering process for electronics work is conceptually the same
as for sheet metal, but uses small irons, mild fluxes, and eutectic
solder (63/37 or 60/40), which melts from solid to liquid state very
quickly.

For sheet metal work, there are several processes that are used,
depending on the metals to be joined and the strength needed.  These can
be divided into three categories:
    a.  Soft solder, using pewter (tin-lead alloys).  Requires use
of a large soldering iron or a flame such as a propane torch.  May
require strong fluxes and use of 50/50 or 37/63 solder, which has a
mushy state and can be worked with paddles or a damp rag.  Most radio
sheet metal work is done with cadmium plated parts, which will solder
with rosin flux.
    b.  Brazing, which is a similar process, but uses copper or
silver alloys and a much higher temperature than soft soldering.
Requires an oxy-acetylene torch and appropriate fluxes.  The principal
difference between brazing and soldering is that non-pewter alloys and
much higher temperatures are used.  Silver brazing is often called
"silver soldering."
    c.  Welding, which involves melting the metal of the parts and
using a similar alloy as a filler to join the parts together.  This
requires use of high temperatures to melt the metal.  Principal
methodologies are oxy-acetylene "gas" welding, traditional electric
"arc" welding, and inert gas electric welding, such as "MIG" or "TIG."
There are other electrical processes such as resistance, or "spot"
welding.

I mention all of these because you need to recognize where these
processes were used in original manufacture.  For radio work, soft
soldering on sheet metal parts generally involves lead attachment, and
is best done with a 75-100 watt iron, using radio solder and rosin flux.
Don't attempt to repair brazed or welded parts with soft solder if any
strength is required.  While brazing and gas welding are conceptually
simple, most hobbyists do not purchase the equipment necessary, and both
require some experience to do well, particularly on small work.

TEST EQUIPMENT

The most frequently asked questions are about tube testers, and many
people who are attempting to get their first radio working assume that a
tube tester is the first piece of test equipment needed.  This is not
the case.  In a recent discussion between "old-timers" on the boatanchor
list who had worked professionally in manufacturing plants during tube
days, it developed that none of them recall seeing a tube tester in
places like Tektronix, James Millen, or Automatic Radio.  While vacuum
tube (or valve, to the British speakers) faults are historically the
most common faults found in old electronics, most of them can be quickly
diagnosed in the application circuit.  Also, there are many subtle
faults that a tube tester won't find.  We'll discuss tube testers
further down, but will put discussion of other test equipment first.

Q.  People talk about using a "Simpson meter."  I'm tired of hearing
about Simpson.  And what do Simpsons have to do with electronics?

A.  The Simpson model 260, first produced right after WW II, is the most
common VOM (volt-ohm-milliameter) found in both manufacturing and
service establishments.  It is a 20,000 ohms/volt (DC) multimeter, that
measures DC and AC voltages, currents, and DC resistance.  Simpson is
the name of a manufacturer of meter movements, as well as complete
multimeter products.  The Triplett 630-series is a direct competitor,
and some people prefer the 630-NA over the Simpson 260.  Both are still
produced, and cost around $150-175 for the basic models.

A good VOM can be used to diagnose about 99% of the faults in old
electronics if you know how to use it effectively.  It is the first and
most important piece of equipment to have on your bench.  You'll rarely
see a used VOM for sale, because they are workhorses, and everybody who
has one is either using it or has managed to reduce it to junk by using
it for decades in all types of conditions.  There are inexpensive VOM
multimeters for $25-$50 available from places like Radio Shack, if you
don't want to pay the price for a good commercial quality meter like the
Simpson or Triplett.  Either you have a VOM or you need to get one now.

Q.  What other test equipment is "basic" for working on old radios.

A.  For most work, the basic instruments that will do almost anything
are a VOM multimeter, a signal generator, and an oscilloscope.  This has
been true since the mid-1950's, when oscilloscopes that were
sufficiently versatile for general purpose use became available.  There
are a variety of signal generators that can be found in the flea markets
and hamfests.  For radio work, you will need something that produces
modulated and unmodulated signals between the IF frequencies and the
high end of the receiver bands, as well as a suitable audio signal for
testing audio circuits.  A generator capable of generating signals from
100 Khz to 110 Mhz, and a fixed 400 Hz audio tone, will cover the needs
of AM long wave, medium wave (US AM broadcast) and high frequency (1.6
to 30 Mhz) radios, and cover the 88-108 Mhz. FM band as well.

Two items that were very common in service shops in the 1940's, but
which are more-or-less forgotten today are the VTVM (vacuum tube
voltmeter) and signal analyzer, or signal tracer.  We'll look at both
below.

