Heathkit Model IT-11

Capacitor Checker

Calibration Procedure

Ancillary Equipment Needed

VTVM

200-ohm 1% resistor

100K 5% resistor (brown-black-yellow-gold)

1.5M 5% resistor (brown-green-green-gold)

· Mount each resistor on a dual banana plug to use as a calibration standard.

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EYE TUBE ALIGNMENT

(    )         Set the POWER switch to the ON position. Allow the tubes to come up to operating temperature.

(    )         Set the BRIDGE – LEAKAGE switch to the BRIDGE position.

(    )         Adjust the BALANCE control for the minimum eye tube opening.

(    )         Adjust the eye tube in its mounting clip until the eye opening is vertical.

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INITIAL TESTS

(    )         Set the BRIDGE - LEAKAGE switch to the BRIDGE position.

(    )         Set the GEN. switch to the INT position.

(    )         Set the TYPE switch to any position.

(    )         Set the VOLTAGE switch to the 3 position.

(    )         Set the POWER FACTOR maximum counter-clockwise.

(    )         Set the RANGE switch to the ** position.

· ** For RANGE switch positions R X1 through C X1, the eye tube should be closed with the BALANCE control in any position except at maximum clockwise.  The eye should only open with the BALANCE control at maximum clockwise with your finger touching the negative TEST terminal.  The eye tube should tend to close when the RANGE switch is in positions R X100 through C X.01.

(    )         Set the RANGE switch to the C EXT. SCALE position.

· The eye tube should be closed regardless of the BALANCE control position.

(    )         Set the RANGE switch to the EXT. STD position.

· The eye tube should be open regardless of the BALANCE control position.

(    )         Touch the negative TEST terminal or the red EXT. STD terminal.  Eye tube should close.

(    )         Set the GEN. switch to the EXT. position.

· The eye tube should remain open regardless of the RANGE switch or BALANCE control position.

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VOLTAGE TEST

(    )         Connect a VTVM to the TEST terminals.

(    )         Set the BRIDGE – LEAKAGE switch to the LEAKAGE position.

(    )         Set the TYPE switch to the ELECTROLYTIC position.

(    )         Turn the VOLTAGE switch from the 3 position through the 16 positions to the 600 position, and observe the voltage reading at each position.  The VTVM reading should be close to the scale indications.

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BRIDGE CALIBRATION

(    )         Connect a 200-ohm 1% precision resistor across the TEST terminals.

(    )         Set the RANGE switch to the R X1 position.

(    )         Set the BRIDGE - LEAKAGE switch to the BRIDGE position.

(    )         Set the GEN. switch to the INT position.

(    )         Adjust the BALANCE control for the maximum eye tube opening.

(    )         Loosen the BALANCE knob setscrew and position the BALANCE pointer vertically down to the 1 position on the outside scale and retighten the setscrew.

(    )         Disconnect the 200-ohm1% resistor from the TEST terminals.

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LEAKAGE CALIBRATION

Calibration without a Milliamp Meter

(    )         Set the A.C. switch to the ON position.

(    )         Set the BRIDGE – LEAKAGE switch to the DISSCHARGE position.

(    )         Connect a 100K 5% (brown-black-yellow-gold) resistor across the TEST terminals.

(    )         Set the VOLTAGE switch to the 300 V position.

(    )         Set the TYPE switch to the ELECTROLYTIC position.

(    )         Set the BRIDGE - LEAKAGE switch to the LEAKAGE position.

(    )         Adjust the top control (AD) [on chassis] until the eye tube is “just closed”

(    )         Set the BRIDGE – LEAKAGE switch to the DISSCHARGE position.

(    )         Disconnect the resistor from the TEST terminals.

(    )         Connect a 1.5meg 5% (brown-green-green-gold) resistor across the TEST terminals.

(    )         Set the VOLTAGE switch to the 25 position.

(    )         Set the TYPE switch to the MIN.’LYTIC position.

