{"id":14330,"date":"2019-11-03T13:28:20","date_gmt":"2019-11-03T12:28:20","guid":{"rendered":"https:\/\/www.istitutomontani.edu.it\/museovirtuale\/?p=14330"},"modified":"2024-01-10T01:27:20","modified_gmt":"2024-01-10T00:27:20","slug":"oscilloscope-tektronix-type-565-serial-689-tenth-part","status":"publish","type":"post","link":"https:\/\/www.istitutomontani.edu.it\/museovirtuale\/oscilloscope-tektronix-type-565-serial-689-tenth-part\/","title":{"rendered":"Oscilloscope Tektronix Type 565 serial 689, eighth part (MITI Museum)"},"content":{"rendered":"

Oscilloscopio Tektronix Type 565. Ottava parte. <\/span>
\nNell\u2019inventario D del 1956 si trova al n\u00b0 3747 e risulta acquistato nell\u2019agosto del 1964; vi si legge: \u201cSilvestar ltd. Milano. Oscilloscopio Tektronix mod. 565 matr 689. Dest. Elettronica \u20a4 1^{\u0387<\/sup>678^{\u0387<\/sup>600\u201d. Insieme alla fotocamera che \u00e8 al n\u00b0 3746, dove si legge: \u201cSilvestar ltd. Milano. Macchina fotografica Tektronix mod. C-12 completa di Bezel-Tektronix. Dest. Elettronica. \u20a4 557^{\u0387<\/sup>700\u201d.<\/span>
\nIl testo continua dalla settima parte.
\n<\/span>\u00a7\u00a7\u00a7<\/span><\/p>\n}}}

\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00abLOW VOLTAGE POWER SUPPLIES
\n<\/strong>General
\n<\/strong>The Low Voltage Power Supplies consist of four<\/span>
\ninterdependent, regulated voltage sources. Each supply is<\/span>
\ncapable of maintaining an accurate dc output voltage<\/span>
\n having a low percentage of ripple, even though the<\/span>
\n input line voltage and the output load may vary considerably.<\/span>
\n-100 Volt Supply<\/span>
\n $\"\"$
\n<\/strong>When the design-center voltage is applied to the primary<\/span>
\nof T601, the voltage across secondary terminals 6 and 11 is
\n<\/span>about 145 volts rms. This voltage is applied to a conventional <\/span>full-wave bridge rectifier, D612, producing about 200 <\/span>volts dc across filter capacitor C611. This voltage is then <\/span>divided between the load and the series regulator tubes.
\n<\/span>The block diagram Fig. 3-14 shows the basic elements of the <\/span>circuit which accomplish this division.
\n<\/span><\/span>The regulator tubes function as a variable resistor in<\/span>
\nseries with the load. In order to maintain a stable voltage
\n<\/span>across the load, their plate resistance must be changed as
\n<\/span>required to offset the effect of a change in line voltage or<\/span>
\nload current. To accomplish this, the output voltage is<\/span>
\nconstantly compared to a fixed reference voltage by the
\n<\/span>comparator V636. Any error thus detected is amplified and
\n<\/span>applied to the series regulators. Their plate resistance is
\n<\/span>thereby changed and the proper output voltage is restored.<\/span>
\nRefer to the Power Supply schematic in the back of this<\/span>
\nmanual. The voltage reference tube V639 applies a stable
\n<\/span>-85 volts to the \u2018A\u2019 grid of a long-tailed difference amplifier<\/span>
\nV636. This establishes an essentially constant voltage at the<\/span>
\ncommon cathodes of both V636A and V636B. A sample of<\/span>
\nthe supply output voltage is obtained from the -100 VOLTS
\n<\/span>control, R624. (This sample will always be about -85 volts,
\n<\/span>since it is the voltage actually being regulated to match the<\/span>