Used test equipment is generally available at very reasonable prices.
Unlike the costs of hand tools and soldering equipment, it is easy to
build up a very adequate bench full of useful items for about $100.

Q.  I saw a Hewlett Packard signal generator at a hamfest, and, at a
nearby table, a Hickock signal generator.  I know that Hewlett Packard
is supposed to build top-notch test equipment, but the Hickock generator
was a lot less expensive, is smaller, and seemed to cover almost the
same ground as the HP generator.  What's the real difference here?

A.  Essentially, the "real differences" are that Hickock equipment was
generally low-price test equipment targeted toward service shops.  HP
equipment was costly, and generally bought by research and engineering
organizations.  As you note, the Hickock unit is smaller.  Look inside,
and you will see home entertainment type construction, with light sheet
metal work, inexpensive components, etc.  Inside the HP box, you'll find
things like huge aluminum castings, top quality components, and more
refined circuitry.  The products may have performed similar functions,
but were designed with entirely different philosophies, and targeted
toward entirely different markets.  One I would call "service grade,"
the other, "laboratory grade."  Generally laboratory grade instruments
were used by highly skilled professionals in laboratory environments.
The service grade boxes were often hauled around in the back of a sedan
delivery or pickup and pretty well beaten up, and weren't expected to
last forever.  The reason you see so much laboratory grade equipment in
the used market today is that it is thirty or forty years old and lived
all its life either in a laboratory environment or in storage in the
back of an test equipment pool area.  Below are some of the brand names
generally associated with the two grades of instrumentation.

    1.  "Service Grade."
        RCA (signal generators, oscilloscopes, meters, tube
        testers).
        Hickock (signal generators, tube testers).
        Supreme (signal generators, multimeters, tube testers).
        Radio City Products (signal generators, multimeters).
        Eico (a broad line of manufactured and kit instruments).
        Heathkit (a broad line, kits only).
        Simpson (multimeters).
        Triplett (multimeters).

    2.  "Laboratory Grade."
        Measurements Corp.  (Signal generators, grid dips),
        Boonton Radio Corp.  (Q-meters, other LC instruments).
        Allen B. Dumont Laboratories. (Oscilloscopes).
        General Radio (A broad line, including RLC bridges,
        signal generators).
        Weston instruments  (meters of all types, standard
        cells).
        Hewlett-Packard (broad line of test equipment).
        Tektronix (Oscilloscopes and related equipment).
        Marconi (British.  broad line of test equipment).
        Philips (Netherlands.  broad line of test equipment).
        Leeds and Northrup  (voltage and current calibration).
        Guildline of Canada (voltage and current calibration).
        Waterman (oscilloscopes).
        James Millen (grid dips, frequency standards,
        specialty oscilloscopes).
        Wavetek (signal generators).


Q.  What about VTVM's?  I notice that you can get a "service grade" RCA
VoltOhmyst or a "laboratory grade" HP or Ballantine unit.  Are the HP
and Ballantine meters really superior to the VoltOhmyst.

A.  I have WV97A and WV98C VoltOhmysts, and HP400D AC and 412A DC
VTVM's.  The meters that get the most use in my work are the WV98C and
the HP412A.  I like the WV98C because it has both AC and DC capability,
and a reasonably good ohmmeter.  It is also much more responsive to
signal changes, and is much easier to use for a lot of service tasks.
The 412A is extremely accurate across the scale, much better than the
WV98C, and has a maximum full-scale sensitivity of 100 microvolts,
compared to the WV98C's 500 millivolts.  It also has a much wider ohms
range, and is more accurate there, too.  It won't measure AC voltages,
and the design cuts off AC response at only a few Hz, so it is slow to
respond to changes.  In short, the tradeoffs are not only construction
quality, but in flexibility.  The WV98C required some component
replacement when I got it, but it is a much better setup for general
service work.  The HP meter needed a light bulb replaced in the chopper,
but was essentially "plug 'n play" and didn't need recalibration.

The HP400D is an "AC meter," and the WV98C has "AC" voltmeter functions.
However, the 400D is a true RMS meter, while the WV98C is peak-reading.
That is a major difference.  If you are looking at the calibrator output
of a Tek scope, which is a square wave, the WV98C reads the peak value,
and you have to read that value on the "P-P" scale.  The 400D reads the
equivalent DC energy value of the square wave, information that is not
particularly useful if you want to see if the calibrator is anywhere
near accurate.  RMS measurements have plenty of value when looking at
something like a class C amplifier.  The 400D was also something of a
bear to get working properly, because it had been "fixed" by someone who
did not know the principles of operation, and who "repaired" all sorts
of things except what was actually wrong with it.  In short, all three
meters have their place on my bench, and in several applications, one
will not substitute for another very well.

