Telequipment D67 - User Manual

The Telequipment D67 is a 25 MHz, all solid-state dual-trace oscilloscope designed to provide a bright and clear display on its 8 x 10 cm mesh Cathode Ray Tube (CRT). This instrument is built for versatility and accuracy in waveform analysis, featuring a dual-trace vertical system that can display either channel separately, add channels algebraically, alternate between channels, or chop between channels at an 80 kHz rate. Its solid-state design, incorporating FET input circuitry, ensures minimum drift and fast stabilization time, making it suitable for examining complex waveforms and precise time measurements.

Function Description:

The D67's core function is to visualize electrical signals over time. The vertical system handles input signals, offering two independent channels (CH1 and CH2) that can be displayed in various modes:

• Channel 1 only: Displays the signal from the first input.
• Channel 2 only: Displays the signal from the second input, which can also be inverted.
• Alternate: Switches between displaying CH1 and CH2 on successive sweeps, ideal for higher sweep speeds.
• Chopped: Rapidly switches between CH1 and CH2 at an 80 kHz rate within a single sweep, suitable for lower sweep speeds.
• Summed: Displays the algebraic sum of CH1 and CH2. If CH2 is inverted, this mode shows the difference between the two signals.

The horizontal system controls the time axis of the display, offering both main (A) and delayed (B) sweeps. The delayed sweep feature is particularly useful for magnifying specific portions of a complex waveform, allowing for detailed examination and accurate time measurements. Sweep display modes include:

• A only: Displays only the main sweep.
• A intensified by B: Displays the main sweep with a brighter portion indicating the segment that would be expanded by the delayed sweep.
• B delayed by A: Displays only the expanded portion of the waveform as defined by the delayed sweep.
• Single-shot: Captures non-recurrent signals, displaying a single sweep each time the RESET button is pressed.

Triggering ensures stable displays of repetitive waveforms. The D67 supports internal triggering from CH1, CH2, or an alternate source, as well as external triggering. Trigger modes include automatic, normal, TV field/line, and HF for high-frequency signals, with adjustable trigger level and polarity.

Important Technical Specifications:

• Vertical System:
  • Bandwidth: DC to 25 MHz (DC coupled), 2 Hz to 25 MHz (AC coupled).
  • Risetime: 14 ns nominal.
  • Deflection Factors: 10 mV/div to 50 V/div (calibrated accuracy ±3%). Variable control extends sensitivity up to 125 V/div.
  • Signal Delay: 200 ns.
  • Input Impedance: 1 MΩ and 39 pF approx.
  • Maximum Input: 400 V peak (DC, AC, & Sum).
• Horizontal System:
  • Sweep Rates (A and B sweeps): 2 s/div to 200 ns/div (calibrated accuracy ±3%). With x5 expansion, rates extend to 400 ms/div to 40 ns/div (±5%). Variable control allows continuous adjustment between steps.
  • External Horizontal Amplifier:
    • Bandwidth: DC to 1 MHz.
    • Risetime: 350 ns nominal.
    • Deflection Factors: 3 V/div approx. (600 mV/div approx. with x5 expansion).
    • Input Impedance: 1 MΩ and 30 pF approx.
    • Maximum Input: 400 V peak.
• Trigger System:
  • Internal Source: CH1, CH2, or alternate.
  • Internal Amplitude: 0.2 div (50 Hz - 5 MHz approx.), 0.2 div (10 Hz - 5 MHz approx.), 1 div (1 - 25 MHz approx.).
  • External Amplitude: 250 mV to ±15 V (at above frequencies).
  • External Impedance: 100 kΩ and 30 pF.
• Cathode Ray Tube (CRT):
  • Type: Single-gun with mesh PDA.
  • Display Area: 8 x 10 divisions.
  • Phosphor: P31 (standard), P7 or P11 options.
  • Overall Accelerating Potential: 10 kV approx.
• Power Requirements:
  • Voltage: 100-125 V (5 V steps), 200-250 V (10 V steps).
  • Frequency: 48-400 Hz.
  • Consumption: 50 VA approx.
• Physical:
  • Size: 24 cm (Height), 21 cm (Width), 44 cm (Depth).
  • Weight: 11.5 kg.
  • Cooling: Convection.
  • Temperature Limits (ambient): Operating -15 to +40°C, Non-operating -25 to +70°C.