\nreference voltage. Since the -100 VOLTS control is set so<\/span>
\nthe sample is 85% of the total voltage across R623, R624 and <\/span>R625, the total voltage will also be regulated.) If a positive-<\/span>going change occurs in the output voltage, the grid voltage <\/span>on V636B changes in the positive direction. The current <\/span>through V636B increases and its plate voltage drops. This <\/span>negative-going voltage change is applied to the control <\/span>grid of amplifier V614. The current through V614 decreases <\/span>and its plate voltage rises, carrying the grids of V617 and <\/span>V627 positive. The regulator tubes\u2019 plate resistance <\/span>decreases, therefore increasing the current through the load.<\/span>
\nThis results in an increased voltage drop across the load, thus <\/span>offsetting the error.<\/span>
\nNegative-going changes are corrected in the same way<\/span>
\nexcept for error signal polarities. Due to the high gain of the<\/span>
\namplifier circuits and their ability to respond quickly, the<\/span>
\nsupply in effect corrects for changing line voltage and load<\/span>
\nconditions before a significant change can occur in the<\/span>
\noutput voltage.<\/span>
\nThe dc voltage across C611 bears a substantial amount<\/span>
\nof ripple. A sample of this ripple is applied to the screen<\/span>
\ngrid of V614. The screen grid acts as a second signal grid<\/span>
\nand aids in eliminating much of the ripple from the supply
\n<\/span>output. C636 and C629 also aid in eliminating ripple since<\/span>
\nthey offer less attenuation to ac error signals than do the<\/span>
\nresistive voltage dividers. C626 lowers the supply output<\/span>
\nimpedance.<\/span>
\nR626 and R627 are particularly important elements in<\/span>
\nthe -100 volt supply. It would be impractical to pass all
\n<\/span>of the current required by the load through the series<\/span>
\nregulator tubes.\u00a0 Since line voltage and load current variation<\/span>limits are known, the series regulator tubes<\/span>
\nneed only carry enough current to allow for these variations. Hence, R626 <\/span>carries a substantial amount of the current required by the <\/span>circuits within the Type 565. R627 serves the same purpose for each of the vertical plug-in units. Depending on the amount of current required by each type of plug-in unit, the connections within the plug-in will be one of the following:<\/span>
\n1.No connection to pin 22 of the plug-in unit <\/span>
\n interconnecting plug (low current demand).<\/span>
\n2.A resistor connected between pins 22 and 9 (moderate<\/span>
\ncurrent demand).<\/span>
\n3.A wire connected between pins 22 and 9 (maximum<\/span>
\ncurrent demand).
\n<\/span>+125 Volt Supply
\n<\/strong>The operation of the +125 volt supply is similar, in most
\n<\/span>respects, to that of the -100 volt supply.
\n<\/span>The -100 volt supply serves as the voltage reference for
\n<\/span>the +125 volt supply. R673 and R674 are the principle
\n<\/span>circuit elements that determine the accuracy of the output
\n<\/span>voltage.
\n<\/span>Full-wove rectification of the ac supply voltage is provided
\n<\/span>by rectifiers D662A and D662B. These two diodes are
\n<\/span>shared with the +300 volts supply to form half of a full-
\n<\/span>wave bridge.
