Heathkit Model IO-103
5-inch Triggered Sweep 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.
· Use an insulated or non-conducting screwdriver when making all front panel internal adjustments.
· If the oscilloscope is operating within its normal parameters, the skip down to the CALIBRATION section.
Ancillary Equipment Needed
Audio Signal Generator
Frequency Counter
VTVM
* * * * * * *
FRONT PANEL INITIAL SETUP
Refer to Figure 1-1
Construction Manual, page 80
Beam and Scale Controls
( ) Set the TRACE control (1) to the OFF (in) position.
( ) Adjust the TRACE control (1) to full clockwise.
( ) Adjust the GRADICULE control (21) to full clockwise.
( ) Adjust the FOCUS control (2) to the center of rotation.
( ) Adjust the ASTIG control (20) to the center of rotation.
Position Controls
( ) Adjust the VERTICAL POSITION control (5) to the center of rotation (dot).
( ) Set the HORIZONTAL POSITION switch (17) to the 1X (in) position.
( ) Adjust the HORIZONTAL POSITION control (17) to the center of rotation (dot).
Vertical Controls
( ) Set the VOLTS/CM switch (6) to the 20 position.
( ) Adjust the VARIABLE control (7) to full clockwise.
( ) Set the AC-GND-DC switch (8) to the GND position.
Time Base Controls
( ) Adjust the TRIGGER LEVEL control (11) to full counter-clockwise.
( ) Adjust the STABILITY control (10) to full counter-clockwise.
( ) Set the TIME/CM switch (16) to the EXT IN position.
( ) Adjust the HORIZONTAL GAIN control (15) to full counter-clockwise.
Trigger Controls
( ) Set the TRIGGER INT/EXT switch (4) to the INT position.
( ) Set the TRIGGER MODE AC/DC switch (3) to the AC position.
( ) Set the TRIGGER MODE +/- switch (19) to the + position.
( ) Set the TRIGGER MODE AUTO/NORM switch (18) to the AUTO position.
* * * * * * *
ATTENUATOR BOARD SETUP
[Front Panel]
Refer to Figure 2-1
Construction Manual, page 84
( ) Adjust the BAL control (R11) [right top] to the center of rotation.
( ) Adjust the POS ADJ control (R12 & R13) [right bottom] to the center of rotation.
( ) Adjust the CAL control (R4) [left top] to the center of rotation.
* * * * * * *
POWER SUPPLY BOARD SETUP
[Right side of chassis]
Refer to Figure 2-3
Construction Manual, page 84
( ) Adjust the CRT BIAS control (R402) to the center of rotation.
( ) Adjust the POSITION ADJUST control BB (R514) [main chassis] to the center of rotation.
* * * * * * *
SWEEP GENERATOR & HORIZONTAL AMPLIFIER BOARD SETUP
[Right side of chassis]
Refer to Figure 2-3
Construction Manual, page 84
( ) Adjust the SWEEP CAL control (R330) to the center of rotation.
( ) Adjust the FEEDBACK ADJUST control (R333) to the center of rotation.
( ) Adjust the LEVEL SET control (R308) to the center of rotation.
( ) Adjust the TRIGGER BALLANCE control (R315) to the center of rotation.
( ) Adjust the DC LEVEL control (R301) to the center of rotation.
( ) Adjust the DC BALANCE control (R202) to the center of rotation.
( ) Adjust the GAIN CAL control (R309) to the center of rotation.
( ) Adjust the HORIZONTAL 100 V ADJUST control (R204) to the center of rotation.
* * * * * * *
VERTICAL AMPLIFIER BOARD SETUP
[Underside of circuit board bracket]
Refer to Figure 2-2A
Construction Manual, page 84
( ) Adjust the VERT 100 V ADJUST control (R104) to full clockwise.
* * * * * * *
ADJUSTMENTS
Refer to Figure 1-1
Construction Manual, page 80
Controls that work together
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Trace X X X
Vertical Display X X X X X
Horizontal Input X X X X
Automatic Trigger X X X X X X X X
Normal Trigger X X X X X X X X X X
( ) Connect the line cord to the AC power source.
( ) Set the VTVM’s input switch to the DC+ position.
( ) Set the VTVM’s range switch to the 15-volts scale position.