One point that should not be overlooked is that the sophisticated
circuitry of a laboratory grade instrument can be a nightmare to trouble
shoot and repair.  The WV98C does not have a chopper with lightbulbs, a
clock motor, and optical switches, which had problems in the HP412A, and
has only a rudimentary power supply, so does not have the regulator
problems that were the actual fault found in the HP400D.

You can get a great deal of good use out of a service grade VTVM over
and above what you can get from a passive VOM.  Input impedance is much
higher, so you can accurately measure things that the VOM can't see.
You can invert the DC sensing and measure negative voltages directly,
and the ohmmeter function has a lot more capability than is available
with a VOM.  While one quickly gets used to the backward-reading
ohmmeter scale on a VOM, I still like the VTVM's forward-reading
ohmmeter.

Q.  What about signal tracers/analyzers.  You mentioned these.  What do
they do?

A.  These came in several configurations.  The fanciest ones were the
RCA "Rider Chanalyst" and Meissner Chanalyst.  Essentially, what they
are is a substitute radio receiver, in sections, that you can use to
duplicate the functions in a receiver under test.   The simpler units
had only a crystal video receiver (i.e., an untuned detector and an
audio amplifier).  The RCA Rider Chanalyst has a built-in signal
generator and VTVM.

The trouble-shooting methodology for using one of these boxes
effectively is to start at the receiver front end, and use the probe to
listen for signal.  Simply trace forward with the probe until you find
where the signal disappears or becomes garbled, and you've found the
area that is faulty.  Instead of reading meters or scope traces, your
ears tell you what's going on.

The RCA Rider Chanalyst was in a self-contained box that could be tossed
in the back of a car, taken out to a customer's home for a house call to
visit a sick Philco Chairside.  Probes, power cord, and even the
instruction manual clipped inside the front cover.  Armed with a tube
caddy, a soldering iron, and an assortment of resistors and caps, the
set could be brought back to life in short order.  Needless to say, the
customer could watch all this, be impressed by the "doctor's" widget box
and bedside manner---and hear for himself (or herself) the walkthrough
that located the trouble.  The smaller units, like the Philco, Sprague,
and McMurdo Silver units, were not all-in-one boxes, but worked with a
signal generator and multimeter alongside.

Q.  I have a chance to get a Tek 535 oscilloscope with some plugins for
a very reasonable price.  Is this a good thing to have, particularly
when you say that oscilloscopes were rare in service shops in the 30's
and 40's?

A.  Grab the scope, if it is working and calibrated, and has had the
selenium rectifiers replaced with silicon (Tek made conversion kits for
this).

There's been some thought given to coming up with a Tek Scope Faq.  Stan
Griffiths published a very good little book (available from Antique
Electronic Supply) on old Tek scopes named "Oscilloscopes: Selecting and
Restoring a Classic."  Both Stan and I worked for Tek, and we've been
holding something of a steady forum on the boatanchors list on the
topic.  In the used market, Tek scopes abound, for quite low prices,
considering what they are.  The most common models are the 545A, 535A,
and 547.  Almost any of the others in the 530-540 line are good scopes
that come back to life quite well and give yeoman service.  The common
plug-ins for these are the CA, K, and G, and you will want at least one,
if not all three.  The 547 requires a 1A1 for full bandpass, but will
work with any of the letter series.  These scopes are big and heavy,
around 65 lbs, and gobble up about 500 watts of power.

On smaller scopes, the 561A with plug-ins is a good scope, although
limited to 10 Mhz bandpass.  The 310 is a little (3" tube) cutie that
can be very handy, although they are somewhat prone to overheating if
you try to run them all day.  I'm not going to try to sum up what is in
Stan's book here.  He has 200 pages devoted to descriptions of old
scopes and plug-ins, and the vast majority of the equipment described is
good for working with radios.  The later 7600 series scopes with the
right plug-ins are also good choices, but tend to be more expensive, and
more difficult to repair.

I'd pick any of these over the 585 (which does NOT work with
letter-series plug-ins unless you have a special adapter), some of the
specialty scopes like the 517, 519, and 502.

On other brands of scopes, Hewlett-Packard tried to compete with
Tektronix for a while.  Some of their scopes, particularly the lower
performance units, were fairly good, and some others were marginal.  The
Fairchild-Dumont 766H was at least the equal of the Tek 547.  However,
so far as I know, they are more or less orphans today, with very few
people having documentation, spares, parts units, etc.