\n<\/span>+300 Volt Supply
\n<\/strong>The only significant difference between the +125 and
\n<\/span>+300 volt supplies is the +420 volt unregulated output<\/span>
\nassociated with the +300 volt supply. This voltage is used<\/span>
\nin the oscillator portion of the Crt Circuit.<\/span>
\n-12.2 Volt Supply
\n<\/strong>R643 and R644 provide the reference voltage at the base<\/span>
\nof Q644. Any voltage error at the emitter of Q644 is<\/span>
\namplified, but not inverted, and applied to the base of Q654.<\/span>
\nQ654 amplifies and inverts the error signal, providing the<\/span>
\nnecessary drive for the series regulator Q657. C647 and<\/span>
\nR647 provide phase correction for Q654, thereby stabilizing<\/span>
\nthe regulator.<\/span>
\nThe -12.2 volt supply does not employ shunt resistors<\/span>
\nas do the other three supplies. Instead, all load current<\/span>
\npasses through the series regulator. Fuse F640 protects<\/span>
\nQ657 from overload. C657 reduces the supply output<\/span>
\nimpedance.<\/span>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0<\/span>
\nCRT CIRCUIT<\/span>
\n<\/strong>\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 CAUTION
\n<\/strong>Always make or break voltmeter connections at<\/span>
\nany of the high-voltage points in the Crt Circuit<\/span>
\n(except for the HIGH VOLTAGE TEST POINT)<\/span>
\nwhile the instrument is turned off. If a connection<\/span>
\nis made or broken while the power is on, a small<\/span>
\narc may occur which will produce voltage and<\/span>
\ncurrent transients within the circuit. Such transients<\/span>
\ncan destroy one or more of the semiconductor<\/span>
\ndevices in the Crt Circuit.<\/span>
\nHigh Voltage Power Supply
\n<\/strong>The cathode-ray tube (crt) in the Type 565 Oscilloscope<\/span>
\nrequires an accelerating potential of about 4100 volts.<\/span>
\nApproximately 200 volts of this is supplied by the low-voltage <\/span>power supply. The remaining 3900 volts comes from the <\/span>high-voltage power supply.<\/span>
\n $\"\"$
\nThe high-voltage power supply consists of an oscillator,<\/span>
\na step-up transformer, rectifiers, and circuits which regulate<\/span>
\nthe high voltage (see Fig. 3-15). Transformer T801 steps up<\/span>
\nthe oscillator signal to the required amplitude, and V822
\n<\/span>rectifies the signal, producing high voltage dc. This voltage
\n<\/span>is applied to the crt from several points in a high resistance<\/span>
\nvoltage divider which includes the INTENSITY and FOCUS <\/span>controls.<\/span>
\nRefer to the Crt Circuit schematic in the back of this<\/span>
\nmanual. The oscillator is a modified Hartley which operates<\/span>
\nat a frequency determined by the primary winding inductance <\/span>and inter-turn capacitance of transformer T801. Oscillator <\/span>frequency is not critical and is usually between 30 kc <\/span>and 50 kc. The voltage on the screen grid of V800<\/span>
\ndetermines the amplitude of the oscillator signal, which in turn <\/span>determines the value of dc high voltage produced. This
\n<\/span>property of the circuit is used to establish and maintain the
\n<\/span>correct high voltage; -3900 volts.
\n<\/span>The high voltage is applied to a high resistance voltage
\n<\/span>divider which includes the INTENSITY, FOCUS, and HIGH <\/span>VOLTAGE controls. With any particular setting of the <\/span>HIGH VOLTAGE control, a certain percentage of the total <\/span>voltage across the voltage divider is applied to the grid
\n<\/span>of V814B. This grid voltage will always be about -103.5
\n<\/span>volts, since it is the voltage actually being regulated. Since
\n<\/span>the grid voltage is regulated and is a known fraction of the
\n<\/span>high voltage, the high voltage will also be regulated.
\n<\/span>When the voltage at the grid of V814B is -103.5 volts,
\n<\/span>the voltage at the plate of V814B and the grid of V814A
\n<\/span>will be about -2 volts. The voltage at the plate of V814A
\n<\/span>and at the screen of V800 will be about +90 volts. If the
\n<\/span>high voltage should change, the voltage at the grid of
\n<\/span>V814B will also change. This change will be amplified by
\n<\/span>V814B and V814A, thus changing the voltage on the screen
\n<\/span>of V800. If, for example, the screen voltage is made more
\n<\/span>positive, the oscillator signal amplitude will increase and
\n<\/span>a greater dc high voltage will be produced.
\n<\/span>Due to C862, the high gain of the error amplifier, and
\n<\/span>the ability of the circuit to respond quickly, there is rarely
\n<\/span>any significant variation in the high voltage. This is
\n<\/span>because the correction for any change begins at nearly the
\n<\/span>same instant as the change. Thus, a change is stopped
\n<\/span>and corrected before it can become more significant.