( ) Connect the ground lead from the VTVM to the oscilloscope’s chassis.
( ) Set the TRACE control (1) to the ON (out) position.
(Allow the instrument to warm up for 5 minutes.)
( ) Adjust the GRADICULE control (21) to observe display lighting.
( ) Connect the VTVM’s test probe to the positive lead of capacitor C104.
[Refer to Figure 2-2B, page 84]
( ) Adjust the VERT 100 V ADJUST control (R104) [Figure 2-2B] counter-clockwise until a reading of +9 volts. [Refer to Figure 2-2A, page 84]
( ) Disconnect the test probe.
( ) Connect the test probe to the Source lead (S) of transistor Q1 on the Attenuator Board.
[Reference Figure 2-4, page 85 & PICTORIAL 4-1, page 34]
( ) Adjust the BAL control (R11) [front panel] until a reading of 0 volts.
[Refer to Figure 2-1, page 84]
♦ Reduce the VTVM’s range scale position as the voltage indication decreases.
* * * * * * *
Vertical Amplifier Position Adjustment
Refer to Figure 2-2
Construction Manual page 84
( ) Set the VTVM’s range switch to the 500-volts scale position.
( )1 Connect the test probe to the collector of transistor Q111.
( )2 Note the voltage indication.
( )3 Disconnect the test probe.
( )4 Connect the test probe to the collector of transistor Q112.
( )5 Note the voltage indication.
( )6 Adjust the POS ADJ control (R12 & R13) [front panel] until the two voltages are equal.
♦ One collector voltage will increase while the other one decreases.
( )7 Disconnect the test probe.
( ) Repeat the above seven steps* until both of the voltage readings are equal with no adjustment.
( ) Connect the test probe to the collector of either transistor Q111 or Q112.
( ) Adjust the VERT 100 V ADJUST control (R104) [Figure 2-2B] counter-clockwise until a reading of 100 volts.
( ) Set the VTVM’s range switch to the 150-volts scale position.
( ) Re-adjust the VERT 100 V ADJUST control (R104) until a reading of 100 volts.
( )* Repeat the seven step Vertical Amplifier Positioning adjustment outlined above.
( )* Re-adjust the VERT 100 V ADJUST control (R104) until a reading of 100 volts.
( ) Repeat the above two steps * until no changes are observed.
( ) Disconnect the test probe.
( ) Set the VTVM’s range switch to the 15-volts scale position.
( ) Connect the test probe to the positive lead of capacitor C104.
[Refer to Figure 2-2B, page 84]
( ) Re-adjust the VERT 100 V ADJUST control (R104) until a reading of +9 volts.
( ) Disconnect the test probe.
( ) Connect the test probe to the Source lead (S) of transistor Q201 [Sweep Gen and Horiz Amp board]. [Reference Figure 2-3, INSERT #2, page 84]
( ) Adjust the HORIZ DC BAL control (R202) until a reading of 0 volts.
♦ Reduce the VTVM’s range scale position as the voltage indication decreases.
( ) Disconnect the test probe.
* * * * * * *
Horizontal Amplifier Position Adjustment
Refer to Figure 2-3
Construction Manual page 84
( ) Set the VTVM’s range switch to the 500-volts scale position.
( )1 Connect the VTVM’s test probe to the collector of transistor Q213.
( )2 Note the voltage indication.
( )3 Disconnect the test probe.
( )4 Connect the VTVM’s test probe to the collector of transistor Q214.
( )5 Note the voltage indication.
( )6 Adjust the POSITION ADJUST control BB (R514) until the two voltages are equal.
♦ One collector voltage will increase while the other one decreases.
( )7 Disconnect the test probe.
( ) Repeat the above seven steps* until both of the voltage readings are equal with no adjustment.
( ) Connect the test probe to the collector of either transistor Q213 or Q214.
( ) Adjust the HORIZ 100 V ADJUST control (R204) counter-clockwise until a reading of 100 volts.
( ) Set the VTVM’s range switch to the 150-volts scale position.
( ) Re-adjust the HORIZ 100 V ADJUST control (R204) until a reading of 100 volts.
( )* Repeat the seven step Horizontal Amplifier Positioning adjustment outlined above.
