1967 CHEVROLET CAMARO ignition

ENGINE-ELECTRICAL 6Y-18

IGNITION SYSTEMS

INDEX

Page

General Description . 6Y-18

Maintenance and Adjustments 6Y-19

Breaker Point System 6Y-19

Breakerless System . . 6Y-X9

Ignition Coil Check 6Y-19

Spark Plugs 6Y-19

Service Operations , 6Y-19

Distributor Contact Points . 6Y-19

Cleaning 6Y-19

Replacement 6Y-20

Setting Dwell Angle 6Y-21

Distributor Condenser 6Y-22

Performance Diagnosis. 6Y-22

Replacement . . 6Y-23

Distributor

Breaker Point Type 6Y-23

Removal. . 6Y-23

Disassembly • 6Y-23
Page

Cleaning and Inspection .....'.., 6Y-25

Assembly . 6Y-25

Installation 6Y-26

Breakerless i 6Y-27

Removal . 6Y-27

Disassembly and Assembly 6Y-27

Installation 6Y-27

Off-Engine Test. . 6Y-27

Coil Replacement 6Y-27

Pulse Amplifier. 6Y-28

Disassembly .6Y-4S8

Component Checks
!
6Y-28

Assembly 6Y-29

Ignition Switch Replacement 6Y-29

Spark Plugs 6Y-30

Cleaning and Regapping I ....... 6Y-30

Installation . 6Y-31

GENERAL DESCRIPTION

There are two ignition systems available on 1967

vehicles. The breaker point type which is continued as

the regular production system and the optional (Corvette

only) transistor controlled breakerless ignition system

(magnetic pulse type). The transistor ignition system

features a specially designed distributor, control unit

(ignition pulse amplifier), and a special coil. Two resist-

ance wires are also used in the circuit; one as a ballast

between the coil negative terminal and ground, while the

other resistance wire provides a voltage drop for the

engine run circuit and is by-passed at cranking. The

other units in the system (the ignition switch, spark

plugs,
and battery) are of standard design. The dis-

tributor and control unit (ignition pulse amplifier) are

shown in Figures li and 2i.

CAP-

VACUUM

PICK-UP

COIL LEADS

PICK-UP COIL

CONNECTOR BODY
Although the external appearance of the distributor

resembles a standard distributor, the internal construc-

tion is quite different. As shown in the exploded view

(fig. 16i) an iron timer core replaces the conventional

breaker cam. The timer core has the same number of

equally-spaced projections, or vanes as engine cylinders.

The timer core rotates inside a magnetic pickup as-

sembly, which replaces the conventional breaker plate,

contact point set, and condenser assembly. The magnetic

pickup assembly consists of a ceramic permanent mag-

net, a pole piece, and a pickup coil. The pole piece
is.
a

steel plate having equally spaced internal teeth, one tooth

for each cylinder of the engine.

The magnetic pickup assembly is mounted over the

main bearing of the distributor housing, and is made to

rotate by the vacuum control unit, thus providing vacuum

advance. The timer core is made to rotate about the shaft

by conventional advance weights, thus providing centrifu-

gal advance.

Fig.
li—
Magnetic Pulse Distributor
Fig.
2i-lgnition Pulse Amplifier Unit

CHEVROLET CHASSIS SERVICE MANUAL

MAINTENANCE AND ADJUSTMENTS
ENGINE-ELECTRICAL 6Y-19

PERIODIC MAINTENANCE

BREAKER POINT SYSTEM

The distributor breaker points and spark plugs are the

only ignition system components that require periodic

service. The remainder of the ignition system requires

only periodic inspection to check operation of the units,

tightness of the electrical connections, and condition of

the wiring. When checking the coil, test with a reputable

tester.

Breaker type distributors are equipped with cam lubri-

cator and should have the wick replaced at the same time

contact point set is replaced. It is not necessary to

lubricate the breaker cam when using a cam lubricator.

