Bell System Practices 1A Installation And Maintenance page 4

SECTION 512-610-200CA
• See that key buttons are free and returned
to their unoperated positions after being
depressed fully.
• Have customer take the necessafy action
to restore power in case of power-off
condition.
• See that v.olume-control knob is free to
rotate over its entire range of operation.
• Check contacts that make on operating the
ON and OFF keys for perceptible follow.
The power cord should always be re-
moved from the powe1' outlet while
work is being done on 'control ~tnit.
• Adjust springs with 363 tool.
• Clean contacts with 265C tool, using clean
burnisher blade.
• In addition to, the above requirements,
check those in Para. 3.06.
5. LOUDSPEAKER 758A
5.01
When performing maintenance on a 758A
loudspeaker, proceed as follows:
• Replace chipped or cracked loudspeaker
housing.
• Replace any bent or missing grids.
• Replace any soiled or missing friction pads.
• Clean loudspeaker housing with a soft,
water-dampened cloth.
• If trouble develops in speaker itself,
replace complete 758A loudspeaker unit.
6. CONTROL UNITS KS-14964, LIST 2
6.01
For maintenance on control unit KS-14964,
List 2, proceed as follows:
• Check to see that the power cord of the
control unit is in the commercial power
outlet.'
• Press the ON button in the 592-type set or
the 656A transmitter.
If
the pilot lamp
does not light, and no sound comes from
the 758A loudspeaker, check the power
outlet with a neon voltage tester or
equivalent.
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• When commercial power is entering the
control unit, and amplification seems to be
deficient in either receiver or transmitter
circuit or both, replace the KS-14990 am-
plifier unit with one known to be service-
able.
• If changing the amplifier clears the trouble,
interchange the tubes, one at a time, from
good amplifier to defective amplifier.
Orient them so that the red mark on the
tube base faces both the top of the card and
the dot near the top end of the socket. If
this does not clear the trouble, it can be
assumed that trouble is internal in the KS-
14990 amplifier. Leave serviceable ampli-
fier in place and return defective amplifier
according to local instructions.
Note:
Do not change amplifier gain controls.
• If
trouble still persists, exchange complete
unit with a KS-14964, List 2 unit.
6.02
Fluorescent lights, transformers, motors,
or other similar apparatus on the cus-
tomer's premises may cause an inductive noise in
the loudspeaker. Grounding the amplifier' chassis
may eliminate this noise. In certain areas local
ordinances may not permit grounding. Be guided
by local instructions.
7. RADIO INTERFERENCE
7.01
Where radio interference is experienced in
the telephone set, a suppressor may be in-
stalled. See section entitled Radio Signal Sup-
pression in Telephone Sets.