( )* Re-adjust the HORIZ 100 V ADJUST control (R204) until a reading of 100 volts.
( ) Repeat the above two steps * until no changes are observed.
( ) Disconnect the test probe.
* * * * * * *
Trace Adjustment
( ) Adjust the CRT BIAS control (R402) [power supply board] until a spot appears on the face of the CRT.
( ) Adjust the TRACE control (1) [front panel] to full counter-clockwise.
( ) Re-adjust the CRT BIAS control (R402) until the CRT spot just disappears or the CRT BIAS control is at full counter-clockwise.
( ) Re-adjust the TRACE control (1) until the CRT spot reappears on the face of the CRT.
( ) Adjust both the FOCUS (2) and ASTIG (20) controls [front panel] for a minimum spot size.
* * * * * * *
CALIBRATION
Refer to Figure 1-1
Construction Manual, page 80
TRIGGER CIRCUITS
( ) Set the TIME/CM switch (6) to the 100 ms position.
( ) Adjust the VARIABLE (Time/CM) control (7) to full clockwise.
( ) Set the TRIGGER INT/EXT switch (4) to the INT position.
( ) Set the TRIGGER MODE AC/DC switch (3) to the AC position.
( ) Set the TRIGGER MODE +/- switch (19) to the + position.
( ) Set the TRIGGER MODE AUTO/NORM switch (18) to the AUTO position.
( ) Adjust the TRIGGER LEVEL control (11) to full counter-clockwise.
( ) Adjust the STABILITY control (10) to full counter-clockwise.
( ) Set the TRACE control (1) to the ON (out) position.
(Allow the instrument to warm up for 5 minutes.)
* * * * * * *
Refer to Figure 2-3
Construction Manual, page 84
( ) Connect the ground lead from the VTVM to the oscilloscope’s chassis.
( ) Set the VTVM’s range switch to the 5-volts scale position.
( ) Connect the VTVM’s test probe to TP1 (Source lead) of transistor Q302 [Sweep Gen and Horiz Amp board].
( ) Adjust the LEVEL SET control (R308) until a reading of 0 volts.
( ) Disconnect the test probe.
( ) Set the VTVM’s range switch to the 1.5-volts scale position.
( ) Connect the test probe to TP2 (Source lead) of transistor Q314 [Sweep Gen and Horiz Amp board].
( ) Adjust the FEEDBACK ADJUST control (R333) until a reading of 0.2 volts.
( ) Adjust the STABILITY control (10) until the trace appears on the face of the CRT.
( ) Adjust both the FOCUS (2) and ASTIG (20) controls [front panel] for a minimum spot size.
( ) Adjust the VERTICAL POSITION control (5) to the center of rotation (dot).
( ) Adjust the POSITION ADJUST control BB (R514) [main chassis] until the trace starts at the left vertical graticule line.
( ) 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 Set the TRACE control (1) to the OFF (in) 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 Set the TRACE control (1) to the ON (out) position.
· Repeat the above six steps * until the trace is parallel with the graticule lines.
( )** Allow the instrument to warm up for 5 minutes.
( ) Set the VOLTS/CM switch (6) to the .5 position.
( ) Adjust the VARIABLE control (7) to full clockwise.
( ) Set the AC-GND-DC switch (8) to the AC position.
( ) Set a Signal Generator for a sine wave output of 10 kHz.
( ) Connect either a pair of test leads or an RG59 coax cable to the generator’s output.
( ) Connect either the same test leads or coax cable to the VERT IN jack (9) of the oscilloscope.
( ) Adjust the generator’s output to display a 4 cm vertical deflection.
( ) Adjust the POSITION control (5) until the trace is centered on the screen.
( ) Adjust the TRIGGER BALANCE control (R315) until the trace is synchronized [refer to Figure 2-3].
( ) Set the TRIGGER MODE AUTO/NORM switch (18) to the NORM position.
( ) The CRT trace should disappear.
· If the trace disappears - skip the next five steps.
( )1 Set the TRIGGER MODE AUTO/NORM switch (18) to the AUTO position.
( )2 Adjust the STABILITY control (10) counter-clockwise slightly.
( )3 Re-adjust the TRIGGER BALANCE control (R315) until the trace is synchronized.
