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...

Instrument Repackaging

If this instrument is to be shipped for long distances by commercial means of transportation, it is recommended that it be repackaged in the original manner for maximum protection. The original shipping carton can be saved and used for this purpose. Fig. 5 in the Mechanical Parts List illustrates how to repackage the 465 and gives the part number for the packaging components. New shipping cartons can be obtained from Tektronix, Inc. Contact your local TEKTRONIX Field Office or representative.

Calibrated Sweep Accuracy

Unmagnified sweep accuracy is 2 from +20 C to +30 C (+68 F to +86 F) and 3 from -15 C to +20 C and +30 C to +55 C (+5 F to +68 F and +86 F to +131 F). For the same temperature ranges, magnified sweep accuracy is 3 and 4 respectively. Exclude the first and last 50 ns of the 5 ns, 10 ns, and 20 ns magnified sweep rates. Accuracy specifications apply over full ten divisions unless otherwise specified. Sweep accuracy, over any two or less division portion of the sweep, is 5 . Exclude the first and...

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...

Soldering Techniques

Always disconnect the instrument from the power source before attempting to solder in the instrument. Ordinary 60 40 solder and a 35- to 40-watt pencil-type soldering iron can be used to accomplish the majority of the soldering to be done in the 465. If a higher wattage-rating soldering iron is used on the etched circuit boards, excessive heat can cause the etched circuit wiring to separate from the board base material. The Vertical Preamplifier Attenuator circuit boards are made of material...

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...

General

The Low-Voltage Power Supply circuit provides the operating power for this instrument from four regulated supplies and one unregulated supply. Electronic regulation is used to provide stable, low-ripple output voltages. Fig. 3-11 shows a detailed block diagram of the Power Supply circuit. A schematic of this circuit is shown at the back of this manual. Fig. 3-11. Detailed block diagram of the Low Voltage Power Supply. Fig. 3-11. Detailed block diagram of the Low Voltage Power Supply.

Amplifier

The amplifier consists of two emitter-coupled push-pull amplifier stages. The emitter source voltage for Q672 and Q682 is switched on and off by the TRIG VIEW pushbutton. With the TRIG VIEW pushbutton not pressed, the emitters of Q672 and Q682 are returned to -8 volts through R691. This reverse-biases the base-emitter junctions of the transistors, preventing any loading of the A Trigger Generator circuit. When the TRIG VIEW pushbutton is pressed, the emitters of Q672 and Q682 are returned to...

Output Amplifier

The output signal from the Multivibrator overdrives Output Amplifier Q1598 to produce an accurate square wave at the output. When the base of Q1598 goes positive Q1598 is cut off and the collector level drops down to ground. When the base goes negative Q1598 is biased into saturation and the collector of Q1598 rises positive to about +5 volts. Amplitude adjustment R1597 adjusts the resistance between the collector of Q1598 and ground to determine the amount of current allowed to flow, which in...

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

Q804 is the B Sweep Holdoff Amplifier. Its circuit action is identical to that described for the A Sweep Holdoff Amplifier except that there are three gate signal sources that control the state of the stage. The three sources are the holdoff gate from pin 17 of U870 (through CR859), the collector of Q1052 in the Delay Pickoff Comparator, and the collector of Q822 in the B Latch Multivibrator (through CR809). All three gate sources must be in their LO state for B Sweep to be triggerable any one...

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...

Reference Feedback Amplifier

Reference Feedback stage Q332 provides common mode voltage feedback from the Delay-Line Driver stage to allow the diode gates to be switched with a minimum amplitude switching signal. The emitter level of Q332 is connected to the junction of the Switching Multivibrator collector resistors, R371 and R361 through CR372 or CR362. The collector level of the on Switching Multivibrator transistor is negative and either CR362 or CR372 is forward biased. This clamps the cathode level of the forward...

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...

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...

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...

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...

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....

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...

Calibrator and Power

A combination current loop and square-wave voltage output device. Provides a 30 mA square-wave current, 300 mV square-wave voltage signal with a repetition rate of approximately 1 kHz. Light that indicates the applied line voltage is below the lower limit of the regulating range selected by the Regulating Range Selector assembly. Output connector providing a positive-going rectangular pulse coincident with the A sweep time. Output connector providing a positive-going rectangular pulse...