Heathkit Model OP-1

Professional Oscilloscope

Date Calibrated:   _____/_____/_____

Calibration Procedure

· Disconnect all external cables, components, and wires from the output terminals.

· All controls and switches are described as labeled on either the instrument or the schematic diagram.

Ancillary Equipment Needed

1 MHz Square Wave Generator

Audio Generator

Frequency Counter

VTVM

* * * * * * *

TUBE REMOVAL SETUP

Refer to top illustration

Operation Manual, page 28

(    )         Remove the 12BH7 tube from socket V-4.

(    )         Remove the 12BH7 tube from socket V-16.

(    )         Remove the OB2 tube from socket V-10.

* * * * * * *

FRONT PANEL INITIAL SETUP

Refer to photo

Operation Manual, page 15

(    )         Adjust both the INTENSITY and SCALE ILLUMINATION controls (R71 & R54) to the center of rotation.

(    )         Adjust both the FOCUS and ASTIGMATISM controls (R73 & R77) to the center of rotation.

(    )         Adjust both the VERTICAL CENTERING and HORIZONTAL CENTERING controls (R13 & R48) to the center of rotation.

(    )         Adjust the VERTICAL GAIN control (R7) to full counter-clockwise.

(    )         Set the TRIGGER SELECTOR switch to the HIGH FREQ position.

(    )         Adjust the STABILITY control (R35) to full counter-clockwise.

(    )         Set the horizontal TRIGGER SELECTOR switch to the HOR INPUT position.

(    )         Adjust the TRIGGERING LEVEL control (R24) to full counter-clockwise.

(    )         Set the vertical AC-DC switch to the DC position.

(    )         Set the VERTICAL ATTENUATOR switch to the 50 volts/cm position.

(    )         Adjust the VARIABLE MULTIPLIER control (R38) to the 5 position.

(    )         Set the STABILITY CONTROL switch to the 2 ms/cm position.

(    )         Turn the PHASING control (R42) counter-clockwise to the AC OFF position.

(    )         Set the HORIZONTAL MULTIPLIER switch to the 1 DC position.

(    )         Adjust the HORIZONTAL GAIN control (R51) to full counter-clockwise.

(    )^?        Adjust the vertical DC BALANCE control (R6) – position unimportant.

(    )^?        Adjust the horizontal DC BALANCE control (R46) – position unimportant.

* * * * * * *

INTERNAL INITIAL SETUP

Bottom chassis plate [top photo]

Operation Manual, page 16

(    )         Adjust the H. V. ADJUST control (R69) to the center of rotation.

(    )         Adjust the AC TRIGGER ADJUST control (R26) to the center of rotation.

(    )         Adjust the TRIGGER SENSITIVITY control (R27) to the center of rotation.

(    )         Adjust the SWEEP CALIBRATION control (R41) to the center of rotation.

(    )         Adjust the SWEEP RANGE control (R40) to the center of rotation.

(    )^?        Adjust the SWEEP POSITIONING control (R68) – position unimportant.

(    )^?        Adjust the HIGH FREQUENCY SWEEP ADJUST trimmer (C26) [behind front panel] – position unimportant.

* * * * * * *

Vertical Amp Setup

Left side of chassis [bottom photo]

Operation Manual, page 16

(    )         Adjust the VERTICAL RANGE control (R11) to the center of rotation.

(    )^?        Adjust the vertical HIGH FREQUENCY trimmer (C102) – position unimportant.

(    )^?        Adjust the vertical COMPENSATION trimmers (C2 & C3) – position unimportant.

* * * * * * *

Calibration Start

(    )         Connect the line cord to the AC power lines.

(    )         Turn the PHASING control clockwise to the ON position.

               (Allow the instrument to warm up for 15 minutes)

(    )         Adjust the INTENSITY control until the spot is just visible.

(    )         Voltage Regulator tubes V17, V18, V19, V21, & V22 should be glowing.

(    )         Neon bulb (V23) [left side of chassis] should be lit.

* * * * * * *

DC Balance Adjustments

Front Panel

(    )         Connect the VTVM’s common lead to the chassis.

(    )         Set the VTVM function switch to the DC+ position.

(    )         Set the VTVM’s range switch to the 150-volts scale position.