Do not attempt to lubricate the wick - Replace when

necessary. When installing a new wick, adjust its posi-

tion so the end of the wick just touches the lobe of the

breaker cam.

Distributor shaft lubrication is accomplished by a

reservoir of lube around the mainshaft in the distributor

body.

BREAKERLESS SYSTEM

Since there are no moving parts in the ignition pulse

amplifier unit mounted forward of the radiator bulkhead,

and the distributor shaft and bushings have permanent

type lubrication, no periodic maintenance is therefore

required for the breakerless ignition system. The dis-

tributor lower bushing is lubricated by engine oil through

a splash hole in the distributor housing, and a housing

cavity next to the upper bushing contains a supply of

lubricant which will last between overhaul periods. At

time of overhaul, the upper bushing may be lubricated

by removing the plastic seal and then adding SAE 20 oil

to the packing in the cavity. A new plastic seal will be

required since the old one will be damaged during

removal.

Tachometer readings for test purposes can be made on

the primary circuit of the breakerless ignition system in

the same manner as on the conventional ignition system,

however before attempting to connect a test tachometer

into the primary circuit check with your instrument

supplier to insure that satisfactory readings can be

obtained and the breakerless system will not be damaged

by the tachometer that is to be used,

IGNITION COIL CHECK (BREAKERLESS)

The ignition coil primary can be checked for an open
PULSE

AMPLIFIER

IGN. SWITCH WIRE

"("IGN" TERMINAL)
-E3 IJU
12
WHITE-

-20 BLACKf' • 12 WHITE-

Fig.
3i—
Breakerless Ignition System

condition by connecting an ohmmeter across the two

primary terminals with the battery disconnected. Pri-

mary resistance at 75
°F.
should be between .35 and .55

ohm. An infinite reading indicates the primary is open.

For the engine to run but miss at times, the primary

open may be of the intermittent type.

The coil secondary can be checked for an open by con-

necting an ohmmeter from the high tension center tower

to either primary terminal. To obtain a reliable reading,

a scale on the ohmmeter having the 20,000 ohm value

within, or nearly within, the middle third of the scale

should be used. Secondary resistance at 75°F. should be

between
8,000
and 12,500 ohms. If the reading is infinite,

the coil secondary winding is open.

A number of different types of coil testers are avail-

able from various test equipment manufacturers. When

using these testers, follow the procedure recommended

by the tester manufacturer.

tester will properly
NOTE:
Make sure the

check this special coil.

SPARK PLUGS

Should be removed, inspected cleaned and regapped at

tune-up. Defective plugs should be replaced, see Servic-

ing of Units Off the Vehicle.

SERVICE OPERATIONS

DISTRIBUTOR CONTACT POINTS

CLEANING

Dirty contact points should be dressed with a few

strokes of a clean, fine-cut contact file. The file should

not be used for other metals and should not be allowed to

become greasy or dirty. Never use emery cloth to clean

contact points. Contact surfaces, after considerable use,

may not appear bright and smooth, but this is not neces-
sarily an indication that they are not functioning satis-

factorily. Do not attempt to remove all roughness nor

dress the point surfaces down smooth; merely remove

scale or dirt.

Badly burned or pitted contact points should be re-

placed and the cause of trouble determined so it can be

eliminated. High resistance or loose connections in the

condenser circuit, oil or foreign materials on the contact

surfaces, improper point adjustment or high voltages may

CHEVROLET CHASSIS SERVICE MANUAL

ENGINE-ELECTRICAL 6Y-20

cause oxidized contact points. Check for these conditions

where burned contacts are experienced. An
out-of-

balance condition in the ignition system, often the result

of too much or too little condenser capacity, is indicated

where point pitting is encountered.

REPLACEMENT

Four and Six Cylinder Engine Distributor

1.
Release distributor cap hold-down screws, remove

cap and place it out of work area.

2.
Remove rotor.

3.
Pull primary and condenser lead wires from contact

point quick disconnect terminal (fig. 4i).