Usage Features:

The D67 offers a comprehensive set of controls for precise waveform manipulation:

• CRT Controls: BRILLIANCE (on/off and intensity), FOCUS, ASTIG (for overall definition), TRACE ROT'N (aligns traces with graticule), and SCALE ILLUM (graticule intensity).
• Vertical Display Controls (CH1 & CH2): VOLTS/DIV (attenuation), VARIABLE (fine sensitivity adjustment), DC-GND-AC (input coupling), POSITION (vertical trace displacement), INVERT-NORMAL (CH2 polarity), and CHOP-ALT-SUM (display modes). INT TRIG buttons select internal triggering from either or both channels.
• Main Sweep A Controls: TIME/DIV (sweep speed), VARIABLE (free-running or triggered operation), LEVEL (trigger point selection), and TRIG MODE buttons (TV F/L, HF, polarity, INT/EXT, SINGLE SHOT).
• Delayed Sweep B Controls: TIME/DIV (delayed sweep speed), VARIABLE (gated/ungated operation), LEVEL (trigger point for gated mode), TRIG MODE buttons (TV L, polarity, INT/EXT).
• Horizontal Display Controls: POSITION (horizontal trace displacement), FINE (sensitive position and x5 horizontal gain), and DISPLAY (A, A Intensified by B, B Delayed by A modes).
• Front Panel Outputs: CALIBRATOR (500 mV squarewave at supply frequency for probe compensation and calibration), A SWEEP SAWTOOTH (positive-going ramp for external equipment), and GATE OUT (fast-edged negative-going rectangular pulses for A or B sweep duration).

Maintenance Features:

The D67 is designed for reliability with its solid-state components, minimizing the need for frequent internal adjustments. However, periodic checks are recommended to maintain measurement accuracy.

• Pre-operating Checks: Verify the rear voltage-selector plug matches local supply, check fuse rating (500 mA for 100-125 V, 250 mA for 200-250 V), and ensure proper supply lead color coding (Line: Brown/Black, Neutral: Blue/White, Earth: Green/Yellow/Green).
• Probe Compensation: Instructions are provided for compensating x10 probes using the CAL or GATE OUT sockets to achieve square corners on displayed waveforms.
• General Maintenance:
  • Sweep Speed Check: Verify sweep rates using the calibrator waveform.
  • Gain Check: Adjust vertical amplifier gain (R671 for CH1, R672 for CH2) to ensure accurate deflection factors.
  • Access to Interior: Detailed steps for removing cabinet sides and base cover plate are provided for internal access.
  • CRT Removal & Replacement: Instructions for safely removing and replacing the CRT, including unplugging connectors and transferring components like the TRACE ROT'N coil.
• Calibration: A full calibration procedure is outlined, including:
  • Preliminary Steps: Disconnecting from supply, setting internal presets to mid-position, measuring stabilized line resistances.
  • Power Supply Calibration: Adjusting potentiometers (R436, R431, R421, R404) for +12 V, -12 V, +115 V, and CRT cathode voltages.
  • Initial Settings: Adjusting CRT and horizontal controls for a clear, free-running, and aligned trace.
  • Horizontal Amplifier Calibration: Setting mean X-plate potential (R297), horizontal DC balance (R292, R137), and external horizontal input compensation (C113).
  • CRT Calibration: Adjusting trace alignment (TRACE ROT'N) and geometry (R309).
  • Sweep Trigger A Calibration: Setting automatic A and trigger sensitivity (R12, R33), sweep length (R109), hold-off time (R113), timing (R143, C219A, C114), and stability (R125).
  • Sweep Trigger B Calibration: Setting trigger balance (R62, R82), horizontal balance (R187), sweep length (R165), hold-off time (R168), timing (R186, C219B), and stability (R179).
  • Vertical Amplifier Calibration: Setting CH1 and CH2 variable balance (R644, R647), position balance (R635, R636), gain (R671, R672), input capacitance (C621, C914, C630, C623, C631), attenuator compensation (C914, C916, C907, C913, C912, C906, C905, C904, C903, C902), neutralising (C639, C641, C642, C643), sum mode position balance (R630), high-frequency compensation (C646, C647, C649, C651, R699, R703, R706, L621, L622), and internal 500 mV calibrator (R414).

The manual emphasizes that for servicing, only suspect items should be returned, and the power supply plug should be removed to prevent transit damage.