Tektronix 502A

SECTION 4
MAINTENANCE
PREVENTIVE MAINTENANCE
Air Filter
Care must be taken to assure free ventilation of the
Type 502A inasmuch as some of the components are oper 
ated at dissipation levels such that excessive interior
temperatures will result without adequate air circulation.
To assure free passage of air the instrument must be placed
so that the air intake is not blocked and the filter must be
kept clean. Moreover, the side panels and bottom cover
must be in place for proper air circulation. Do not remove
the covers except during maintenance.
A washable filter is used at the air intake part of the
instrument. Under normal operating conditions the filter
should be inspected and cleaned if necessary every three
to four months. More frequent inspection is required when
the operating conditions are more severe.
The following cleaning procedure is suggested:
1. Flush loose dirt out of filter with a stream of hot water.
2. Prepare a hot water and mild soap or detergent
solution. Wash the filter as you would wash a sponge so
that the adhesive and dirt is loosened and floated off.
3. Rinse the filter and let it dry.
4. Dip or spray filter with fresh Filter Coat or Handi
Coater. These products are available from the local repre 
sentative of the Research Products Corporation and from
most air conditioner suppliers.
Fan Motor
The fan motor bearings are sealed and should not
require lubrication for the life of the motor.
Visual Inspection
You should visually inspect the entire oscilloscope every
few months for possible circuit defects. These defects may
include such things as loose or broken connections, damaged
binding posts, improperly seated tubes, scorched wires or
resistors, missing tube shields, or broken terminal strips.
For most visual troubles the remedy is apparent; however,
particular care must be taken when heat-damaged com 
ponents are detected. Overheating of parts is often the
result of other, less apparent, defects in the circuit. It is
essential that you determine the cause of overheating
before replacing heat-damaged parts in order to prevent
further damage.
Soldering and Ceramic Strips
Many of the components in your Tektronix instruments
are mounted on ceramic terminal strips. The notches in
these strips are lined with a silver alloy. Repeated use of
excessive heat, or use of ordinary tin-lead solder will break
the silver-to-ceramic bond. Occasional use of tin-lead solder
will not break the bond if excessive heat is not applied.
If you are responsible for the maintenance of a large
number of Tektronix instruments, or if you contemplate
frequent parts changes, we recommend that you keep on
hand a stock of solder containing about 3% silver. This
type of solder is used frequently in printed circuitry and
should be readily available from radio-supply houses. If
you prefer, you can order the solder directly from Tektronix
in one pound rolls. Order by Tektronix part number 251-514.
Fig. 4-1. Soldering iron tip properly shaped and tinned.
Because of the shape of the terminals on the ceramic
strips it is advisable to use a wedge-shaped tip on your
soldering iron when you are installing or removing parts
from the strips. Fig. 4-1 will show you the correct shape
for the tip of the soldering iron. Be sure to file smooth all
surfaces of the iron which will be tinned. This prevents
solder from building up on rough spots where it will
quickly oxidize.
When removing or replacing components mounted on the
ceramic strips you will find that satisfactory results are
obtained if you proceed in the manner outlined below.
4-1