4.
Remove contact set attaching screw, lift contact point

set from breaker plate.

5.
Clean breaker plate of oil smudge and dirt.

6. Place new contact point assembly in position on

breaker plate, install attaching screw.

CAUTION: Carefully wipe protective film from

point set prior to installation.

NOTE: Pilot on contact set must engage match-

ing hole in breaker plate.

7.
Connect primary and condenser lead wires to quick

disconnect terminal on contact point set. .

8. Check and adjust points for proper alignment and

breaker arm spring tension (fig. 5i). Use an aligning

tool to bend stationary contact support if points need

alignment.

NOTE: The contact point pressure must fall

within specified limits. Weak tension will cause

CONTACT SET

ATTACHING

SCREW

QUICK

DISCONNECT

TERMINAL

BREAKER PLATE

ATTACHING SCREWS
chatter, resulting in arcing and burning of-the

points and an ignition miss at high speed, while

excessive tension will cause undue wear of the

contact points, cam and rubbing block. Breaker

arm spring tension should be 19-23 ounces. The

contact point pressure should be checked with a

spring gauge. The scale should be hooked to the

breaker lever and the pull exerted at 90 degrees

to the breaker lever as shown in Figure 5i. The

reading should be taken just as the points sepa-

rate.
The pressure can be adjusted by bending

the breaker lever spring. If the pressure is ex-

cessive, it can be decreased by pinching the

spring carefully. To increase pressure,, the

lever must be' removed from the distributor so

the spring can be bent away from the lever.

Avoid excessive spring distortion.

9. Set point opening (.019" for new points).

10.
Reinstall rotor, position and lock distributor cap to

housing.

11.
$tart engine and test dwell and ignition timing.

Eight Cylinder Engine Distributor

1.
The contact point set is replaced as one complete

assembly and only dwell angle requires adjustment

after replacement. Breaker lever spring tension and

point alignment are factory set.

2.
Remove the distributor cap by placing a screw driver

in the slot head of the latch, press down and turn 1/4

turn in either direction.

3.
Remove the two attaching screws which hold the base

of the contact set assembly in place.

4.
Remove the primary and condenser leads from their

nylon insulated connection (fig. 6i) in contact set.

5.
Reverse Steps 2, 3 and 4 to install new contact set.

CAUTION:. Install the primary and condenser

leads as shown in Figure 6i. Improper installa-

tion will cause lead interference between the

cap,
weight base and breaker advance plate.

6. If car has 20,000 to 25^000 miles (or sooner if

desired) the cam lubricator wick (fig. 7i) should be

changed. Using long nosed pliers squeeze assembly

together at base and lift out. Remove all old lubri-

cant from cam surface. Replace in same manner.

Fig.
4i—Breaker Plate and Attaching Parts
Fig. 5i—-Checking Breaker Arm Spring Tension

CHEVROLET CHASSIS SERVICE MANUAL

ENGINE-ELECTRICAL
6Y-21

Fig.
6i—Distributor Lead Arrangements

NOTE:
End of cam
lubricant wick should
be

adjusted
to
just touch
cam
lobes. Over lubrica-

tion
of cam
resulting
in
grease
on
contact points

can-
be
caused
by cam
lubrication wick bearing

too hard against
cam
surface.
A
correctly
ad-

justed
cam
lubricator wick will provide adequate

lubrication
for cam. Do not
apply additional

grease
to cam
surface.

7.
Start engine
and
check point dwell
and
ignition

timing.
ACTUAL
POINT OPENING
.021

.016
FEELER GAUGE

LOCATOR ___JH^H

(ROUND)
V~^3H|

CENTRIFUGAL
\
jdft

ADVANCE
-~-»JBlMBl

MECHANISM
«H

CAM g^k. / X

LUBRICATOR
V^^^

REPLACEMENT
^£9

^-ADJUST
SQUARELY

AND
JUST

TOUCHING
LOBE

OF
CAM
.ROTOR

I^^I^BL
LOCATOR

(PBV 7
(SQUARE)

SBSSF
/

WWjga^/
^/
LUBRICATOR

H^f
CAUTION!