\n<\/span>Intensifying Circuit
\n<\/strong><\/span>The intensifying Circuit operates only when the TRIGGERABLE <\/span>AFTER DELAY INTERVAL and STARTS AFTER DELAY <\/span>INTERVAL modes of Time Base \u2018B\u2019 are used. Its only function <\/span>is to dc couple a positive-going pulse to the upper <\/span>beam CRT control grid. The normal voltage on this grid <\/span>is about -3975 volts. The positive-going pulse at the <\/span>control grid will cause a brightened segment within the upper <\/span>beam trace.
\n(For more information about the purpose of <\/span>the brightened trace segment, see \u201cUsing the \u2018B\u2019 MODE <\/span>Switch\u201d in Section 2 of this manual.)
\n $\"\"$
\n<\/span>The basic elements of the intensifying Circuit are shown
\n<\/span>in Fig. 3-16. Pulse Shaper V834 converts the applied
\n<\/span>unblanking pulse into alternate positive and negative voltage <\/span>pulses. These pulses actuate the bistable tunnel-diode <\/span>switch D845 to produce a negative-going \u00a0turn-on pulse for <\/span>Current Switch Q843.
\n<\/span>When the Current Switch Q843 is open, the floating 11volt
\n<\/span>supply does not produce a voltage drop across R849.
\n<\/span>The voltage on the upper beam crt control grid during
\n<\/span>this time depends entirely upon the setting of the INTENSITY <\/span>control. \u00a0However, when the Current Switch is closed, <\/span>current through R849 produces a voltage drop that drives the <\/span>crt grid more positive. This causes a portion of the upper <\/span>beam trace to be brightened.
\n<\/span>For the following portion of the circuit description, refer
\n<\/span>to the Crt Circuit schematic in the back of this manual.
\n<\/span>The LOWER HORIZ. DISPLAY switch provides a choice
\n<\/span>between three signal sources for unblanking \u00a0the crt: \u2018A\u2019
\n<\/span>Unblanking, \u2018B\u2019 Unblanking, or +125 volts dc. Each of
\n<\/span>these signals can cause the intensifying \u00a0Circuit to operate.
\n<\/span>However, only the \u2018B\u2019 Unblanking signal will cause the
\n<\/span>Intensifying\u00a0 Circuit to produce an intensified crt display.
\n<\/span>Hence, the following description assumes the use of the
\n<\/span>\u2018B\u2019 Unblanking signal.
\n<\/span>If Time Base \u2018B\u2019 is not generating a sweep, the CRT
\n<\/span>unblanking voltage from the LOWER HORIZ. DISPLAY switch <\/span>is about\u00a0 +25 volts and V834 is cutoff. When Time Base \u2018<\/span>B\u2019 is then triggered, the unblanking voltage switches sharply <\/span>to about +125 volts and V834 conducts heavily. (It is <\/span>important\u00a0 to note that the circuit operates only with the \u2018B\u2019 <\/span>MODE switch in the STARTS AFTER DELAY INTERVAL or <\/span>TRIGGERABLE AFTER DELAY INTERVAL position to provide <\/span>cathode current for V834.) The sudden surge of current <\/span>through T841 produces a sharp pulse in the secondary <\/span>circuit.
\n $\"\"$
\n<\/span>The dynamic characteristics of tunnel diode D845 are
\n<\/span>shown in Fig. 3-17. Prior to the arrival of the pulse, the
\n<\/span>tunnel diode maintains stable forward conduction at point
\n<\/span>A on the curve. The voltage across the diode is then about
\n<\/span>40 millivolts. This voltage is applied to the base-emitter
\n<\/span>junction of Q843, but is not sufficient to cause the transistor
\n<\/span>to conduct. Since there is no current through Q843, there
\n<\/span>is no voltage drop across R849 and the voltage on the
\n<\/span>upper beam crt control grid depends only on the setting
\n<\/span>of the INTENSITY control (usually about -3975 volts at
\n<\/span>normal trace brightness).