(    )         Connect the VTVM’s test probe to the center lug of the vertical DC BALANCE control (R6) [front panel].

(    )         Adjust the DC BALANCE control until a reading of 0 volts is obtained.

· Decrement the meter’s range switch as the voltage decreases.

(    )         Disconnect the test probe.

(    )         Set the VTVM’s range switch to the 150-volts scale position.

(    )         Connect the VTVM’s test probe to the center lug of the horizontal DC BALANCE control (R46) [front panel].

(    )         Adjust the DC BALANCE control until a reading of 0 volts is obtained.

· Decrement the meter’s range switch as the voltage decreases.

(    )         Disconnect the test probe.

* * * * * * *

Sweep Positioning Adjustment

Bottom chassis plate [top photo]

Operation Manual, page 16

(    )         Set the VTVM’s range switch to the 150-volts scale position.

(    )         Connect the VTVM’s test probe to the center lug of the SWEEP POSITIONING control (R68).

(    )         Adjust the SWEEP POSITIONING control until a reading of 0 volts is obtained.

· Decrement the meter’s range switch as the voltage decreases.

(    )         Disconnect the test probe.

* * * * * * *

Tube Installation

Refer to top illustration

Operation Manual, page 28

(    )         Turn the PHASING control counter-clockwise to the AC OFF position.

(    )         Install a 12BH7 tube into socket V-4.

(    )         Install a 12BH7 tube into socket V-16.

(    )         Install an OB2 tube into socket V-10.

* * * * * * *

Trace Adjustment

(    )         Turn the PHASING control clockwise to the ON position.

               (Allow the instrument to warm up for 5 minutes)

(    )         Adjust the VERTICAL RANGE control (R11) [left side of chassis] until the spot is in the middle of the display.

(    )         Adjust both the FOCUS and ASTIGMATISM controls (R73 & R77) for the smallest spot size.

(    )         Adjust the INTENSITY control (R71) until the spot is just visible.

(    )         Adjust the HORIZONTAL GAIN control (R51) to full clockwise.

(    )         Connect a test lead to the horizontal input binding post.

(    )         Connect the same test lead to either pin 3 or 4 of the 6C4 tube (V-14).

(    )         A horizontal trace should appear.

(    )         Horizontal trace should be parallel with the horizontal graticule lines.

(    )         If trace is parallel with graticule lines, skip down to next double asterisk marked instruction.

(    )₁        Note the relative position of the trace.

(    )₂        Turn the PHASING control counter-clockwise to the AC OFF position.

(    )₃        Loosen the CRT clamps.

(    )₄        Rotate the CRT tube until the trace is parallel with the graticule lines.

(    )₅        Tighten the CRT clamps.

(    )₆        Turn the PHASING control clockwise to the ON position.

               (Allow the instrument to warm up for 5 minutes)

· Repeat the above six steps * until the trace is parallel with the graticule lines.

(    )**      Disconnect the test lead from both the 6C4 tube and the binding post.

* * * * * * *

Horizontal Sweep Adjustment

(    )         Adjust the HORIZONTAL GAIN control (R51) to full counter-clockwise.

(    )         Note the position of the spot.

(    )         Adjust the HORIZONTAL GAIN control to full clockwise.

(    )         If the spot moved, adjust the horizontal DC BALANCE control (R46) until the spot returns to its original position.

(    )         Set the horizontal TRIGGERING LEVEL switch to the INT – position.

(    )         Adjust the STABILITY control (R35) to full clockwise.

(    )         A horizontal trace should appear.

(    )         Adjust the HORIZONTAL CENTERING control (R48) to center the trace.

(    )         Adjust the HORIZONTAL GAIN control (R51) until the trace is 10 cm long [full screen width].

(    )         Set the HORIZONTAL MULTIPLIER switch to the 5 DC position.

(    )         Adjust the HORIZONTAL CENTERING control (R48) from full clockwise to full counter-clockwise.

(    )         If the entire trace can be centered, skip down to next double asterisk ** marked instruction.

(    )         Adjust the HORIZONTAL CENTERING control to the center of rotation.

(    )         Adjust the SWEEP POSITIONING control (R68) [bottom chassis plate] until the trace is centered.