S5y
NEVER
OIL

•-^
CAM
LUBRICATOR-

REPLACE
WICK

WHEN
NECESSARY
Fig.
8i—Inaccurate Gauging
of
Rough Points

SETTING DWELL ANGLE

Four
and Six
Cylinder Engine Distributors

The point opening
of new
points
can be
checked with
a

feeler gauge,
but the use of a
feeler gauge
on
rough
or

uncleaned used points
is not
recommended since accurate

mechanical gauging cannot
be
done
on
such points (fig. 8i).

Contact points must
be set to the
proper opening.

Points
set too
close
may
tend
to
burn and
pit
rapidly.

Points with excessive separation tend
to
cause
a
weak

spark
at
high speed. Proper point setting
for all

models
are:

.019"
for new
points

.016"
for
used points

New points must
be set to the
larger opening
as the

rubbing block will wear down slightly while seating
to the

cam. Contact points should
be
cleaned before adjusting
if

they have been
in
service.

LATERAL

MISALIGNMENT
PROPER

LATERAL
ALIGNMENT

pCORRECT
LATERAL MISALIGNMENT
BY

M
BENDING FIXED CONTACT SUPPORT

[NEVER
BEND BREAKER LEVER

Fig.
7i—Top View
of
Distributor

Fig.
9i—Alignment
of
Points

CHEVROLET
CHASSIS SERVICE /MANUAL

ENGINE-ELECTRICAL 6Y-23

condenser leak or to a defective connection. This

will cause burned points and ignition failure upon

initial starts and at high speeds.

4.
Capacity - Capacity is determined by the area of

the metallic elements and the insulating and im-

pregnating materials.

For a complete check of the condenser, use a tester

which will check for all of the above conditions. Follow

the instructions given by the manufacturer of the

test equipment. Condenser capacity should be
.18-:
23

microfarads.

REPLACEMENT

Four and Six Cylinder Engine Distributor (Fig. 4i)

1.
Release distributor cap hold-down screws, remove

cap and place it out of the work area.

2.
Remove rotor.

3.
Disconnect condenser lead wire from contact point

quick-disconnect terminal.

4.
Remove condenser attaching screw, lift.condenser

from breaker plate and wipe breaker plate clean.

5. Install new condenser using reverse of procedure

outlined above.

Eight Cylinder Engine Distributor

1.
Remove distributor cap.

2.
Loosen condenser lead attaching screw (fig. 6i) and

lift out condenser lead clip.

3.
Remove screw holding condenser bracket to breaker

plate and slide condenser from bracket.

4.
To replace condenser reverse the above procedure.

NOTE:
Make sure that new condenser lead is

installed in proper position (fig. 6i).

DISTRIBUTOR

(BREAKER POINT TYPE)

REMOVAL

1.
On radio equipped Corvettes, remove ignition shield

from over distributor and coil. One bolt is accessible

from top of shield, the other two are at rear of

shield, facing firewall.

2.
Release the distributor cap hold-down screws, re-

move the cap and place it clear of the work area.

NOTE:
If necessary, remove secondary leads

from the distributor cap after first marking the

cap tower for the lead to No. 1 cylinder. This

will aid in the reinstallation of leads in the cap.

3.
Disconnect the distributor primary lead from the coil

terminal.

4.
Scribe a realignment mark on the distributor bowl

and engine in line with the rotor segment.

5. Disconnect vacuum line to distributor and tachometer

drive cable (Corvette). Remove the distributor hold-

down bolt and elamp and remove the distributor from

the engine. Note position of vacuum advance mecha-

nism relative to the engine.

