Bell 300 Series Guide

BELLSYSTEMPRACTICES SECTIONC38.549
StationOperationsManual Issue3, March,1960
StationSets AT&TCoStandard
TELEPHONESETS- 300 SERIES
MAINTENANCE
1.00 INTRODUCTION head of each. If absent, install Shakeproof
No. 3099-08-01 (C) lock washer or replace
1.01 This section covers the requirements and baseplate mounting screwwith special head
adjusting procedures for the maintenance RHM screw, P-467742.
of telephone sets of types 302, 304, 306, 307, 309,
332, 334, 354, 356, and 357. • Replace defective parts when parts are
available; otherwise, replace set. The 426A
1.02 The 300-type sets for specific uses are cov- electron tubes can be used to replace the
ered in other C sections. 313A, 333A, 372A, and 405 electron tubes.
2.00 GENERAL • When a 101A gong attachment is to be
used on a set equipped with a ringer volume
2.01 Inspect exterior and interior of telephone control, the gongs shall be interchanged
set for loose, displaced, or broken parts and and the gong attachment placed on the stao
determine if any such defects are responsible for tionary gong.
the trouble condition, prior to proceeding with
routine maintenance. 2.02 Table A lists some of the troubles that may
• Check baseplate mounting screw to make occur, their probable causes, and correco
certain there is a lock washer under the tive measures.
TABLEA
Trouble ProbableCauses CorrectiveMeasures
Ringer disconnected or wired Connect correctly.
wrong in set
Open winding Replace ringer.
Metal particles in armature gap Remove particles with Scotch tape or ap-
Bell does not ring. proved equivalent.
No ground (party lines) Check ground circuit.
Open tube Short-circuit yellow and black tube lead.s
and, if ringer operates when ringing vol_-
age of correct polarity is applied, replace
tube.
Bell is too loud. Stroke limiting arm not prop- Reduce armature travel.
erly adjusted
Set on sound absorbent material Place set on hard surface or adjust stroke
Bell is not loud or stroke limiting arm not prop- limiting arm.
enough, erly adjusted
©AmericanTelephoneandTelegraphCompany,1960
PrintedinU. S.A. Page I

SECTIONC38.549
TABLEA (Cont)
Trouble ProbableCauses CorrectiveMeasures
Bell taps during dial- Incorrect wiring Check mounting cord and ringer connec-
ing, operating switch, Bias spring tension too low tions.
or when bridged
party is called. Move spring to higher tension notch. If
ringer still cross-rings, replace ringer. Do
not adjust bias spring.
Open in handset cord or at dial Replace cord or dial.
pulse contacts
Bell keeps ringing
when handset is Open induction coil or set wiring Replace coil.
removed. Line contacts on switch do not Clean contacts and check alignment.
close
Open handset cord or receiver Replace handset cord or receiver unit.
unit
Dial "off normal shunt" contacts Replace dial.
closed
Bell rings, no one on
line. Open induction coil or transmis- Replace parts.
sion capacitor
Switch receiver contacts do not Check contacts.
open
Open mounting or handset cords Replace cord.
Defective receiver unit Replace unit.
No dial tone, set Dial pulse contacts open or "off Replace dial.
seems dead. normal shunt" contacts closed
Open induction coil Replace coil.
Switch contacts do not operate Clean and adjust contacts.
Dial pulse contacts do not open Replace dial.
Dial tone cannot be
broken. Line reversed (tip party in No. 1 Reverse line.
XBR office)
Loud clicks occur Dial "off normal shunt" contacts Replace dial.
during dialing, do not close
Open or shorted receiver unit or Replace defective parts.
handset cord
Calling party cannot Dial "off normal shunt" contacts Replace dial
hear. closed
Open in induction coil Replace induction coil.
Switch receiver contacts do not Clean and adjust contacts.
Called party cannot open
hear. Defective transmitter or handset Replace transmitter or handset cord.
cord open
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ISS3, SECTIONC38.549
3.00 TYPES302, 304, 306, 307, 309, 354, 356,
AND 357
3.01 CONTACTS
• Clean contacts using a 265C tool with a
clean blade.
• The contacting surface of each contact shall _,_
fall wholly within the mating surface of
the opposing contact; if not, replace set.i_
3.02PLUNGERS _ INDERCUT
• If plungers bind or squeak, open set and
check for sticky plungers or lever pin or HELICAL.
lack of end play in the set (see Fig. 1). SPRING'__-.--- HELICAL SPRING
• Lubricate bearing surfaces with a No.2 or _ ScREw
softer graphite pencil.
Fig. 2-- SwitchhookAssembly
PLU NGER MOUNTING SCREW PLUNG
3.04 BASEPLATEFEET +1
• Feet which are badly cut, excessively worn,
or embedded with foreign matter shall be
replaced with P-11E213 molded neoprene
feet or covered with KS-8035 triangular
friction pads.
• If a foot is replaced, both feet on that end
of the set shall be equipped with neoprene
feet. Secure neoprene foot to telephone
baseplate with a P-297756 screw and a
P-11E212 nut.
END PLAY LEVER PIN END PLAY
SCREW •Felt covered feet shall be equipped with
triangular friction pads. Ifone foot is
Fig.1- Plunger Assembly equipped withafrictionpad,both feet on
that end shall be so equipped.
3.03SWITCHH00K•Friction pads shall not be attached to neo-
prene feet.
• When handset is placed on or removed from
hook, hook should move freely without 3.05 ASSEMBLY
binding or squeaking. • Unused mounting cord conductors shall be
• Binding may be caused by either a bent pin individually taped and stored.
or bent switchhook. If this trouble occurs, • Check all wiring and cords to ensure that
replace defective part. there is no interference with any moving
• Squeaks may be caused by a dirty pin. Re- parts.
move pin" clean pin and bearing holes using
' • Be sure the base is flush with the housing
a KS-2423 cloth moistened with KS-8760 before tightening base screws. ,.I
petroleum spirits.
• When reassembling, care should be taken 4.00 332 AND 334 TYPES
to be sure the undercut in the pin is assem-
bled so that the screw for the helical spring • Both sets are equipped with a lllB ampli-
engages with the undercut (see Fig. 2). tier and a 129F capacitor (see Fig. 3).
Page3

