Introduction (this page -- see below)
- Crystal demodulator
and advantages. Series and shunt detectors. Characteristics and requirements.
Probe filter. Input voltage to probe. Probe input capacitance. Probe circuit
time constants. Scope preamplifier. Grounding the probe. Interchangeability
- Working with crystal probes: Signal
tracing. Waveforms. Undershoot. I.f. gain and alignment. Single stage
response. Buzz. Testing video amplifiers. Crystal diode voltage and current
ratings. Adjusting a video amplifier. Ratio-detector curve. Calibrating
a marker generator. Sweep generator output. Grounds. Waveform errors.
Maximum signal voltage.
- Voltage-doubler probes: Advantages.
Voltage limitations. Peak-to-peak probe. Calibration of marker generator.
Making ratio-detector S-curve. I.f. signal and sync buzz tracing. Color
TV testing. Dead-stage indication, regeneration, sync buzz. Peak-to-peak
voltage measurements. Frequency response. 60-cycle rejection.
- Balanced probes: Impedance
matching. Need for balanced probe. Transmission line impedance. Zero-volt
reference line. Testing transmission lines. Mis match between transmission
line and antenna or TV input. Trans mission line losses. Construction
of balanced probe. Gain and response of TV boosters. Balun.
- Low-capacitance probes: Circuit
loading. Probe attenuation and design. Use of probe in high impedance,
high-voltage circuits and in circuits with high d.c. component. Probe
response vs. scope response. Scope calibration. Adjusting and extending
voltage range. Tracing the TV sync signal. High-voltage adapter. Building
a low-capacitance probe.
- High-voltage probes: Probe
design and construction. How the probe works. Attenuation factor. Miscellaneous
cables. Use with uncompensated scope. Behavior in 60-cycle circuits.
100-to-1 probe. Spotting flyback defects. Ripple in high-voltage supply.
High-voltage buzz. Multiplication factor. Probe resistance. Safety precautions.
- Isolation and direct probes: Isolation
probe for v.t.v.m. Reasons for using isolation probe. Probe construction.
Effect of probe on meter calibration. Using the probe with a multitester.
Using the isolation probe. Isolation probe for scope. Marker indication.
The direct probe. Combined direct and isolation probe. Test leads.
- Specialized probes: Audio tracer. Capacitor-tester.
Hum probe. Frequency-compensated probe. Probe amplifier. A.f. and r.f.
tracer. Miniature test probes. R.f. indicator. R.f. voltmeter probe.
Quadrupler probe. Magic-eye probe. Plugs and connectors. Neon-bulb probe.
Probe housing. Cathode follower probe. Transistor probe.
- The Chromatic probe: Probe circuit. Development of
a wide-band sweep. Single-image response. Using the Chromatic Probe.
D.C. voltage at video amplifier input. Testing color TV. Demodulator
probe limitations. Chromatic Probe maintenance. Chromatic Amplifier.
- Vacuum-tube probes: Transit time. Contact potential.
High-frequency probe. Peak-to-peak probe. Cathode-follower probe. Using
the cathode-follower probe. Grid-leak detector probe. Grid-dip probe.
The grid-dip probe at work. Probe housing. Portable signal tracer. Signal
tracer for AM, FM, and TV. Tube probe.
- Supplement--Television waveforms: Examining TV waveforms.
Input to grid of horizontal amplifier. Pulses at plate of a.g.c. amplifier.
Video i.f. waveforms. Output of V.H.F. tuner. Wave at input to horizontal
deflection coil. Video amplifier waveshapes. TV wave in sync circuits.
Wave at plate of vertical multivibrator.
A probe is a link. It is a device connected between a test instrument
(usually a scope or v.t.v.m.) and a radio or TV set being repaired. The
simplest type of probe can be nothing more than just a pair of test leads.
Alternatively, it can be complicated to the extent that a complete detecting
and amplifying system will be inside the probe housing. Although most probes
are characterized by the use of few components and elementary circuit structure,
yet the work they must perform is out of all proportion to their size.
Because a piece of test equipment, such as a probe, is small or inexpensive,
does not mean that it is unimportant or unnecessary. The finest v.t.v.m.
or scope is limited by the kind of probe you use with such equipment and
by your own knowledge of probes.
Regardless of the particular probe you use at any time, a probe has one
job and one job only. A probe is supposed to bring the voltage or waveshape
being measured or examined out of the receiver and into the test instrument.
In effect, what you are doing is getting the voltage or waveshape that
interests you out of the defective receiver and into the open where it
can be more easily inspected.
There are a few requirements that are imposed on the probe.
It must not load the circuit being checked. It should not reduce the voltage
at the point under test. A probe can be used to measure a voltage, in which
case the voltage must remain the same at the point being tested, with or
without the probe connection.
If a probe is used for waveshape analysis, it must pick up that waveshape
and transfer it to your scope without making any change in the shape of
that wave. And finally, since probes are used for making dynamic tests
(that is, with the radio or TV set turned on and working) the probe must
do nothing to disturb the set.
The number of probes you will need for your servicing work will depend
entirely upon you. Obviously, the ideal arrangement is to have a probe
for each specific function. Although probes are comparatively inexpensive
you can build your own if you wish, buy individual probes as you need them
or else get a complete probe set. Again this is a matter for personal choice.
More than almost any kind of project, a technical book is a cooperative
enterprise. Many persons and organizations were kind enough and gracious
enough to make this publication a possibility. We acknowledge with thanks,
assistance from these well-known companies: Admiral Corp.; Allen B. Du
Mont Laboratories, Inc.; Browning Laboratories; Cornell-Dubilier Electric
Corp.; Electronic Instrument Co., Inc.; Electronic Measurements Corp.;
General Electric Co., Hickok Electrical Instrument Co., Jackson Electrical
Instrument Co.; Linear Equipment Laboratories, Inc.; Magnavox Co.; National
Bureau of Standards; Precise Development Corp.; Precision Apparatus Company,
Inc.; Pres Probe Co.; Radio Corp. of America; RADIO-ELECTRONICS Magazine,
Scala Radio Co.; Simpson Electric Co.; Supreme, Inc.; Sylvania Electric
Products, Inc.; Tektronix, Inc.
(Note: This guide based on the 1955 book)
Also see: Industrial Electronics (in the