CAUTION: Avoid rotating the engine with the

distributor removed as the ignition timing will

be upset.
Rg.
121-L-6 Distributor-Exploded View

1.
Breaker Plate Attaching

Screws

2.
Condenser Attaching

Screws

3. Condenser

4.
Breaker Plate Assembly

4a.
Cam Lubricator

5. Vacuum Control Assembly

6. Vacuum Control

Attaching Screws

7. Housing

8. Cap

9. Rotor

DISASSEMBLY
10.
Contact Point

Attaching Screw

11.
Contact Point Assembly

12.
Weight Cover

Attaching Screws

13.
Weight Cover

14.
Weight Springs

15.
Advance Weights

16. Cam Assembly

17.
Main Shaft Assembly

18.
Roll Pin

19.
Drive Gear

It is advisable to place the distributor in a distributor

testing machine or synchroscope prior to disassembly.

CHEVROLET CU
SERVICE MANUAL

ENGINE-ELECTRICAL 6Y-26

INSTALLATION-ENGINE NOT DISTURBED

(ALL MODELS)

1.
Turn the rotor about 1/8 turn in a clockwise direc-

tion past the mark previously placed on the distribu-

tor housing to locate rotor.

2.
Push the distributor down into position in the block

with the housing in a normal "installed" position

(fig. 15i).

NOTE: It may be necessary to move rotor

slightly to start gear into mesh with camshaft

gear, but rotor should line up with the mark

when distributor is down in place.

3.
Tighten the distributor clamp bolt snugly and con-

nect vacuum line. Connect primary wire to coil

terminal and install cap. Also install spark plug and

high tension wires if removed.

NOTE: It is important that the spark plug wires

be installed in their proper location in the

supports.

4.
Time ignition as previously described under Tune-

Up in Section 6.

INSTALLATION-ENGINE DISTURBED

(ALL MODELS)

1.
Locate No. 1 piston in firing position by either of two

methods described below,

a. Remove No. 1 spark plug and, with finger on plug

hole,
crank engine until compression is felt in the

No.
1 cylinder. Continue cranking until timing

mark on crankshaft pulley lines up with timing

tab attached to engine front cover.

b.
Remove rocker cover (left bank on V-8 engines)

and crank engine until No. 1 intake valve closes

and continue to crank slowly about 1/3 turn until
CENTRIFUGAL

jS ADVANCE

ROTATING

POLE PIECE

STATIONARY

POLE PIECE

MAGNETIC

PICKUP

ASSEMBLY

VACUUM

ADVANCE

DISTRIBUTOR

HOUSING

Fig.
151—Six Cylinder Engine Distributor
Fig.
16i—Magnetic Pulse Distributor Components

CHEVROLET CHASSIS SERVICE MANUAL

ENGINE-ELECTRICAL 6Y-27

timing mark on pulley lines up with timing tab.

2.
Position distributor to opening in block in normal

installed attitude (fig. 15i), noting position of vacuum

control unit.

3.
Position rotor to point toward front of engine (with

distributor housing held in installed attitude), then

turn rotor counter-clockwise approximately 1/8 turn

more toward left cylinder bank and push distributor

down to engine camshaft. It may be necessary to ro-

tate rotor slightly until camshaft engagement is felt.

4.
While pressing firmly down on distributor housing,

kick starter over a few times to make sure oil pump

shaft is engaged. Install hold-down clamp and bolt

and snug up bolt.

5. Turn distributor body slightly until points just open

and tighten distributor clamp bolt.

6. Place distributor cap in position and check to see

that rotor lines up with terminal for No. 1 spark

plug.

7. Install cap, check all high tension wire connections

and connect spark plug wires if they have been re-

moved. It is important that the wires be installed in

their location in the supports.

NOTE:
The brackets are numbered to show the

correct installation. Wires must be installed as

indicated to prevent cross firing.

8. Connect vacuum line to distributor and distributor

primary wire to coil terminal.

9. Start engine and set timing as described under Turn-

Up in Section 6.