\n<\/span>When the pulse is produced in the secondary circuit of
\n<\/span>T841, the diode is driven through point B on the curve. The
\n<\/span>diode is unstable at point B and therefore switches rapidly
\n<\/span>to point C. As the input pulse subsides, the diode is unable
\n<\/span>to continue operation at point C because R846 cannot satisfy <\/span>the diode’s simultaneous demands for heavy current and <\/span>high state voltage. Current then diminishes and the diode <\/span>assumes stable operation at point D.
\n<\/span>With the voltage across the diode now about 400
\n<\/span>millivolts, Q843 is turned on. The current path is from the
\n<\/span>positive end of C828, through Q843, R349, to the CONTRAST <\/span>control (R848), and to the negative end of C828. The <\/span>voltage drop thus produced across R849 drives the upper beam <\/span>crt control grid several volts in the positive direction. This <\/span>causes an increase in crt beam current and the trace <\/span>becomes brighter.
\n<\/span>When the unblanking\u00a0 pulse ends, V834 is suddenly cutoff,
\n<\/span>producing a pulse in the secondary circuit with polarity
\n<\/span>opposite that of the previous pulse. The tunnel diode is
\n<\/span>driven from operating point D (Fig. 3-17) through point E.
\n<\/span>The diode is unstable at point E, and therefore switches
\n<\/span>rapidly to point\u00a0 F. At this point, R846 cannot satisfy the
\n<\/span>diode’s demand for both low current and low state voltage.
\n<\/span>Therefore, the current increases and the tunnel diode resumes <\/span>stable operation at point A. The transistor reverts to cutoff, <\/span>the upper beam crt control grid voltage drops to its
\n<\/span>previous, more negative value, and the trace dims.
\n<\/span>The CONTRAST control provides a means of controlling
\n<\/span>the amplitude of the intensifying pulse and therefore the
\n<\/span>amount of brightness increases during the brightened
\n<\/span>segment of the upper beam trace. This is accomplished in the <\/span>following manner.
\n<\/span>As is true with most switches, transistor Q843 has a very
\n<\/span>high series resistance when turned off and a very low series
\n<\/span>resistance when turned on. Therefore, nearly all of the
\n<\/span>11-volt supply voltage is dropped across R849 when Q843
\n<\/span>is turned off. Hence, by controlling the total voltage
\n<\/span>across the transistor and resistor, it is possible to control
\n<\/span>the output pulse amplitude.
\n<\/span>The CONTRAST control R848 and R847 form a voltage
\n<\/span>divider across the 11-volt supply. By turning the CONTRAST <\/span>control, the operator can vary the voltage across Q843 <\/span>and R849 between about 2 and 11 volts.
\n<\/span>Unblanking
\n<\/strong><\/span>A trace or spot can be obtained on the crt at all times
\n<\/span>when an external signal is used for horizontal deflection.
\n<\/span>However, such is not the case when horizontal deflection
\n<\/span>is provided by one of the time base generators. When the
\n<\/span>oscilloscope is used in the latter manner, a blanking signal
\n<\/span>from the time base generator is applied to the crt. This
\n<\/span>signal turns off the beam during sweep retrace and holds
\n<\/span>it off until the next sweep begins.
\n<\/span>Each of the two crt electron guns has a deflection plate
\n<\/span>blanking system. A pair of deflection plates, similar to
\n<\/span>those used for vertical and horizontal deflection, is placed
\n<\/span>between the control and focus grids in each gun. One
\n<\/span>plate in each pair is permanently connected to the +125
\n<\/span>volt supply. The second plate can be connected to the
\n<\/span>+125 volt supply or to one of the time base generators,
\n<\/span>depending on the setting of the horizontal display switches.