( )4 Set the TRIGGER MODE AUTO/NORM switch (18) to the NORM position.
( ) Repeat the above four steps * until the trace disappears.
( ) Adjust the TRIGGER LEVEL control (11) to lock in the signal trace.
( ) Note the position of the TRIGGER LEVEL control.
( ) Set the TRIGGER MODE +/- switch (19) to the – position.
( ) If the trace disappears, adjust the TRIGGER LEVEL control (11) until the trace appears.
( ) Note the position of the TRIGGER LEVEL control again.
( ) Adjust the TRIGGER LEVEL control (11) midway between the two noted positions.
( ) Re-adjust the TRIGGER BALANCE control (R315) until the trace is locked.
( )1 Switch the TRIGGER MODE +/- switch (19) between the + and – positions.
( )2 Note the trace start position.
( )3 Adjust the TRIGGER BALANCE control (R315) until the trace is locked [refer to Figure 2-3].
( ) Repeat the above three steps * until the trace starts at the same point at either TRIGGER MODE +/- switch position.
( ) Set the TRIGGER MODE AUTO/NORM switch (18) to the AUTO position.
( )1 Switch the TRIGGER MODE +/- switch (19) between the + and – positions.
( )2 Note the trace start position.
( )3 Adjust the LEVEL SET control (R308) until the trace is locked [refer to Figure 2-3].
( ) Repeat the above three steps * until the trace starts at the same point above and below the centerline at either TRIGGER MODE +/- switch position.
( ) Set the AC-GND-DC switch (8) to the DC position.
( )1 Switch the AC-GND-DC switch (8) between the AC and DC positions.
( )2 Note the trace start position.
( )3 Adjust the DC LEVEL control (R301) until the trace starts at the same point.
( ) Repeat the above three steps * until the trace starts at the same point at either the AC or DC switch position.
( ) Set the TRIGGER INT/EXT switch (4) to the INT position.
( ) Set the TRIGGER MODE AC/DC switch (3) to the AC position.
( ) Set the TRIGGER MODE +/- switch (19) to the + position.
( ) Set the TRIGGER MODE AUTO/NORM switch (18) to the NORN position.
( )1 Switch the TRIGGER MODE +/- switch (19) between the + and – positions.
( )2 Note the trace start position.
( )3 Adjust the TRIGGER LEVEL control (11) until the trace starts at the same point.
( ) Repeat the above three steps * until the trace starts at the same horizontal point on the centerline at either TRIGGER MODE +/- switch position.
( )* Remove the knob bushing from the STABILITY control (10) [Refer to Figure 1-1 foldout, page 80].
( )* Install the 1” pointer knob on the TRIGGER LEVEL control (11) bushing so the pointer is at the 12 o’clock position.
( )* Replace the knob bushing on the STABILITY control (10).
( )* Adjust the STABILITY control (10) shaft full counter-clockwise.
( )* Install a 3/4” pointer knob on the TRIGGER LEVEL control (11) bushing so the pointer is at the 7 o’clock position.
· The knob placement * should only be needed at the initial calibration.
* * * * * * *
SWEEP CALIBRATION
Refer to Figure 2-3
Construction Manual, page 84
( ) Set the TRIGGER INT/EXT switch (4) to the INT position.
( ) Set the TRIGGER MODE AC/DC switch (3) to the AC position.
( ) Set the TRIGGER MODE +/- switch (19) to the + position.
( ) Set the TRIGGER MODE AUTO/NORM switch (18) to the AUTO position.
( ) Adjust the STABILITY control (10) for a stable trace.
( ) Adjust the GAIN CAL control (R309) for an 8 cm horizontal trace.
( ) 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.
( ) Adjust the SWEEP CAL control (R330) for a display of 1-1/2 Hz.
♦ The accuracy of the oscilloscope’s time base is related to the accuracy of the 1 kHz square wave.
( ) Adjust the GAIN CAL control (R309) until 1 Hz is a 10 cm horizontal trace [refer to Figure 2-5, page 89].
· Viewing the 1 kHz square wave, the vertical traces may not be visible.
( ) Set the TIME/CM switch (16) to the 1 ms position.