BREAKERLESS (MAGNETIC PULSE)

DISTRIBUTOR

REMOVAL (CORVETTE)

1.
If vehicle is equipped with radio, remove three bolts

securing ignition shield over distributor and coil.

One bolt is accessible from the top of shield, the

other two are at rear of shield, facing firewall.

2.
Disconnect tachometer drive cables from distributor

housing.

3.
Disconnect pickup coil leads at connector.

4.
Remove distributor cap.

5. Crank engine so rotor is in position to fire No. 1

cylinder and timing mark on harmonic balancer is

indexed with pointer.

6. Remove vacuum line from distributor.

7. Remove distributor clamping screw and hold-down

clamp.

8. Remove distributor and distributor-to-block gasket.

It will be noted that the rotor will rotate as the

distributor is pulled out of the block. Mark the re-

lationship of the rotor and the distributor housing

after removal so that the rotor can be set in the

same position when the distributor is being installed.

DISASSEMBLY (Fig. 16i)

NOTE:
If a distributor is being disassembled

for replacement of the stationary magnetic

pickup assembly only, it will be necessary to

perform only Steps 3, 4, 5, 7, 8, 9, and 12 of the

service procedure listed below.
1.
Remove screws securing rotor and remove rotor.

2.
Remove centrifugal weight springs and weights.

3.
Remove the tachometer drive gear from the distribu-

tor (Corvette only).

4.
Remove roll pin, then remove distributor drive gear

and washer.

CAUTION: To prevent

magnet, support drive gear
;e to the permanent

?n
driving out roll

pin.

5. Remove drive shaft assembly.

6. Remove centrifugal weight support and timer core

from drive shaft.

7. Remove connector from pickup coil leads.

8. Remove retaining ring which secures magnetic

core support plate to distributor shaft bushing in

housing.

9. As a unit, remove the entire magnetic pickup assem-

bly from the distributor housing.

10.
Remove brass washer and felt pad.

11.
Remove vacuum advance unit.

12.
To reassemble distributor, perform the above steps

in reverse order.

INSTALLATION (CORVETTE)

1.
Check to see that the engine is at firing position for

No.
1 cylinder (timing mark on harmonic balancer

indexed with pointer).

2.
Position a new distributor-to-block gasket on the

block.

3.
Before installing distributor, index rotor with hous-

ing as noted when distributor was removed. Install

distributor in block so that vacuum diaphragm faces

approximately 45° forward on the right side of the

engine and the rotor points toward contact in cap for

No.
1 cylinder.

4.
Replace distributor clamp leaving screw loose

enough to allow distributor to be turned for timing

adjustment.

5. Install spark plug wires in distributor cap. Place

wire for No. 1 cylinder in tower (marked on old cap

during disassembly) then install remaining wires

clockwise around the cap according to the firing

order (1-8-4-3-6-5-7-2).

6. Attach distributor to coil primary wires.

7. Replace distributor cap.

8. Adjust timing and then fully tighten distributor clamp

screw.

9. Attach vacuum line to distributor.

10.
Connect tachometer drive cables to distributor body.

11.
Replace ignition shields.

DISTRIBUTOR OFF-ENGINE TEST

The distributor's centrifugal and vacuum advance can

be checked in a distributor testing machine or synchro-

scope specially adapted or designed to accommodate this

type distributor. However, since this involves removing

the distributor from the engine, this test may be post-

poned until other system checks have been made. A dwell

reading cannot be obtained on this distributor and it is not

likely that the centrifugal or vacuum advance will be a

cause of trouble.

COIL REPLACEMENT

1.
Disconnect ignition switch and distributor leads from

CHEVROLET CHASSIS SERVICE MANUAL

ENGINE-ELECTRICAL 6Y-28

terminals on eoil. On Corvettes equipped with radio,

remove bolts securing ignition shield over distribu-

tor and coil.

2.
Pull high tension wire from center terminal of coil.

3.
Remove the two coil support mounting bolts or loosen

friction clamp screw and remove coil.

