A and B Triggering both where applicable

COUPLING Determines the method used to couple signal to input of trigger circuits. AC Rejects DC and attenuates signals below about 60 Hz. Accepts signals above about 60 Hz. signals below about 50 kHz. Ac- LEVEL cepts signals above about 50 kHz. HF REJ Accepts signals between 60 Hz and 50 kHz. Rejects DC and attenuates all signals outside the above range. DC Accepts all trigger signals from DC to 100 MHz or greater. NORM Internal trigger signal obtained from Vertical Deflection System. Actual...

Vertical Deflection System Channel 1 Channel

This instrument may be damaged if operated with the line voltage selector switch or the Regulating Range Selector assembly set to incorrect positions for the line voltage applied. The 465 is designed to be used with a three-wire AC power system. If a three-to two-wire adapter is used to connect this instrument to a two-wire AC power system, be sure to connect the ground lead of the adapter to earth (ground). Failure to complete the ground system may allow the chassis of this instrument to be...

Operating Voltage

This instrument is designed for operation from a power source with its neutral at or near earth (ground) potential with a separate safety-earth conductor. It is not intended for operation from two phases of a multi-phase system, or across the legs of a single-phase three-wire system. Color-coding of the cord conductors is as follows (in accordance with National Electrical Code) Safety earth (ground) Green (or green with yellow tracer) 3. To change regulating ranges, loosen the two captive...

Table Of Contents cont

SECTION 3 CIRCUIT DESCRIPTION (cont) Page Low-Voltage Power Supply Secondary Circuit 3-20 Fan Motor Circuit Cabinet Removal 4-1 Preventive Maintenance Recalibration 4-2 Corrective Maintenance Obtaining Replacement Parts 4-2 Test Equipment Required 5-1 Performance Check Horizontal System Check 5-13 Short-Form Calibration Power Supplies And Display 5-16 Horizontal System 5-21 Detailed Calibration Calibrator, Gates, & Ext Z-Axis 5-60 SECTION 7 DIAGRAMS & CIRCUIT BOARD ILLUSTRATIONS SECTION 8...

Cleaning

Tektronix 465 Crt Cleaning

The 465 should be cleaned as often as operating conditions require. Accumulation of dirt in the instrument can cause overheating and component breakdown. Dirt on components acts as an insulating blanket and prevents efficient heat dissipation. It also provides an electrical conduction path which can result in instrument failure. The cabinet provides protection against dust in the interior of the instrument. Operation without the cabinet in place necessitates more frequent cleaning. The...

ZAxis Amplifier

The Z-Axis Amplifier circuit controls the CRT intensity level from several inputs. The effect of these input signals is to either increase or decrease the trace intensity, or to completely blank portions of the display. The input transistor Q1466 is a current-driven, low input impedance amplifier. It provides termination for the input signals as well as isolation between the input signals and the following stages. The current signals from the various control sources are connected to the emitter...

High Voltage Oscillator

Q1418 and associated circuitry compose the high-voltage oscillator that produces the drive for high-voltage transformer T1420. When the instrument is turned on, current through Q1416 provides forward bias for Q1418. Q1418 conducts and the collector current increases, which develops a voltage across the collector winding of T1420. This produces a corresponding voltage increase in the feedback winding of T1420, which is connected to the base of Q1418, and Q1418 conducts even harder. Eventually...

Gain Setting Amplifier

Q1226 and Q1236 are an emitter coupled push-pull amplifier stage. Q1244 is a constant current supply for the stage. The gain of the Horizontal Amplifier is controlled by adjusting the resistance connected between the emitters of this stage. The X1 Gain adjustment R1237 adjusts unmag-nified horizontal gain and the X10 Gain adjustment R1238 adjusts magnified horizontal gain. Magnifier Registration adjustment R1225 balances quiescent DC current in Q1226 and Q1236 so that a center screen display...

Input Paraphase Amplifier

Q1224 and Q1234 compose the Input Paraphase Amplifier. This is an emitter-coupled amplifier stage that converts the single-ended input signal to a push-pull output signal. The signal at the collector of Q1224 is opposite in phase to the input signal. The signal at the collector of Q1234 is in phase with the input signal. Thermistor resistor RT1230 reduces in value with increases in ambient temperature to increase the gain of the stage. This compensates for changes in amplifier gain that occur...