( ) Set the HORIZONTAL POSITION switch (17) to the 2X (out) position.
( ) Adjust the 2X CALIBRATE control (R513) until 5 Hz are display.
[Front panel back, right side – refer to Figure 2-6A, page 89]
( ) Set the HORIZONTAL POSITION switch (17) to the 1X (in) position.
( ) Adjust the Audio Generator for a frequency of 100 kHz.
( ) Set the TIME/CM switch (16) to the 1 ms position.
( ) Trace may appear as A, B, or C [refer to Figure 2-7, page 84].
( ) Adjust trimmer capacitor C313 [Sweep & Trigger switch] until 1 Hz produces a 10 cm horizontal trace.
[Refer to Figure 2-8, page 84]
( ) Adjust the VERTICAL POSITION control (5) until the square wave appears as Figure 2-5.
· If the trace cannot be obtained, check the 1 kHz calibration performed above.
( ) Set the VOLTS/CM switch (6) to the .05 position.
( ) Adjust the Audio Generator signal for 4 cm of vertical deflection.
( ) Adjust the HORIZONTAL GAIN control (15) counter-clockwise to display several hertz.
* * * * * * *
VERTICAL COMPENSATION
Refer to Figure 2-2A
Construction Manual, page 84
( ) Adjust vertical trimmer capacitor (C106) [Vertical Amplifier board] until the trace appears as Figure 2-7A.
[Refer to Figure 2-2A, page 84]
( ) Adjust the Audio Generator for a frequency of 1 kHz.
( ) Set the VOLTS/CM switch (6) to the 2 position.
( ) Set the TIME/CM switch (16) to the 1 ms position.
( ) Adjust the HORIZONTAL GAIN control (15) counter-clockwise to display several hertz.
( ) Adjust the Audio Generator signal for 4 cm of vertical deflection.
* * * * * * *
Refer to Figure 2-1
Construction Manual, page 84
( ) Adjust the 2-volt vertical trimmer (C1) [front panel] until the trace appears [refer to Figure 2-7A].
( ) Set the VOLTS/CM switch (6) to the 5 position.
( ) Adjust the Audio Generator signal for 4 cm of vertical deflection.
( ) Adjust the 5-volt vertical trimmer (C5) [front panel] until the trace appears [refer to Figure 2-7A].
( ) Repeat all the above Vertical Compensation section steps until no further improvement is noted.
* * * * * * *
LOW CAPACITY PROBE COMPENSATION
* Without a Low Capacity Probe *
( ) Adjust the X 10 LOW CAPACITY TRIMMER (C2) [front panel] clockwise until just snug.
( ) Adjust the X 10 LOW CAPACITY TRIMMER counter-clockwise one-quarter turn.
( ) Skip down to the VERTICAL CALIBRATION section.
* With a Low Capacity Probe *
( ) Adjust the Audio Generator for a frequency of 1 kHz.
( ) Set the VOLTS/CM switch (6) to the .05 position.
( ) Adjust the Audio Generator signal for 4 cm of vertical deflection.
( ) Adjust the trimmer capacitor on the X 10 Low Capacity Probe until the trace appears as Figure 2-7A.
( ) Set the VOLTS/CM switch (6) to the .5 position.
( ) Adjust the Audio Generator signal for 4 cm of vertical deflection.
( ) Adjust the X 10 LOW CAPACITY TRIMMER (C2) [front panel] clockwise until the trace appears as Figure 2-7A.
* * * * * * *
VERTICAL CALIBRATION
( ) Disconnect the Audio Generator from the vertical input.
( ) Set the VOLTS/CM switch (6) to the .2 position.
( ) Set the TIME/CM switch (16) to the 1 ms position.
( ) Connect a test lead to the 1 V P-P output.
( ) Connect the same test lead to the vertical input.
( ) Set the AC-GND-DC switch (8) to the GND position.
( ) Adjust the HORIZONTAL GAIN control (15) until 5 Hz are displayed.
( ) Adjust the CAL control (R4) [front panel] for 5 cm of vertical deflection.
( ) Set the TRACE control (1) to the OFF (in) position.
( ) Disconnect all test leads from the instrument.
( ) Disconnect the line cord from the AC power line.
( ) Calibration procedure is complete.