Tektronix 2215A, Instruction Manual

Page: 86 / 206

Maintenance— 2215A Service
CLEANING. To clean the interior, blow off dust with dry,
low-pressure air (approximately 9 psi). Remove any remain­
ing dust with a soft brush or a cloth dampened with a solu­
tion 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 VOLTS/DIV and the SEC/
DIV Switches are mounted circuit-boards within the instru­
ment. Care must be exercised to preserve the high-
frequency characteristics of these switches. Switch mainte­
nance is seldom necessary, but if it is required, observe the
following precautions.
1. The VOLTS/DIV switches contain cam-actuated
contacts.
M ost spray-type circuit coolants contain Freon 12 as
a propellant. Because many Freons adversely affect
switch contacts, do not use a spray-type coolants.
The only recommended circuit coolants fo r the volts-
division attenuators are dry ice (CO ) and isopropyl
alcohol.
a. Use only isopropyl alcohol as a cleaning solution, es­
pecially in the area of the vertical Attenuator circuit
board. Carbon-based solvents will damage the board
material.
b. Apply the alcohol with a small, camel-hair brush. Do
not use cotton-tipped applicators when cleaning
contacts.
2. The SEC/DIV switch is comprised of rotary-activated
contacts.
Use only hot deionized o r distilled water, 55° C
(131° F), to clean the timing switch in this instrument.
Tap water contains impurities which are left as residu­
als after evaporation.
a. 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.
b. Dry both the switch and the circuit board on which it is
mounted, using dry low-pressure air.
c. Bake the switch and the circuit board in an oven at
75 °C (167°F) for 15 minutes to eliminate all moisture.
d. 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.
e. Rotate the switch control knob about 180° and again
spray a very small amount of lubricant into each slot.
LUBRICATION
Most of the potentiometers used in this instrument are
permanently sealed and generally do not require periodic
lubrication. All switches, both rotary- and lever-type, are in­
stalled with proper lubrication applied where necessary and
will rarely require any additional lubrication. Therefore, a
regular periodic lubrication program for the instrument is not
recommended.
SEMICONDUCTOR CHECKS
Periodic checks of the transistors and other semiconduc­
tors in the oscilloscope are not recommended. The best
check of semi-conductor performance is actual operation in
the instrument.
PERIODIC READJUSTMENT
To ensure accurate measurements, check the perfor­
mance of this instrument after every 2000 hours of opera­
tion, or if used infrequently, once each year. In addition,
replacement of components may necessitate readjustment
of the affected circuits.
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