To Next PageTo Next Page
Need help?Do you have a question about the Telequipment Serviscope S51A and is the answer not in the manual?
Describes the 5" flat-faced CRT, its phosphor, and filter for contrast enhancement.
Details the two-stage amplifier, input stage, and output stage configuration of the vertical amplifier.
Instructions for verifying and setting the correct supply voltage using internal links on the instrument.
Step-by-step guide for setting initial front panel controls for the oscilloscope's operation.
Automatic sweep triggering without manual level control, suitable for repetitive waveforms.
Explains the four positions of the trigger selector switch for various signal types and synchronization.
Socket for horizontal deflection amplifier input, suitable for 4-10V p.p signals and external signal application.
Socket connected to CRT cathode for trace brightening via negative pulses, with specified time constant.
Image illustrating the layout of controls on the front panel of the Serviscope, showing key adjustment knobs.
Explains the triode stages, gain control, and output connections of the vertical amplifier circuitry.
Details the trigger selection switches and bistable switch for signal synchronization within the trigger circuit.
Instructions for adjusting input attenuator compensation using a squarewave generator for accurate signal measurement.
Lists abbreviations for capacitor and resistor types used in the components list for clarity.
Lists capacitor types with their corresponding abbreviations as used in the components list.
Lists resistor types with their corresponding abbreviations as used in the components list.
The Serviscope Type S51 is a general-purpose oscilloscope produced by Telequipment Limited. This instrument is designed for a wide range of laboratory applications, offering continuous development and improvement to its users. The S51 is available in three versions: S51A, S51E, and S51T, each with slight variations in features to cater to different user needs.
The core of the S51 is its 5-inch flat-faced Cathode Ray Tube (CRT), which operates at 3 Kv overall, providing an exceptionally bright and fine trace across an 8 cm x 8 cm working area. A Pl phosphor is typically supplied, but a long-persistence tube can be specified for particular applications. To enhance contrast, especially in high ambient light conditions, a green filter is incorporated.
The vertical deflection amplifier is a two-stage design. It features a cathode-coupled input stage, whose output drives a cathode follower, followed by an output stage configured as a long-tailed pair. The signal is fed to one grid, while a DC shift voltage is applied to the other, allowing for precise vertical positioning of the trace. The amplifier boasts a sensitivity of 100mV/cm and a bandwidth of DC to approximately 3 Mc/s (-3dB). An input attenuator with nine positions is frequency compensated, offering sensitivities ranging from 100mV to 50V per cm. The input impedance is 1 megohm, shunted by about 30 pf.
The sweep circuit employs a Miller run-down generator, providing six preset sweep speeds from 1 µsec/cm to 100Msec/cm. A variable control offers a 10:1 range, enabling overlap between fixed ranges and extending the slowest sweep to 1 sec/cm. The horizontal amplifier includes an X GAIN control that expands the trace up to approximately two times. Sufficient shift is provided to center any part of the expanded trace on the screen. Trace unblanking is achieved through DC coupling of the unblanking waveform, ensuring uniform trace brightness across all sweep speeds and completely eliminating time base flyback.
Triggering is a key feature of the S51, offering two modes: AUTO and TRIGGER LEVEL SELECTION. In AUTO mode, the sweep free-runs at a slow speed when no input signal is present, but automatically triggers upon signal application. This mode is suitable for approximately 90% of normal laboratory uses, especially for repetitive waveforms between 50 c/s and 1 Mc/s with an amplitude exceeding 2 mm. The TRIGGER LEVEL SELECTION mode, activated by turning the AUTO switch OFF, allows users to trigger the sweep at any point on the input waveform. The circuit triggers internally on 2 mm of displayed signal and externally (except for the S51E version) from 3V peak-to-peak.
For specific applications, the S51A and S51T versions include a built-in TV sync integrator circuit. This enables triggering of the sweep from the Frame pulses of a composite Television waveform. The integrating circuit can also be useful for frequency discrimination, acting as a low-pass filter for audio signals with high-frequency noise. External triggering is also supported by connecting a signal to the external trigger socket.
Rear connectors provide access to the Horizontal Amplifier (X-Amp Input) and for intensity modulation of the beam (Z. Mod). The X-Amp Input is suitable for signals between 4 and 10 volts p.p., with the X-GAIN control offering a 2 to 1 variation of gain. The input impedance for this is about 500 K with an input capacity of about 100 pf, and a frequency response of 3 dB down at 5 cycles and about 200 Kc/s. The Z. Mod socket, connected to the CRT cathode via a blocking capacitor, allows a negative pulse to brighten the trace, with a time constant of 0.01 mf and 10,000 ohms.
The S51 is cooled by convection, with air entering the bottom of the case, drawn up past the tubes and other hot components, and exiting through top slots. Proper airflow is crucial for optimal operation, and users are advised not to obstruct the air flow or place anything on top of the instrument.
For first-time operation, users are guided through checking the supply voltage, which can be configured for 110V or 220V by soldering appropriate links. A simplified method is provided for quick setup, involving setting the input switch to A.C., warming up the instrument, adjusting BRILLIANCE and FOCUS for a sharp trace, and backing off the STABILITY control until the time base stops. For more advanced use, detailed instructions are given for understanding and utilizing each control, including Y SHIFT, BRILLIANCE, X GAIN, X SHIFT, STABILITY, TRIGGER LEVEL, TIME/CM, and TRIG. SELECTOR.
Maintenance and adjustments are designed to be straightforward due to the S51's reliable circuitry. Most servicing is limited to replacing defective tubes, which generally have minimal impact on performance, especially in the vertical amplifier. For the sweep generator and horizontal amplifier, tubes are not particularly critical. However, if internal preset controls require adjustment, detailed instructions are provided for input attenuator compensation using a squarewave generator, vertical amplifier high-frequency compensation (requiring a high-accuracy squarewave generator), and trigger circuit sensitivity adjustment. Specific steps are also outlined for a complete readjustment of the sweep generator and horizontal amplifier, including trace centering and time/cm calibration. The CRT circuit includes a preset for inter-deflector plate shield adjustment to correct pin cushion and barrel pattern distortion. High impedance probe compensation is also detailed, requiring a squarewave generator for adjustment.
The manual includes a comprehensive components list with abbreviations for capacitor and resistor types, along with their values, descriptions, tolerances, and ratings. This list is crucial for ordering exact replacements, which are recommended for optimal performance. Circuit voltages are provided in the circuit diagram, with measurements taken in the absence of a 'Y' signal and with the time base set to 1 mS/cm, level to Auto, stability fully clockwise, and trace centered. These measurements are corrected for meter loading errors and were obtained using an "Avo" model '8' 20,000 ohms per volt instrument.
General| Type | Oscilloscope |
|---|---|
| Bandwidth | 5 MHz |
| Input Impedance | 1 MΩ |
| Input Capacitance | 30 pF |
| Input Sensitivity | 5 mV/div to 20 V/div |
| Timebase | 0.2 μs/div to 0.5 s/div |
| Trigger Modes | Auto, Normal, Single |
| Display | CRT |
| CRT Size | 6 cm |
| Power Supply | AC Mains |
| Deflection Sensitivity | 5 mV/div to 20 V/div |