Other scopes?  Most of the others are much lower performance scopes than
the Tek 530-540, and a good many of them are lower quality as well.
Unless you are a scope collector, don't bother with the WWII-era P4
synchroscopes, the old RCA's, or the pre-Fairchild Dumonts.  One
particular group of scopes to avoid is the Lavoie, Hickock, and
Jetronics "Tek wannabe" scopes that government agencies bought in large
quantities.  These, along with "Tek wannabe" plug-ins, are easy to spot.
They look like Tek stuff, but don't have any manufacturer's name on
them.  Identification is by a screwed-on nameplate.  Genuine Tektronix
has the Tek logo, the name "Tektronix," and other very clear markings on
it.  These are, to be blunt, nothing but electronic junk.

My personal preference is for simpler scopes.  I use a 533A or a 310 for
most work, and don't find myself at all hampered by 15 Mhz bandpass
(533A) or lack of a delaying sweep (useful for pulse and digital work),
or a dual-trace setup.  The real value provided by an oscilloscope is in
qualitative graphic displays.  For serious quantitative measurements,
other test equipment is simpler and more accurate, and it takes a good
deal of skill and experience to set up and use an oscilloscope to make
good quantitative measurements.

While you can buy "repairable" Tek scopes and plug-ins regularly for
$10-$50, I feel reluctant to advice the novice to run right out and to
this.  Stan Griffiths has about as much experience working with Tek
scopes as anyone, and I certainly would not want to get into a
productivity contest with him.  Both of us feel that trouble-shooting a
sick scope is fairly straightforward and easy, and we buy "repairables"
and fix them fairly quickly and easily---most of the time.  But a 545
has something like 75 vacuum tubes (I never counted all of them---there
are eight here, ten there, seven more another place, etc.), and someone
who is not familiar with Tek scopes and trouble-shooting methodologies
in general might have a terrible time.  Both of us have bought stuff
and found, when we started trouble-shooting, that someone had been there
before us and "fixed" almost everything except the real problems.  It's
obvious that somebody else tried to fix some of these, and couldn't.
Both of us have specialized test equipment, and both of us know how to
set up a completely uncalibrated scope.  For someone who isn't really
prepared to play "scope wizard," and who wants a solid, reliable scope,
finding someone who knows Tek scopes and who has
clean-working-calibrated units for sale for $125-$150 may be a lot
better bet.

Q.  Ok, I've read through all the blather about meters, signal
generators, and oscilloscopes, and my question was about tube testers.
When are you going to talk about them?

A.  Ok, fair enough.  Roughly, tube testers can be divided up into a few
categories.  (Your FAQ editor is flying somewhat blind here.  I don't
own or use a tube tester of any type, and it has probably been forty
years since I tried to use one.  Dan Schoo has kindly furnished
material on tube testers, which is included after this general
discussion).

    1.  Emissions testers.  These are the type that used to be seen
in drug stores, and the Heathkit "Tube Checker" type of box.  They are
fairly simple, have a heater/filament supply, a "good/?/bad" meter.
They generally operate by connecting the tube as a triode and seeing how
much current will pass through.  Short circuit testing is by applying a
voltage across element pairs and seeing if enough current will pass to
light a neon bulb.

    2.  Transconductance testers.  The best known of these are the
Hickock testers, both the civilian and the military models.  As with the
emissions testers, they are provided with a heater/filament supply and a
shorts test arrangement.   However, they are provided with separate DC
supplies and controls for setting the tube elements at one or more
operating points.  Readout, as with the emissions tester, is on a meter
which indicates plate current.  Most of these have two sets of settings
for the meter readout.  In one mode, the meter reads the current as DC
transconductance.  In the other, the meter reads on a "Good/?/Bad"
scale.  The controls for setting the operating point parameters and
meter sensitivity maybe either potentiometers and switches, or sets of
contacts operated by a punched card.  The type that uses potentiometers
and switches is generally used with a tabular listing (a roll chart in
the machine) of switch settings and readings.  I am not sure how the
pots and switches are calibrated, and how easily one can reset the
operating point parameters, or read current values on the meter, for
taking a series of operating points to plot on a graph.  I haven't seen
any discussion indicating that anyone is using them other than with the
tabular chart values for specific tubes.

