Maintenance

Exterior

INSPECTION. Inspect the external portions of the instrument for damage, wear, and missing parts; use Table 6-2 as a guide. Instruments that appear to have been dropped or otherwise abused should be checked thoroughly to verify correct operation and performance. Deficiencies found that could cause personal injury or could lead to further damage to the instrument should be repaired immediately.

To prevent getting moisture inside the instrument during external cleaning, use only enough liquid to dampen the doth or applicator.

CLEANING. Loose dust on the outside of the instrument can be removed with a soft cloth or small soft-bristle brush. The brush is particularly useful for dislodging dirt on and around the controls and connectors. Dirt that remains can be removed with a soft cloth dampened in a mild detergent-and-water solution. Do not use abrasive cleaners. Clean the light filter and the crt face with a soft lint-free cloth dampened with either denatured alcohol or a mild detergent-and-water solution.

Interior

To gain access to internal portions of the instrument for inspection and cleaning, refer to the "Removal and Replacement Instructions" in the "Corrective Maintenance" part of this section.

INSPECTION. Inspect the internal portions of the instrument for damage and wear, using Table 6-3 as a guide. Deficiencies found should be repaired immediately. The corrective procedure for most visible defects is obvious; however, particular care must be taken if heat-damaged components are found. Overheating usually indicates other trouble in the instrument; therefore, it is important that the cause of overheating be corrected to prevent recurrence of the damage.

Table 6-2 External Inspection Checklist

Item

Inspect For

Repair Action

Cabinet and Front Panel

Cracks, scratches, deformations, and damaged hardware or gaskets.

Touch up paint scratches and replace defective parts.

Front-panel Controls

Missing, damaged, or loose knobs, buttons, and controls.

Repair or replace missing or defective items.

Connectors

Broken shells, cracked insulation, and deformed contacts. Dirt in connectors.

Replace defective parts. Clean or wash out dirt.

Carrying Handle

Correct operation.

Replace defective parts.

Accessories

Missing items or parts of items, bent pins, broken or frayed cables, and damaged connectors.

Replace damaged or missing items, frayed cables, and defective parts.

Table 6-3 Internal Inspection Checklist

Item

Inspect For

Repair Action

Circuit Boards

Loose, broken, or corroded solder connections. Burned circuit boards. Burned, broken, or cracked circuit-run plating.

Clean solder corrosion with an eraser and flush with isopropyl alcohol. Resolder defective connections. Determine cause of burned items and repair. Repair defective circuit runs.

Resistors

Burned, cracked, broken, or blistered.

Replace defective resistors. Check for cause of burned component and repair as necessary.

Solder Connections

Cold solder or rosin joints.

Resolder joint and clean with isopropyl alcohol.

Capacitors

Damaged or leaking cases. Corroded solder on leads or terminals.

Replace defective capacitors. Clean solder connections and flush with isopropyl alcohol.

Wiring and Cables

Loose plugs or connectors. Burned, broken, or frayed wiring.

Firmly seat connectors. Repair or replace defective wires or cables.

Chassis

Dents, deformations, and damaged hardware.

Straighten, repair, or replace defective hardware.

If any electrical component is replaced, conduct a Performance Check of the affected circuit and of other closely related circuits (see Section 4). If repair or replacement work is done on any of the power supplies, conduct a complete Performance Check and, if so indicated, an instrument readjustment (see Section 5).

To prevent damage from electrical arcing, ensure that circuit boards and components are dry before applying power to the instrument.

CLEANING. To clean the interior, blow off dust with dry, low-pressure air (approximately 9 psi). Remove any remaining dust with a soft brush or a cloth dampened with a solution of mild detergent and water. A cotton-tipped applicator is useful for cleaning in narrow spaces and on circuit boards.

If these methods do not remove all the dust or dirt, the instrument may be spray washed using a solution of 5% mild detergent and 95% water as follows:

1. Gain access to the parts to be cleaned (see "Removal and Replacement Instructions").

2. Spray wash dirty parts with the detergent-and-water solution; then use clean water to thoroughly rinse them.

3. Dry all parts with low-pressure air.

SWITCH CONTACTS. The Vertical and Horizontal attenuators in this instrument are circuit-board mounted rotary switches. When cleaning them, care must be exercised to preserve their high-frequency characteristics. Switch maintenance is seldom necessary, but if it is required, use the following cleaning method and observe the stated precaution.

Use only hot deionized or distilled water, 55°C (131°F), to dean a rotary switch in this instrument. Tap water contains impurities which are left as residuals after evaporation.

1. Spray hot water into the slots at the top of each switch housing while rotating the switch control knob. Spray only for approximately five seconds, using an atomizing spray device.

2. Dry both the switch and the circuit board on which it is mounted, using dry low-pressure air.

3. Bake the switch and the circuit board at 75°C (167°F) for 15 minutes to eliminate all moisture.

4. Spray a very small amount (only about a 1/2-second squirt) of a recommended lubricant, such as No Noise, into the slots at the top of the switch housing.

5. Rotate the switch control knob about 180° and again spray a very small amount of lubricant into each slot.

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