4.
Place new coil in position and install attaching bolts

or tighten clamp screw.

5.
Place high tension lead securely in center terminal

of coil and connect ignition switch and distributor

primary leads to terminals on coil. Replace ignition

shield on Corvettes.

6. Start engine and test coil operation.

IGNITION PULSE AMPLIFIER

DISASSEMBLY

To check the amplifier for defective components, pro-

ceed as follows:

1.
Remove the bottom plate from the amplifier.

2.
To aid in reassembly, note the locations of the lead

connections to the panel board.

3.
Remove the three panel board attaching screws, and

lift the assembly from the housing.

4.
To aid in reassembly, note any identifying markings

on the two transistors and their respective locations

on the panel board and heat sink assembly.

5.
Note the insulators between the transistors.and the

heat sink, and the insulators separating the heat sink

from the panel board.

6. Remove the transistor attaching screws, and sepa-

rate the two transistors and heat sink from the panel

board.

7.
Carefully examine the panel board for evidence of

damage.

MOUNTING

SCREW

RESISTOR R5 jgSfe. / DIODE Dl

TRANSISTOR TR2

(UNDERNEATH)

1H L >©V

[So

To
I
/'%**jt\
\
TRANSISTC>R"""

1 X ^^w^ X \ (UNDERNEATH)

9^ESISTORR^^^H|^^^^^H

^B
RESISTOR
R4
^HPH^^H

WM'
RESISTOR
R3
I^B^^^^I^U

N .6 ®

mm

N%|/MOUNTING

• tr^i^w ^\ vjR SCREW

CAPACITOR
Cl\
pNkj^^A^
\
RESISTOR
Rl

MOUNTING ^55S^^ \ CAPACITOR C3

SCREW I RESISTOR R6 CAPACITOR C2

TRANSISTOR TR3
COMPONENT CHECKS (Figs. \7\ and 18i)

With the two transistors separated from the assembly,

an ohmmeter may be used to check the transistors and

components on the panel board for defects. An ohmmeter

having a 1-1/2 volt cell, which is the type usually found

in service stations, is recommended. The low range

scale on the ohmmeter should be used except where

specified otherwise.

A 25 watt soldering gun is recommended, and a 60% tin

40%
lead solder should be used when re-soldering. Avoid

excessive heat which may damage the panel board. Chip

away any epoxy involved, and apply new epoxy which is

commercially available.

In order to check the panel board assembly, it is

necessary to unsolder at the locations indicated in Fig-

ure 18i the two capacitors C2 and C3. In all of the fol-

lowing checks, connect the ohmmeter as shown and then

reverse the ohmmeter leads to obtain two readings. The

amplifier circuitry is shown in Figure 19i.

1.
Transistors TR1 and TR2: Check each transistor by

referring to Figure 20i. If both readings in Step 1

are zero, the transistor is shorted. If both readings

in Step 2 are zero, the transistor is shorted; and if

both readings are infinite, the transistor is open.

Interpret Step 3 the same as Step 2.

2.
Trigger Transistor TR3:
11
both readings in Step 1

are zero, the transistor is shorted. If both readings

in Step 2 are zero, the transistor is shorted; and if

both readings are infinite, the transistor is open.

Interpret Step 3 the same as Step 2.

3.
Diode Dl: 11 both readings are zero, the diode is

shorted; and if both readings are infinite, the diode

is open.

4.
Capacitor Cl: If both readings are zero, the capaci-

tor is shorted.

5.
Capacitors C2 and C3: Connect the ohmmeter across

CHECKING

RESISTOR Rl

UNSOLDER
I
CHECKING TRIGGER

TRANSISTOR TR3
CHECKING

CAPACITOR C

Fig.
171—Pulse Amplifier Panel Board
Fig.
18i—Pulse
Amplifier
Component
Checks

CHEVROLET CHASSIS SERVICE MANUAL