    3.  Tektronix 570 Vacuum Tube Curve Tracer.  This is a specialty
oscilloscope that can trace out families of operating curves on a CRT
X-Y display.  The box is provided with a heater/filament supply, two
adjustable "fixed" voltages (i.e., they remain static during tracing), a
step voltage, and a sweep voltage.  The display monitors current
(vertical) vs. voltage (horizontal), and may be switched to different
suppiies.  Connections to the tube are via a patch panel at the front of
the unit, which uses jumpers to go to an adapter plate.  Two of these
are provided, to allow side-by-side comparison of two tubes, and there
is a switch to select which set of jumpers is active.  While the
switches are marked "plate," "screen," "grid," etc., the patch panels
allow connection of any of the voltages to any of the elements.  This
device is not really a "tester," because it has no built-in settable
criteria or indications for "pass" or fail.  The box can be set up to
provide a dynamic display of any set of curves, including such things as
suppressor and screen grid transconductance.  These were low-volume
products, and the 570 was discontinued in the mid-1960's.  So far as I
know, principal use of them was to match pairs of tubes for various
characteristics.  Prices on the used market have been bid ought of sight
by the golden-ear tube audio crowd, and the last I heard, the going
price was well over $1000.

All of the above devices are DC tests only.  While the Tek 570 provides
a dynamic display, it does so at very low audio frequencies.  The
emissions type tester is clearly a rudimentary "pass fail" device whose
strength is in determining whether the tube will work at all.  The
transconductance tester is somewhat more sophisticated in setting
parameters at an operating point, which may or may not represent the
actual application conditions that the circuit imposes on the tube.

Some of the major issues in selecting a tube tester involve the
configuration of sockets and socket adapters, and availability of test
data for specific tubes.  Also, the condition of the tube sockets has to
be considered.  The useful life of a tube tester was relatively short,
because of socket wear.  While the sockets could have been replaced,
introduction of new tube types and socket configurations continued
steadily into the mid-1960's, and replacement rather than repair of a
worn unit was justified to support newer configurations.  One must keep
in mind that the vast majority of tube testers of both the
emissions and transconductance type were sold and positioned in a
prominent place in a point-of-sale retail business.  They were uncommon
in engineering and manufacturing operations.

What faults can a tube tester find?  Obviously, it will cull out tubes
that are totally non-functional, such as those with open heaters.  Tubes
that light and conduct, but indicate either "?" or the high end of the
"bad" range on a tube tester may function perfectly well in the actual
circuit.  The real problem comes when a tube tester indicates "good" but
the tube won't operate properly in the application circuit.  Hard faults
are fairly easy to find in-circuit.  The only really valid test for tube
condition is in a test under actual operating conditions, and the device
under repair provides those conditions at the application socket.  The
easiest and quickest test at the socket, beyond doing some simple meter
and scope checks, is to plug a known good tube into the socket and see
if that solves the problem.  Even in a shop where sales policy required
100% testing of tubes in a tester, a significant percentage of tube
replacements were for faults found in in-circuit testing involving tubes
that tested "Good" on the tester.

(The following was furnished by Dan Schoo)
Q.  Does anyone have advice for the make and model of the best tube
tester for restoring and maintaining communications receivers
I've seen units made by Hickok (600, 6000, others) as well as
military (TV2C). What are the advantages/disadvantages of each? Thanks.

There are many good testers available. A mutual conductance type is a
better choice than an emission tester. Many times the choice is a matter
of personal preference about the layout and cost. Hickok made many good
instruments. All of them were of similar design and should work equally
well. The 600A, 800, 800A, 6000 and 6000A were very similar. They were
aimed at the radio/TV service industry and were designed to be easily
transported. The 6000 is a nice machine but way overpriced in the current
market. I'd take an 800A any day of the week over a 6000. The 800 and
800A used the meter to measure shorts/leakage instead of a neon lamp in
that capacity. With the meter you could measure leakage to a much lower
level than with the lamp. The only difference between them is the
socketing. The 800A was updated to include Compactrons and Nuvistors but
still retained the old sockets.
The 500 series was a bit larger and not as portable as the 600/800/6000
but similar in function and about equal in performance. The top of the
500 series was the 539C which was closer to a laboratory type tester than
the others. It had three meters and several features you might use in
circuit design. It would test the firing voltage of VR tubes and small
thyratrons. It tested for leakage with the meter but also had a neon
lamp for fast short tests.
The 700 series was larger too and more or less aimed at the industrial
and communications market. These were a little classier than the other
series but not as advanced as the 539. The best machine they made was
the 700. This was closer to a TV-2 than any of the others. It was
designed for laboratory use and had seven meters. If you are just doing
repair and restoration on receivers any of the Hickoks will suffice. The
752A is a good choice because it has some of the desireable features for
communications equipment like VR tube tests, has newer and older type tube
sockets, and reads the leakage on the meter. The TV-2 is a big machine
and for normal service work probably way more than you need.