(    )**      Adjust the vertical DC BALANCE control (R6) as described in the DC Balance Adjustments section above.

* * * * * * *

Vertical Gain Adjustment

(    )         Adjust the VERTICAL GAIN control (R7) to full counter-clockwise.

(    )         Note the trace position.

(    )         Adjust the VERTICAL GAIN control to full clockwise.

(    )         If the trace has moved, adjust the vertical DC BALANCE control (R6) until the trace is at its noted position above.

* * * * * * *

Internal Trigger Sweep Adjustment

(    )         Set the TRIGGER SELECTOR switch to the DC position.

(    )         Adjust the STABILITY control (R35) to full counter-clockwise.

(    )         Adjust the TRIGGERING LEVEL control (R24) to full counter-clockwise.

(    )         Adjust the STABILITY control clockwise until a trace appears.

(    )         Adjust the STABILITY control counter-clockwise until the trace just disappears.

· DO NOT readjust the STABILITY control unless instructed to do so.

 (    )₁       Adjust the TRIGGERING LEVEL control (R24) clockwise until a trace just appears.

(    )₂        Adjust the TRIGGER SENSITIVITY control (R27) [bottom chassis plate] clockwise until the trace just disappears.

(    )         Repeat the above two steps * until no continuous trace occurs at any setting of the TRIGGERING LEVEL control (R24).

* * * * * * *

Vertical Triggering Level Adjustment

(    )         Connect a test lead to the vertical input.

(    )         Connect the same test lead to either pin 3 or 4 of the 6C4 tube (V-2).

(    )         Set the VERTICAL ATTENUATOR switch to the 2 volts/cm position.

(    )         Adjust the VERTICAL GAIN control (R7) for a trace 3 – 4 cm high.

(    )         Adjust the TRIGGERING LEVEL control (R24) until a trace appears.

· Rotation of the Triggering Level control changes the start position of the trace.

(    )         Set the TRIGGER SELECTOR switch to the AC position.

(    )         Adjust the AC TRIGGER ADJUST control (R26) [bottom chassis plate] until the trace just appears and the starting point (left edge) is exactly the same spot before in the DC switch position.

· This adjustment is sensitive, until the control is properly adjusted, no trace will be present.

(    )         Set the horizontal TRIGGER SELECTOR switch to the INT + position.

(    )         Adjust the TRIGGERING LEVEL control (R24) until a trace appears.

· Operation should be exactly the same as in the INT – position, except for a start slope change.

(    )         Disconnect the test lead from the 6C4 tube only.

* * * * * * *

External Triggering Adjustment

(    )         Set the horizontal TRIGGERING SELECTOR switch to the EXT TRIGGER – position.

(    )         Connect the same test lead to the EXT TRIGGER input [front panel].

· The operation of the STABILITY control (R35) and the TRIGGERING LEVEL control (R24) remain the same.

(    )         Disconnect the test lead from both the vertical and EXT TRIGGER inputs.

* * * * * * *

Trigger Sensitivity Adjustment

(    )         Set the TRIGGER SELECTOR switch to the AC AUTO position.

· If no trace is present, skip the next step.

(    )         Adjust the TRIGGER SENSITIVITY control (R27) [bottom chassis plate] clockwise until the trace just disappears.

(    )         Adjust the TRIGGER SENSITIVITY control counter-clockwise until the trace just appears.

* * * * * * *

Vertical Input Calibration

(    )         Set the TRIGGER SELECTOR switch to the AC AUTO position.

(    )         Remove the knob on the VERTICAL GAIN control (R7).

(    )         Set the VERTICAL ATTENUATOR switch to the 50 volts/cm position.

(    )         Connect a test lead to the vertical input.

(    )         Connect the same test lead to the 150 VDC FOR CAL output [front panel].

(    )         Set the vertical AC-DC switch to the DC position.

(    )         Adjust the VERTICAL GAIN control (R7) to full counter-clockwise.

(    )         Adjust the VERTICAL CENTERING control (R13) until the trace is centered on the graticule grid.

(    )         Adjust the VERTICAL GAIN control (R7) clockwise until the trace moves up 3 cm.

(    )         Re-install the Vertical Gain knob with the pointer indexed on the red dot on the front panel [to the right of the control].