(    )         Set the BRIDGE – LEAKAGE switch to the LEAKAGE position.

(    )         Adjust the bottom control (AB) [on chassis] until the eye tube is “just closed”

(    )         Set the VOLTAGE switch to the 3 position.

(    )         Set the TYPE switch to the PAPER position.

(    )         Set the BRIDGE – LEAKAGE switch to the LEAKAGE position.

(    )         Adjust the center control (AC) [on chassis] until the eye tube is “just closed”

(    )         Set the BRIDGE – LEAKAGE switch to the DISCHARGE position.

(    )         Disconnect the 1.5M 5% resistor from the TEST terminals.

Calibration with a Milliamp Meter

(    )         Set the A.C. switch to the ON position.  Allow the tubes to come up to operating temperature.

(    )         Set the BRIDGE – LEAKAGE switch to the DISCHARGE position.

(    )         Connect a 2-meg linear potentiometer in series with a 5 milliamp meter across the TEST terminals.

(    )         Set the VOLTAGE switch to the 50 position.

(    )         Set the TYPE switch to the ELECTROLYTIC position.

(    )         Set the BRIDGE – LEAKAGE switch to LEAKAGE.

(    )         Adjust the 2-meg control until the meter reads 2 milliamps.

(    )         Adjust the top control (AD) [on chassis] until the eye tube is “just closed”

(    )         Set the BRIDGE – LEAKAGE switch to the DISCHARGE position.

(    )         Disconnect the 5 milliamp meter and replace it with a 20 micro-amp meter.  Keep the 2-meg control connected in series with the new meter, and reconnect the unit across the TEST terminals.

(    )         Set the TYPE switch to the MIN.’LYTIC position.

(    )         Reduce the VOLTAGE switch setting.

(    )         Set the BRIDGE – LEAKAGE switch to the LEAKAGE position.

(    )         Adjust the 2-meg control until the meter reads 15 micro-amps.

(    )         Adjust the bottom control (AB) [on chassis] until the eye tube is “just closed”

(    )         Set the BRIDGE – LEAKAGE switch to the DISCHARGE position.

(    )         Set the TYPE switch to the PAPER position.

(    )         Set the BRIDGE – LEAKAGE switch to the LEAKAGE position.

(    )         If necessary, reduce the VOLTAGE switch setting, and increase the 2-meg control until the meter reads 2 micro-amps.

(    )         Adjust the center control (AC) [on chassis] until the eye tube is “just closed”

(    )         Set the BRIDGE – LEAKAGE switch to the DISCHARGE position.

(    )         Disconnect the 2M potentiometer and meter from the TEST terminals.

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LEAKAGE REFERENCE CHECK

· Due to component tolerances and line voltage variations, it is usually not possible to draw 2 ma from the instruments power supply on the 25 volt setting of the VOLTAGE switch.  To determine the degree of eye tube closure under shot circuit conditions.

(    )         Set the VOLTAGE switch to the 25 position.

(    )         Set the BRIDGE – LEAKAGE switch to the LEAKAGE position.

(    )         Set the TYPE switch to the ELECTROLYTIC position.

(    )         Momentarily short the TEST terminals with a screwdriver and observe the eye tube.  The size of the opening remaining should be mentally remembered as an indication of short circuit condition on the 25 V setting only.

(    )         Set the VOLTAGE switch to the 50 position.

(    )         Momentarily short the TEST terminals with a screwdriver and observe the eye tube.  The eye should be completely closed.

· A completely shorted capacitor will be detected during the value test (Bridge Circuit).  It is not recommended that the leakage test be performed on a known shorted capacitor, since possible damage to the power supply could occur.

(    )         Set the BRIDGE – LEAKAGE switch to the DISCHARGE position.

(    )         Set the TYPE switch to the MIN.’LYTIC position.

(    )         Set the VOLTAGE switch to the 3 position.

(    )         Set the POWER switch to the OFF position.

(    )         Calibration procedure is complete.