Heathkit Model IO-12

Laboratory 5-inch 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 chassis and panel internal adjustments.


Ancillary Equipment Needed

 

Audio Signal Generator

Frequency Counter


* * * * * * *

FRONT PANEL INITIAL ADJUSTUP

 

(    )         Adjust the INTEN control (R78) to the full counter-clockwise to the OFF position.

 

(    )         Adjust the FOCUS control (R80) to the center of rotation.

 

(    )         Adjust the VERT POS control (R18) to the center of rotation.

 

(    )         Adjust the HOR POS control (R55) to the center of rotation.

 

(    )         Adjust the VERT GAIN control (R8) to the full counter-clockwise position.

 

(    )         Set the HOR / FREQ SELECTOR switch to the EXT INPUT position.

 

(    )         Adjust the HOR GAIN control (R52) to the full counter-clockwise position.

 

(    )         Set the VERT INPUT switch to the X100 position.

 

(    )         Adjust the FREQ VERNIER control (R48) to the 50 position.

 

(    )         Adjust the PHASE control (R72) to the center of rotation.

 

(    )         Adjust the EXT SYNC AMPLITUDE control (R31) to the full counter-clockwise position.

 

(    )         Set the SYNC SELECTOR switch to the EXT position.

 

(    )         Adjust the SPOT SHAPE (R75) [right side of chassis] to the center of rotation.

 

TRACE ADJUSTMENT

 

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

 

(    )         Adjust the INTEN control (R78) clockwise until the switch clicks to the ON position.

               (Allow the instrument to warm up for five minutes.)

 

(    )         Adjust the INTEN control (R78) clockwise until a spot just appears on the display.

 

(    )         Adjust the FOCUS control (R80) to reduce the size of the spot to a minimum.

 

♦ CAUTION: DO NOT PERMIT A HIGH INTENSITY SPOT TO REMAIN STATIONARY ON THE DISPLAY FOR ANY LENGTH OF TIME. THIS MAY DESTROY THE FLUORESCENT MATERIAL ON THE TUBE AND LEAVE A DARK SPOT.

 

(    )         Adjust the HOR POS control (R55) from full counter-clockwise to the full clockwise position.

               (The spot should move horizontally across the display.)

 

(    )         Adjust the HOR POS control (R55) to the center of rotation.

 

(    )         Adjust the VERT POS control (R18) from full counter-clockwise to the full clockwise position.

               (The spot should move vertically across the display.)

 

(    )         Adjust the VERT POS control (R18) to the center of rotation.

 

(    )         Adjust the INTEN control (R78) and the FOCUS control (R80) to reduce the size of the spot to a minimum.

 

(    )1        Adjust the SPOT SHAPE (R75) [right side of chassis] to make the spot as round as possible.

 

(    )2        Adjust the INTEN control (R78) and the FOCUS control (R80) to reduce the size of the spot to a minimum.

 

(    )         Repeat the above two steps * for the best spot size and shape.

 

CATHODE RAY TUBE ALIGNMENT

See Pictorial 9

Construction Manual, page 26

 

♦ This adjustment only needs to be performed if the trace is not horizontal across the display.

 

(    )         Adjust the INTEN control (R78) to the full counter-clockwise to the OFF position.

 

(    )         Loosen the mounting brackets at the neck of the CRT.

 

(    )         Adjust the INTEN control (R78) clockwise until the switch clicks to the ON position.

               (Allow the instrument to warm up for five minutes.)

 

(    )         Adjust the INTEN control (R78) clockwise until a spot just appears on the display.

 

(    )         Connect a test lead to the 1-V P-P terminal.

 

(    )         Connect this same test lead to the HOR INPUT terminal.

 

(    )         Adjust the HOR GAIN control (R52) to the full clockwise position.

 

(    )         Note the trace position on the display.

 

(    )1        Adjust the INTEN control (R78) to the full counter-clockwise to the OFF position.

 

(    )2        Rotate the CRT until the trace should be level.

 

(    )3        Adjust the INTEN control (R78) clockwise until the switch clicks to the ON position.

               (Allow the instrument to warm up for five minutes.)

 

(    )4        Adjust the INTEN control (R78) clockwise until a trace just appears on the display.

 

(    )         Repeat the above four steps * until the trace is level.

 

(    )         Adjust the INTEN control (R78) to the full counter-clockwise to the OFF position.

 

(    )         Tighten the mounting brackets at the neck of the CRT.

 

(    )         Adjust the INTEN control (R78) clockwise until the switch clicks to the ON position.

               (Allow the instrument to warm up for five minutes.)

 

(    )         Adjust the INTEN control (R78) clockwise until a trace just appears on the display.

 

(    )         Disconnect the test lead from the HOR INPUT terminal.

 

(    )         Connect this same test lead to the VERT INPUT terminal.

 

(    )         Adjust the VERT GAIN control (R8) from full counter-clockwise to the full clockwise position.

 

(    )         Note that the trace is now vertical and controlled by the VERT GAIN control (R8).

 

(    )         Set the VERT INPUT switch to the X10 position.