SECTIONC38.549
VOLUME
CONTROL CONTACTS
:'_il:ii ON -OFF
SWITCH
Fig. 4-Right-hand Plunger
III a AMPLIFIER 129 FCAPACITOR
ON- OFF
/CONTACTS
Fig. 311IB Amplifierand 129FCapacitor _*....!ii!_'
SWITCHHOOK
CONTACTS
• The right-hand plungeralso serves as an
on-off and volume control switch (see
Fig.4).
•Sets can be wired so the amplifier can be ,_ _'_'_i
cuteitherin orout by lifting theright-hand wi
plunger to its fullest extent.
•When testing effect of volume control with
testdesk,there should be an increase in _ ]
volume between Off, L, M, and H. If not, in-
spect volume control contacts, batteries,
and amplifier.Fig. 5--Contact Assembly
TABLEB
ii • INIIIi HI u u II mnjLm
Trouble Probable Causes Corrective Measures
--- mn ........ , ...................
Receivedoe .otmp]i yDead]oJbat;e ie Replacebatteries.
on low volume. Defective amplifier Replace lllB amplifier and 129F capacitor.
....................... _ , ...... - ......
Set howls when trans-I_andset amplifier defective Change handset.
mitter is tapped. Change lllB amplifier.
If howling recurs, change complete set.
Receiver does' not amplify Contact" troubie ........ See 4.01.............
from low to medium or
medium to high.
........ _..................... , ............... -........ ................
Mechanical or electrical Insufficient clearance be- Place two P-14_kl00 captive washers on each
trouble between the con- tween upper housing and base screw (see Fig. 7).
trol key mounted in base of set
upper housing and com-
ponent parts in the base
due to closing.
.............. i i ,, ,,, ,, ....................................
Page4

ISS 3, SECTION C38.549
.............._,,__ . :::......... !_:_!
Fig.6A -- Control on Low Fig.6B -- Control on Medium Fig.6C--Control on High
4.01 VOLUME CONTROL CONTACTS . Fig. 6A, 6B,and 6C show positions of
• If contacts test open, clean using a 265C"contacts.
tool with a clean blade. If trouble still
exists, carefully make adjustments with a 4.02 Table B lists some of the troubles that may
363 tool. If adjustment cannot be made sat- _ occur, their probable causes, and corrective
isfactorily, replace set (see Fig. 5). measures.
ARRANGE WIRING AT DIAL
AS SHOWN
PLACE TWOP-I4AIO0
WASHERS ON EACH BASE
SCREW AS SHOWNWHEN
THIS TYPE RINGER
BRACKET IS ENCOUNTERED. : _
SCREW P.181214
LOCK WASHER P-283716
RINGER8RACKET
Fig. 7--Prevention of Interference Between 6-type Dial Wiring and Ringer
Page 5

SECTIONC38.549
4.03 BATTE_RIES • Voltage should exceed 4 volts aftermeter is
connected for approximately 1 minute.
•Test by connecting leads from meter across •After checking contacts and batteries, if
terminals BK and 4 or BK and 1 if the set still fails to function, replace amplifier
right-hand plunger has to be pulled up to and capacitor.
connect amplifier in circuit. • If set still fails to function, replace set.
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