\n<\/span>The beam is constantly unblanked when the +125 volt
\n<\/span>(EXT.) switch position is used.
\n<\/span>If one of the time base generators provides horizontal
\n<\/span>deflection for a particular beam, that beam will be
\n<\/span>alternately blanked and unblanked in the following manner:
\n<\/span>Between sweeps, the voltage applied to the crt blanking
\n<\/span>plate by the time base generator will be about +25 to +30
\n<\/span>volts With the other plate at +125 volts, the beam is
\n<\/span>drawn into and absorbed by the more positive plate. Little
\n<\/span>or no beam current gets past this point. When the time
\n<\/span>base generator begins a sweep, it quickly increases the
\n<\/span>voltage on the blanking plate to about +125 volts. Since
\n<\/span>the blanking plate potentials are then essentially equal, the
\n<\/span>beam current is released and passes on toward the face of
\n<\/span>the crt to produce light.
\n<\/span>Multi-trace Chopped Blanking
\n<\/strong><\/span>The Type 565 Oscilloscope can be used with multi-trace
\n<\/span>plug-in units such as the Type 3A74. When this type of
\n<\/span>plug-in unit is operated in the \u201cchopped\u201d mode, the
\n<\/span>display may consist of up to four traces per beam. The plug-in <\/span>forms the display by switching on each information-
\n<\/span>channel, one at a time, in a rapidly repeating sequence.
\n<\/span>The vertical signal information available at the output
\n<\/span>of the plug-in during the very short time required to switch
\n<\/span>channels, is of no value in the display. Hence, this information <\/span>is blanked out.
\n<\/span>A pulse from the plug-in unit is available at pin 24 of
\n<\/span>the plug-in interconnecting jack when switching from one
\n<\/span>channel to the next. This pulse is coupled through a dc
\n<\/span>blocking capacitor to the appropriate crt cathode. The
\n<\/span>pulse momentarily drives the cathode positive and cuts off
\n<\/span>the beam current until the plug-in has finished switching
\n<\/span>to the next channel.
\n<\/span>Diodes D892 and D882 are dc restorers. They insure
\n<\/span>equal trace brightness for the chopped and conventional
\n<\/span>mode. They permit the crt cathodes to be driven positive
\n<\/span>by the incoming signal, but prevent the cathodes from being
\n<\/span>driven more negative than the voltage at the HIGH VOLTAGE <\/span>TEST POINT; -3900 volts.
\n<\/span>Intergun Shield and Isolation Shield
\n<\/strong><\/span>Proper adjustment of the INTERGUN SHIELD and ISOLATION <\/span>SHIELD controls insures that (1) a straight line display <\/span>will appear as a straight line, regardless of its position <\/span>on the screen, and that (2) a display which is well focused <\/span>at the center of the screen will also exhibit good focus at <\/span>the edge of the screen. These controls also affect the <\/span>deflection sensitivity and scan limits of the crt.
\n<\/span>Trace Alignment
\n<\/strong><\/span>The trace alignment coil surrounds the crt at a point
\n<\/span>about 6 inches behind the face plate. The plane of the
\n<\/span>coil is parallel to the plane of the face plate. The TRACE
\n<\/span>ALIGNMENT control determines the amount and direction
\n<\/span>of the dc current through the coil. By adjusting this control,
\n<\/span>the entire display can be rotated a few degrees clockwise
\n<\/span>or counterclockwise about the axis of the crt.
\n<\/span>Display alignment is affected by the earth’s magnetic
\n<\/span>field and may change when the instrument is moved. In
\n<\/span>such cases, the operator can quickly realign the display
\n<\/span>with the graticule markings by adjusting the TRACE
\n<\/span>ALIGNMENT control.