 

(    )         Adjust the VERT GAIN control (R8) from full counter-clockwise to the full clockwise position.

 

(    )         Note that the trace is now full screen at a lower setting of the VERT GAIN control (R8).

 

SWEEP GENERATOR OPERATION

 

(    )         Set the SYNC SELECTOR switch to the +INT position.

 

(    )         Adjust the HOR GAIN control (R52) to the 30 position.

 

(    )         Adjust the VERT GAIN control (R8) to the full clockwise position.

 

(    )         Set the HOR / FREQ SELECTOR switch to the dot between the 10 and 100 position.

 

(    )         Adjust the FREQ VERNIER control (R48) for four complete sine waves.

               [See Figure 1, Construction Manual, page 31]

 

·         This check indicates that the sweep generator is operating normally at a frequency of 60/4 or 15 Hz.

 

·         The breaks in the trace are caused by the transformer fields. They will not be present with external signals.

 

(    )         Disconnect the test lead from the 1-V P-P terminal.

 

VERTICAL INPUT TRIMMER ADJUSTMENT

 

(    )         Adjust the INTEN control (R78) to the full counter-clockwise to the OFF position.

 

(    )         Connect this same test lead to the HOR INPUT terminal.

 

(    )         Adjust the INTEN control (R78) clockwise until the switch clicks to the ON position.

               (Allow the instrument to warm up for five minutes.)

 

(    )         Adjust the INTEN control (R78) clockwise until a trace just appears on the display.

 

(    )         Set the HOR / FREQ SELECTOR switch to the dot between the 1000 and 10 kHz position.

 

(    )         Adjust the FREQ VERNIER control (R48) to the full counter-clockwise position.

 

(    )         Adjust the INTEN control (R78) clockwise until the switch clicks to the ON position.

               (Allow the instrument to warm up for five minutes.)

 

(    )         Adjust the INTEN control (R78) clockwise until a trace just appears on the display.

 

(    )         Adjust both the HOR GAIN control (R52) and the VERT GAIN control (R8) until the diagonal trace is about 2 inches long. [See Figure 2A or 2B, Construction Manual, page 31]

 

(    )         Set the VERT INPUT switch to the X10 position.

 

(    )         Adjust the front trimmer (C1) [left front chassis support] until any trace distortion disappears [Figure 2C].

 

(    )         Set the VERT INPUT switch to the X100 position.

 

(    )         Adjust the rear trimmer (C4) [left front chassis support] until any trace distortion disappears [Figure 2C].

 

(    )         Disconnect the test lead from the VERT INPUT terminal.

 

(    )         Disconnect this same test lead from the HOR INPUT terminal.

 

(    )         Adjust the INTEN control (R78) to the full counter-clockwise to the OFF position.

 

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

 

(    )         Assemble the instrument into its case.

 

ADJUSTING THE PRESET CONTROLS

 

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

 

(    )         Adjust the INTEN control (R78) clockwise until the switch clicks to the ON position.

               (Allow the instrument to warm up for five minutes.)

 

(    )         Adjust the INTEN control (R78) clockwise until a trace just appears on the display.

 

PRESET 1 Adjustment

(10 Hz to 100 Hz)

 

(    )         Connect the Audio Generator output to the Frequency Counter’s input

 

(    )         Adjust the Audio Generator to the desired frequency.

 

(    )         Disconnect the Frequency Counter.

 

(    )         Connect the Audio Generator to the VERT INPUT terminal.

 

(    )1        Set the SYNC SELECTOR switch to the EXT position.

 

(    )2        Set the HOR / FREQ SELECTOR switch to the PRESET 1 position.

 

(    )3        Adjust the VERT GAIN control (R8) for a 1 inch trace.

 

(    )4        Adjust PRESET 1 ADJUST control (R45) [marked hole on front panel] until two complete cycles appear on the display.

 

(    )5        Set the SYNC SELECTOR switch to the +INT position.

 

(    )         Repeat the above five steps * if the trace is not locked.

 

(    )         Disconnect the Audio Generator.

 

PRESET 2 Adjustment

(1000 Hz to 10 kHz)

 

(    )         Connect the Audio Generator output to the Frequency Counter’s input

 

(    )         Adjust the Audio Generator to the desired frequency.

 

(    )         Disconnect the Frequency Counter.

 

(    )         Connect the Audio Generator to the VERT INPUT terminal.

 

(    )1        Set the SYNC SELECTOR switch to the EXT position.

 

(    )2        Set the HOR / FREQ SELECTOR switch to the PRESET 2 position.

 

(    )3        Adjust the VERT GAIN control (R8) for a 1 inch trace.

 

(    )4        Adjust PRESET 2 ADJUST control (R46) [marked hole on front panel] until two complete cycles appear on the display.

 

(    )5        Set the SYNC SELECTOR switch to the +INT position.

 

(    )         Repeat the above five steps * if the trace is not locked.

 

(    )         Disconnect the Audio Generator.

 

(    )         Adjust the INTEN control (R78) to the full counter-clockwise to the OFF position.

 

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

 

(    )         Calibration procedure is complete.