A Gate And B Gate Emitter Followers

Q1314 and Q1334 are emitter followers providing the +A GATE and +B GATE output signals available at the instrument rear panel. The output signals are positive-going rectangular waveforms, approximately 5.5 volts in amplitude. The amplitude is set in the collectors of 01304 and Q1324. For example, when 01304 is conducting the base of 01314 can go no more negative than approximately -0.7 volt (limited by CR1304), When Q1304 is not conducting, the base of Q1314 rises to the decoupled +5 volts...

Sweep ZAxis Gate

Q1304 and Q1306 comprise the A Sweep Z-Axis Gate. They form an emitter-coupled stage where only one transistor can be conducting at any time. The controlling signal inputs come from the collector of Q862 in the A Sweep Gate, the blanking signal from Q1014 in the A Sweep Generator, and Q824 in the B Latch Multivibrator (only in the MIX mode of operation). The blanking signal for use in the Z-Axis Amplifier is taken from the collector of Q1306 (through CR1342). The collector signal of Q1304 is...

Sweep Holdoff Amplifier

Q854 is the A Sweep Holdoff Amplifier. The holdoff gate waveform is applied to the base of Q854 through R858 and C858 from pin 17 of U870. When Q854 is turned off (during holdoff time), its collector is LO and CR851 is forward biased, which resets both the Arm and Fire trigger TD's in the A Trigger Generator. When Q854 is turned on (any time other than holdoff time), its collector level is HI and CR851 is reversed biased. This allows the trigger TD's in the A Trigger Generator to respond to the...

Sweep Control Integrated Circuit

U870 is the Sweep Control Integrated Circuit. Several functions are performed in this stage, depending on the mode of operation of the instrument sweep generators. The following is a brief explanation of the function associated with each pin of the IC. Pin 1. This is the positive Auto Sense input. The signal connected here comes from the A Fire Trigger TD. Pin 2. This is the negative Auto Sense input. A fixed DC level established by R871 and R872 is connected here. Pin 3. This is the + auto...

Sweep Start Amplifier

Just before the sweep starts to run down, the levels at the bases of Q1002 A and B are approximately equal. When the sweep starts to run down, the base of Q1002B goes negative, which increases the forward bias on CR1004. This in turn decreases the forward bias on CR1001, which, very shortly after the start of the sweep, becomes reverse biased to interrupt the current through Q1002A. The circuit remains in this condition until after the sweep retrace is complete. When the circuit returns to...

Sweep Generator Differences

There are three prime differences between the A and B Sweep Generators. The B Sweep Output Buffer Amplifier is prevented from passing the B Sweep signal to the Horizontal Amplifier in the A and A INTEN positions of the HORIZ DISPLAY switch. There is a transistor stage connected as a constant current source in the emitter circuit of Q1062A and B (corrects for current imbalances side-to-side in Q1062 during MIX mode operation). The Sweep Start Level connected to the base of Q1062A is not always a...

Output Buffer Amplifier

The Output Buffer Amplifier stage is a common-base amplifier with the signal current-driven into the emitter. It provides the output sawtooth current signal to the Horizontal Amplifier and provides a measure of isolation between the Sawtooth Generator and the Horizontal Amplifier. The HORIZ DISPLAY switch connects to this stage to control the A sawtooth output in the various horizontal modes of operation. In the A and A INTEN modes of operation, the A sweep signal passes through Q1038 to the...

Disconnect Amplifier

After holdoff but before the next sweep, Disconnect Amplifier Q1024 conducts current through R1024 and the timing resistor Rt. This prevents timing current from Sawtooth Output to Horizontal Amplifier Fig. 3-6. Detailed block diagram of the A Sweep Generator. Sawtooth Output to Horizontal Amplifier Fig. 3-6. Detailed block diagram of the A Sweep Generator. charging the timing capacitance Ct. The positive-going sweep start gate from Q864 turns off Q1024 and the timing current now begins to...

And B Sweep Generators

Q650 and Q652 are common-emitter amplifier stages that provide the signal currents necessary to switch the triggering tunnel diodes. CR650 and CR652 are 4.7 mA tunnel diodes. Quiescently (i.e., after the sweep holdoff period has passed, but before triggering), CR650 and CR652 are biased into their low voltage states. Q650 cannot provide sufficient current to switch CR650 to its high voltage state. Q652, however, can provide sufficient current to bias CR652 into its high voltage state when Q652...