(    )         Adjust the VERTICAL GAIN control (R7) to full counter-clockwise.

(    )         Set the VERTICAL ATTENUATOR switch to the 20 volts/cm position.

(    )         Adjust the VERTICAL CENTERING control (R13) until the trace is on the bottom base line of the graticule grid.

(    )         Adjust the VERTICAL GAIN control (R7) clockwise to the red dot.

(    )         The trace should move upward approximately 7-1/2 cm.

(    )         Adjust the INTENSITY controls (R71) to full counter-clockwise.

(    )         Adjust the H. V. ADJUST control (R69) [bottom chassis plate] until the trace disappears.

(    )         Disconnect the test lead from both the vertical input and the 150 VDC CAL output.

* * * * * * *

Sweep Calibration

(    )         Set the SWEEP FREQUENCY switch to the .2 ms/cm position.

(    )         Adjust the VARIABLE MULTIPLIER control (R38) to the 1 position.

(    )         Connect the Frequency Counter input and the square wave output of the Audio Generator together using RG59 coax cables and a BNC T-adapter.

(    )         Adjust the Audio Generator for a frequency of 1 kHz.

(    )         Connect the T-adapter to the vertical input using a UHF-BNC adapter.

(    )         Adjust the SWEEP CALIBRATION control (R41) [bottom chassis plate] until 2 complete cycles are present on the display.

(    )         Adjust the VARIABLE MULTIPLIER control (R38) to the 10 position.

(    )         Adjust the SWEEP RANGE control (R40) [bottom chassis plate] until 20 complete cycles are present on the display.

(    )         Set the SWEEP FREQUENCY switch to the .1 ms/cm position.

(    )         Adjust the Audio Generator for a frequency of 50 kHz.

(    )         Adjust the HIGH FREQUENCY SWEEP ADJUST trimmer (C26) [behind front panel] until 2 complete cycles are present on the display.

(    )         Disconnect the Audio Generator only from the T-adapter.

* * * * * * *

Vertical High Frequency Compensation

Refer to bottom photo

Operation Manual, page 16

(    )         Set the VERTICAL ATTENUATOR switch to the .1 volts/cm position.

(    )         Connect a RG59 coax cable from the 1 MHz square wave generator to the T-adapter.

(    )         Adjust the VERTICAL HIGH FREQUENCY trimmer (C102) [left side of chassis] for a sharp squared off corner trace.

(    )         Disconnect the T-adapter and UHF-BNC adapter from the vertical input.

* * * * * * *

Vertical Attenuator Trimmers

Refer to bottom photo

Operation Manual, page 16

(    )         Set the VERTICAL ATTENUATOR switch to the 1 volt/cm position.

(    )         Set the SWEEP FREQUENCY switch to the .2 ms/cm position.

(    )         Adjust the STABILITY control (R35) to full clockwise.

(    )         Connect a test lead to the vertical input.

(    )         Connect the same test lead to the center lug of the HORIZONTAL GAIN control (R51).

(    )         Adjust both the HORIZONTAL GAIN control (R51) and the VERTICAL GAIN control (R7) until a diagonal trace is displayed. [Refer to diagram J, Operation Manual, page 20]

(    )         Adjust input trimmer (C2) [nearest front panel] until the straightest diagonal trace is displayed.

(    )         Turn the PHASING control (R42) counter-clockwise to the AC OFF position.

(    )         Disconnect the test lead from the HORIZONTAL GAIN control.

(    )         Connect the same test lead to the 12BH7 tube socket pin 1 (V-16).

(    )         Turn the PHASING control (R42) counter-clockwise to the ON position.

               (Allow the instrument to warm up for 5 minutes)

(    )         Adjust both the HORIZONTAL GAIN control (R51) and the VERTICAL GAIN control (R7) until a diagonal trace is displayed. [Refer to diagram K, Operation Manual, page 20]

(    )         Adjust input trimmer (C3) [next to trimmer C2] until the straightest diagonal trace is displayed.

(    )         Turn the PHASING control (R42) counter-clockwise to the AC OFF position.

(    )         Disconnect all test leads from the instrument.

 (    )        Disconnect the line cord from the AC power line.

 (    )        Calibration procedure is complete.