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Section 4—485/R485 Service
MAINTENANCE
Introduction
This section of the manual contains maintenance infor
mation for use in preventive maintenance, corrective
maintenance, or troubleshooting of the 485.
Cover Removal
W A R N I N G
Dangerous potentials exist a t several p o in ts through
o u t this instrum ent. When the instrum ent is operated
w ith the cover removed, do n o t touch exposed
connections o r components. Some transistors have
voltage present on their cases. Disconnect power
before cleaning the instrum ent o r replacing parts.
1. Move handle away from front of instrument and snap
front plastic cover in place.
2. Place instrument front panel down on working
surface and remove the rear feet (four screws).
3. Work the small, blue rear panel rim away from the
back of the instrument. It may stick in place, due to EMI
finger stock. The edge opposite the BNC connectors must
tip up first in order to clear the BNC connectors.
4. Back the Accessory pouches large retaining screw out
so that its tip w ill clear the back panel for removal of the
wrap-around cover, and slip the cover up and o ff the
instrument.
Reinstalling the Cover
1. Orient the instrument face down (with the plastic
knob cover in place) on a working surface.
2. Slide the wrap-around cover on using care to avoid
pinching any cables. Make sure that the cover edge is
inserted into the EMI gasket groove around the full
periphery.
3. Work the blue rear panel rim into place at the rear
end. Slip the edge over the BNC connectors first and press
the ring down around the EMI finger stock.
4. Set the feet and screws in place and recheck that the
front end edge of the cover is iin the front panel EMI gasket
groove. Tighten the four screws of the rear feet to a snug
fit. Don't over-tighten these screws. Retighten the pouch
retaining screw.
The cover protects this instrument from dust in the
interior and also provides protection to personnel from the
operating potentials present. In addition, it reduces the EMI
radiation from the instrument or EMI interference to the
display due to other equipment.
W A R N I N G
Extrem e caution must be used when troubleshooting
in the Power Supply, due to the line voltage and the
high potentials present. Refer to the discussion
e n title d Troubleshooting the Power Supply for
troubleshooting inform ation.
P R E V E N T IV E M A IN TE N A N C E
General
Preventive maintenance consists of cleaning, visual
inspection, lubrication, etc. Preventive maintenance per
formed on a regular basis may prevent instrument break
down and w ill improve the reliability of this instrument.
The severity of the environment to which the 485 is
subjected determines the frequency of maintenance. A
convenient time to perform preventive maintenance is
preceding recalibration of the instrument.
Cleaning
General. The 485 should be cleaned as often as operating
conditions require. Accumulation of d irt in the instrument
can cause overheating and component breakdown. Dirt on
components acts as an insulating blanket and prevents
efficient heat dissipation. It also provides an electrical
conduction path which may result in instrument failure.
The cover provides protection against dust in the interior of
the instrument. Operation w ithout the cover in place
necessitates more frequent cleaning.
^
C A U T I O N I
A v o id the use o f chemical cleaning agents which
m ight damage the plastics used in this instrument.
A vo id chemicals which contain benzene, toluene,
xylene, acetone o r sim ilar solvents. Recommended
cleaning agent is isopropyl alcohol.
Switch Contacts. Most of the switching in the 485 is
accomplished with circuit-board mounted, cam-actuated
contacts. Care must be exercised to preserve the high-
frequency characteristics of these switches. Seldom is
switch maintenance necessary, but if it is required, observe
the following precautions.
REV. C. SEPT. 1974
4-1
Summary of Contents for 485
Page 3: ...485 R485 rviice T h 5 0 Oscil oscope ...
Page 74: ...Rackmounting 485 R485 Service 6 6 ...
Page 128: ...485 R485 Service MAR 1979 5 m V B A L ADJ ...
Page 152: ... 0 iT s i ...
Page 164: ...2S2 n eKn s e s 5 4 85 Os c illo sc o p e REV F A U S 1 9 7 7 I 1 9 3 5B POWER SUPPLY 773 ...
Page 178: ......
Page 179: ...485 R485 OSCILLOSCOPE REV D MAR 1977 ...
Page 184: ...REV C MAR 1976 485 R485 OSCILLOSCOPE ...
Page 197: ......