Trigger Coupling

The Trigger COUPLING switches offer a means of accepting or rejecting certain components of the trigger signal. In the AC, LF REJ, and HF REJ mode of trigger coupling, the DC component of the trigger signal is blocked by coupling capacitors C612 or C611. Frequency components below about 60 Hz are attenuated when using AC or HF REJ coupling and below about 15 kHz when using LF REJ coupling. The higher frequency components of the trigger signal are passed without attenuation. In the HF REJ mode...

A And B Trigger Generators General

The Trigger Generator circuits produce trigger pulses to start the Sweep Generator circuits. These trigger pulses are derived either from the internal trigger signal from the vertical deflection system, an external signal connected to the external trigger input connectors, or a sample of the line voltage applied to the instrument. Controls are provided in each circuit to select trigger level, slope, coupling, and source. Since the A and B Trigger Generator circuits are virtually the same, only...

Normal Trigger Pickoff Amplifier

The trigger signal for NORM trigger operation is obtained from the collector of Q322. Normal Trigger DC Adjustment R340 sets the DC level of the normal trigger output signal so the sweep is triggered at the 0 level of the displayed signal when the Triggering LEVEL control is set to 0. Q344 and Q346 are connected as a feedback amplifier with the signal applied to the non-inverting input and the feedback connected between the output and the inverting input. Gain of the stage is approximately

Delay Line Driver

The outputs from the Diode Gate stages are applied to the Delay-Line Driver stage composed of Q322 and Q324. Q322 and Q324 are connected as feedback amplifiers with R325 and R327 providing feedback from the collector to the base of their respective transistors. A sample of the signal in the collector circuit of Q322 is used for triggering in the NORM mode of trigger operation. The BW LIMIT switch S338A connects a pi filter composed of C338, C339, L338, and L339 between the output signal lines...

Switching Multivibrator

In this mode of operation, the Switching Multivibrator operates as a bistable multivibrator. When the ALT pushbutton is pressed, -8 volts is applied to the emitter of Alternate Trace Switching Amplifier stage Q352 by the VERT MODE switch. Q352 is forward biased to supply current to the on Switching-Multivibrator transistor through R352 and CR368 or CR378. For example, if Q374 is conducting, current is supplied to Q374 through R352 and CR378. The current flow through...

Diode Gates

The Diode Gates, consisting of four diodes each, can be thought of as switches which allow either of the Vertical Channel 2 Display Only. When the CH 2 pushbutton is pressed, the above conditions are reversed. The junction of CR305-CR307 is connected to -8 volts through R376 and Chopped Blanking To Z-Axis Amplifier Fig. 3-4. Detailed block diagram of the Vertical Switching Circuit. Chopped Blanking To Z-Axis Amplifier Fig. 3-4. Detailed block diagram of the Vertical Switching Circuit. the...

Third Cascode Amplifier

The trigger pickoff circuit only provides a signal to one emitter follower. This emitter follower (Q262) in turn provides the trigger signal to the Trigger Generator circuits in the CH 2 positions of the SOURCE switches. Preamp output signals to be coupled to the Vertical Output Amplifier. CR304, CR305, CR307 and CR308 control the Channel 1 output and CR314, CR315, CR317 and CR318 control the Channel 2 output. These diodes are in turn controlled by the Switching Multivibrator for dual trace...

First Cascode Amplifier Stage

The Paraphase Amplifier Stage composed of Q32 and Q36 converts the single-ended input signal into a push-pull output signal. C33, C34 and CR34 optimize high frequency response through the amplifier stage. R37 and R38 provide thermal balance for the amplifier. C37 and C38 minimize Miller effect through 032 and Q36. Step Atten Bal adjustment R25 adjusts for no baseline shift of a CRT display when switching between adjacent positions of the VOLTS DIV switch. The Common Base Amplifier stage...

Scale Factor Switching Circuit

The vertical deflection factor for each channel is indicated by back-lighting the appropriate figures imprinted on the flange of the VOLTS DIV knob. When a X1 probe is connected to the CH 1 OR X input connector, the base level of transistor Q386 is determined by the voltage divider composed of R384, R383 and X10 display factor bulb DS382. Q386 is biased into saturation and conducts current through the X1 indicator DS386. When Q386 conducts, the voltage level at its collector is very close to +5...

Input Attenuator

The effective overall deflection factor of each channel of the 465 is determined by the appropriate VOLT DIV switch. The basic deflection factor of the Vertical Deflection System is 5 mV division of CRT deflection. To achieve the deflection factor values indicated on the front panel, precision attenuators are switched in to the circuit and the gain of the First Cascode Amplifier stage is changed. For the VOLT DIV switch positions above 5 mV, attenuators are switched in to the circuit, singly or...