\n<\/span>AMPLITUDE CALIBRATOR
\n<\/strong><\/span>The Amplitude Calibrator generates square waves of an
\n<\/span>accurate peak-to-peak voltage available in six steps at the
\n<\/span>CAL. OUT connector. The square wave output is positive-
\n<\/span>going from ground. The frequency is about one kc, rise and
\n<\/span>fall times are several microseconds, and the duty factor is
\n<\/span>about\u00a0 0.5. Because of its intended use, only the peak-to-
\n<\/span>peak voltage accuracy of the Amplitude Calibrator is given
\n<\/span>a specific tolerance.
\n $\"\"$
\n<\/span>Refer to the block diagram, Fig. 3-18. The Amplitude
\n<\/span>Calibrator consists of an astable multivibrator, an output
\n<\/span>cathode follower, and a precision output divider. The
\n<\/span>multivibrator switches the cathode follower alternately between <\/span>cutoff and conduction. The cathode follower output voltag<\/span>is an accurate +100 volts during conduction and zero volts <\/span>during cutoff. The output divider provides five lower <\/span>amplitudes from the basic 100 volt square wave. The CAL. OUT <\/span>voltage is selected by setting the PEAK-TO-PEAK VOLTS <\/span>switch to the desired value.
\n<\/span>Refer to the Amplitude Calibrator schematic diagram in
\n<\/span>the back of the manual.
\n<\/span>V915A and V905 form a conventional astable plate
\n<\/span>coupled multivibrator.\u00a0 In the multivibrator action, V905
\n<\/span>operates as a triode with the screen grid acting as the
\n<\/span>plate. When V905 conducts, a portion of the cathode
\n<\/span>current goes to the pentode plate and drops the plate voltage
\n<\/span>to about\u00a0 -20 volts. This voltage is applied to the grid of
\n<\/span>V915B. V915B is cutoff and its cathode voltage is zero.
\n<\/span>When V905 is cut off, the voltage at its plate is
\n<\/span>determined by the voltage divider; R909, R910, and R911. The <\/span>CAL. AMPL. control, R910, is set during calibration so the <\/span>voltage at the cathode of V915B will be exactly +100
\n<\/span>volts when V905 is cut off.
\n<\/span>A 0.25 ohm resistor located between the CAL. OUT coax
\n<\/span>connector and ground is approximately equal to the
\n<\/span>resistance of the braid of a 42 inch long RG-58A\/U coax
\n<\/span>cable. Its purpose is to cancel any coax braid ground
\n<\/span>current effects on calibrator voltage accuracy that may exist
\n<\/span>when the Type 565 AMPLITUDE CALIBRATOR is used as a <\/span>signal source between the oscilloscope and some other
\n<\/span>instrument chassis. The ground currents in this case are
\n<\/span>usually developed in the ac power line third-wire grounding
\n<\/span>system when the Type 565 and the other instrument
\n<\/span>chasses are supplied from different convenience outlets\u00bb.
\n<\/span>\u00a7\u00a7\u00a7
\n<\/span>Abbiamo omesso la pur interessante sezione MAINTENANCE del manuale delle istruzioni.
\n<\/span>Per consultare le altre schede dedicate a questo oscilloscopio esposto al museo MITI (su proposta di Fabio Panfili)<\/span> scrivere \u201c565\u201d su Cerca.
\n<\/span>Elaborazioni di Fabio Panfili.
\nPer ingrandire le immagini cliccare su di esse col tasto destro del mouse e scegliere tra le opzioni.<\/span><\/span> $\"\"$ $\"\"$ $\"\"$ $\"\"$ <\/p>\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

Oscilloscopio Tektronix Type 565. Ottava parte. Nell\u2019inventario D del 1956 si trova al n\u00b0 3747 e risulta acquistato nell\u2019agosto del 1964; vi si legge: \u201cSilvestar ltd. Milano. Oscilloscopio Tektronix mod. 565 matr 689. Dest. Elettronica \u20a4 1\u0387678\u0387600\u201d. Insieme alla fotocamera che \u00e8 al n\u00b0 3746, dove si legge: \u201cSilvestar ltd. Milano. Macchina fotografica Tektronix mod. … <\/p>\n