Input Coupling

Signals applied to the input connector can be AC coupled, DC coupled, or internally disconnected from the input to the Vertical Input Amplifier circuits. When the Input Coupling switch S5 is set for DC coupling, the input signal is coupled directly to the Input Attenuator stage. When AC coupled, the input signal passes through capacitor C3. This capacitor prevents the DC component of the signal Fig. 3-2. Detailed block diagram of the Channel 1 Preamplifier. from passing to the amplifier. In the...

General

The following discussion is provided to aid in understanding the overall concept of the 465 Oscilloscope before the individual circuits are discussed in detail. A basic block diagram of the 465 Oscilloscope is shown in Fig. 3-1. Only the basic interconnections between the individual blocks are shown on this diagram. Each block represents a major circuit within the instrument. The number on each block refers to the complete circuit diagram which is located at the rear of this manual. Signals to...

Delayed Sweep Displays

Preset the instrument controls and follow steps 1 through 6 for obtaining a Normal Sweep Display. 2. Set the HORIZ DISPLAY switch to A INT and the B Trigger SOURCE switch to STARTS AFTER DELAY. 3. Pull out the B TIME DIV switch knob and turn clockwise so the intensified zone on the display is the desired length. Adjust the INTENSITY control to achieve the desired display brightness. 4. Adjust the DELAY-TIME POSITION dial to position the intensified zone to the portion of the display to be...

Magnified Sweep Display

Preset the instrument controls and follow steps 1 through 6 for obtaining a Normal Sweep Display. 2. Adjust the horizontal POSITION control to move the area to be magnified to within the center graticule division of the CRT. If necessary, change the TIME DIV switch setting so the complete area to be magnified is within the center division. 3. Set the X10 MAG switch to the on position (button in) and adjust the horizontal POSITION control for precise positioning of the magnified display.

Component Replacement

Tektronix 465

Always disconnect the instrument from the power source before attempting to replace components. Circuit Board Replacement. Occasionally it may be necessary to gain access to the reverse side of a circuit board or to remove one circuit board to gain access to another. The following procedures outline the necessary steps to facilitate instrument disassembly. Most of the connections to the circuit boards in the instrument are made with pin connectors. However, some connections are soldered to the...

Cathode Ray Tube CRT and Display

BEAM FIND Compresses the display to within the graticule area, independently of display position or applied signals. INTENSITY Controls brightness of the display. FOCUS Provides adjustment for optimum SCALE ILLUM Controls graticule brightness. Controls the vertical position of the trace. In the X-Y mode of operation, the CH 2 control positions on the Y-axis vertically and the Horizontal POSITION control positions on the X-axis horizontally . Input connector for Channel 1 deflection signals or...

Sweep Latch

0822 and Q828 compose the B Sweep Latch. Quiescently, before either the A or B Sweeps have reached their maximum amplitudes both transistors are off. Then, the sweep reset pulse from whichever sweep terminates first will be applied to the base of Q828 A Sweep reset through CR826 B Sweep reset through CR825 .The positive-going reset pulse turns on Q828 and the negative-going movement at its collector turns on Q822. The collector of Q822 in turn pulls up on the base of Q828, holding Q828 on,...

Paraphase Amplifier

U640 is a paraphase amplifier stage that converts the single-ended input from Source Follower Q622 into a push-pull output applied to the tunnel diode driver stage. Trigger Level Centering adjustment R635 sets the level at pins 14 and 15 of U640 so that the display is correctly triggered when the LEVEL control is centered. The LEVEL control varies the level at pins 14 and 15 of U640 to select the point on a trigger signal where triggering occurs. The slope of the input signal that triggers the...

DC Restorer Circuit

C1488, C1487, CR1487, CR1488, and R1486 form a DC restorer circuit. All DC levels in this circuit are referenced to the negative potential of the CRT cathode. The voltage difference across R1486 approximately equals the voltage swing present at the junction of CR1482 and CR1483. The control grid end of R1486 is more negative than the end connected to CR1488. The amplitude of the voltage swings present at the junction of CR 1482 and CR1483 is determined by the voltage levels established by the...

Axis Amplifier

In all positions of the TIME DIV switches except X-Y, the input signal to the base of Q1224 will be the sawtooth waveforms from the sweep generators. In the X-Y mode however, the sweeps are disabled and the signal applied to Q1224 comes from the Channel 1 Preamp via the X-Axis Amplifier stage. This stage includes Q1214, Q1218, and their associated circuitry. Fig. 3-7. Detailed block diagram of the Horizontal Amplifier. Fig. 3-7. Detailed block diagram of the Horizontal Amplifier. Q1214 is...

Obtaining Replacement Parts

All electrical and mechanical part replacements for the 465 can be obtained through your local TEKTRONIX Field Office or representative. However, many of the standard electronic components can be t obtained locally in less time than is required to order them from Tektronix, Inc. Before purchasing or ordering replacement parts, check the parts list for value, tolerance, rating, j and description. When selecting replacement parts, it is important to remember that the physical size...

A and B Sweep

Determines the operating mode for the A Trigger Circuit. AUTO With the proper trigger control settings, A Sweep can be initiated by signals that have repetition rates above about 20 hertz and are within the frequency range selected by the COUPLING switch. In the absence of an adequate trigger signal or when the trigger controls are misadjusted, the sweep free-runs to produce a reference trace. NORM With the proper trigger control settings, A Sweep can be initiated by signals that are within the...

High Voltage Rectifiers and Output

The high-voltage transformer T1420 has two output windings. One winding provides filament voltage for the cathode-ray tube. The filament voltage can be supplied from the High-Voltage Supply, since the cathode-ray tube has a very low filament current drain. The cathode and filament of the CRT are connected together to elevate the filament and prevent cathode-to-filament breakdown. One high-voltage winding provides both the negative cathode potential and the positive anode accelerating voltage....

Horizontal Sweep Controls

TIME DIV Switches A TIME DIV VAR HORIZ DISPLAY Switch X10 MAG Switch POSITION Control Locked together at 1 ms Calibrated detent A 1. Set the POWER switch to on button out . Allow several minutes for instrument warmup. 2. Connect the external signal to the CH 1 input connector. 3. Advance the INTENSITY control until the display is visible. If the display is not visible with the INTENSITY control at midrange, press the BEAM FIND pushbutton and adjust the CH 1 VOLTS DIV switch until the display is...

Cabinet

Part No. Eff Dscont 437-0141-00 348-0080-01 352-0263-00 200-1412-00 200-0602-00 367-0140-03 334-1998-00 214-0516-00 214-0513-00 214-0513-04 214-0515-00 214-0515-02 2 COVER,HINGE 80009 1 HANDLE, CARRYING 80009 4 SCREW,MACHINE 6-32 X 0.50 100 DEG,FLH STL 83385 OBD 2 SPRING,HLCPS 0.959 DIA X 1.250 INCH LONG 80009 2 INDEX,HDL RING 80009 2 INDEX,HDL RING 80009 2 GEAR,HDL INDEX 80009 2 GEAR,HDL INDEX 80009 1 WASHER,FLAT 0.204 ID X 0.438 INCH OD,STL 12327 1...

Cabinet Removal

Dangerous potentials exist at several points throughout this instrument. When the instrument is operated with the cover removed, do not touch exposed connections or components. Some transistors may have elevated cases. Disconnect power before cleaning the Instrument or replacing parts. The instrument wrap-around cabinet can be removed in the following manner 1. Unwrap the power cord from the instrument feet. 2. Remove the six screws indicated in Fig. 4-1 and remove the instrument feet and rear...

Second Cascode Amplifier

Transistors Q102-Q122 and Q104-Q124 constitute the Second Cascode Amplifier stage of the Channel 1 vertical preamplifier. Gain adjust R118 sets the overall gain of the Channel 1 vertical preamplifier by adjusting the signal current into the emitters of Q122 and 0124. The VAR control R112, when rotated out of the calibrated detent position, also adjusts the signal currents into Q122 and Q124 to provide uncalibrated deflection factors between the calibrated settings of the VOLTS DIV switch....

CRT Control Circuits

Focus of the CRT display is controlled by FOCUS control R1430. ASTIG adjustment R1445, which is used in conjunction with the FOCUS control to provide a well-defined display, varies the positive level on the astigmatism grid. Geometry adjustment R1442 varies the positive level on the horizontal deflection plate shields to control the overall geometry of the display. Two adjustments control the trace alignment by varying the magnetic field around the CRT. Y Axis adjustment R1446 controls the...