Setting the OS77 Series
The OS77 Series module must be fully installed and properly wired before
attempting any of adjustment steps. These adjustment steps must be per-
formed before the fine tuning can be accomplished and should be performed
for first time setup of the OS77.
Note for relay output models only (OS77R): The following instructions
assume terminal 5 is grounded. Relay contacts are between terminals 2& 5.
1
. Turn the “SPEED ADJ. ” potentiometer
fully clockwise (Detail 1).
2
. Remove the wire from terminal #2 of
the OS77 terminal block (Detail 2).
3
. Start engine and run at the highest
RPM desired. This is the RPM at
which the engine should be shut-
down if exceeded.
4
. Connect a Voltmeter or a test light
between terminals #1 (positive+) and
terminal #2 (negative) of the OS77 ter-
minal block. You should read no voltage
or the test lamp will be OFF.
5
. Slowly turn the “SPEED ADJ. ”
pot counter-clockwise and stop
the INSTANT the battery volt-
age is indicated on the meter
or the test light comes ON.
6
. Slowly turn “SPEED ADJ.”
pot clockwise about 1/8 of an
inch. Now, tighten the locknut
(bigger nut) on the SPEED
ADJ. pot without disturbing
the setting.
7
. Re-connect the wire to terminal
#2 on the OS77 terminal block.
This reconnects the SPEED
shutdown circuitry.
NOTE: If further adjustment (fine tuning) is needed: Turning the SPEED
ADJ. pot clockwise, RAISES
the shutdown point. This allows the engine to
run at a HIGHER
RPM. Turning the SPEED ADJ. counter-clockwise LOW-
ERS the shutdown point. This will shutdown the engine at a LOWER RPM.
Warranty
A two year limited warranty on materials and workmanship is
provided with this Murphy product. Details are available on
request and are packed with each unit.
HOOK UP AND ADJUSTMENTS
1234
5
OS77
+
+
–
–
B
Battery
To Starter
To
Starter
Key Switch
Pressure
Temp.
Rack Puller
Hold coil
Fuel Valve
Ignition Coil
Pickup
518PH/518APH
I
S
1234
OS77
+–
Battery
Pickup
169PH Magnetic Switch
1234
OS77
+
–
To Starter
Rack Puller
Hold coil
Fuel Valve
Ignition Coil
To Distributor
Ignition
R
G
NO NC
SW1
SW2
B
+–
B
Battery
To
Starter
Key Switch
Pressure
Temp.
518PH/518APH
I
S
R
G
NO NC
SW1
SW2
B
SB GC
*
Applies to 518APH model.
***
Applies to Relay output models only. B+ can be
switched on Relay output models if desired.
**
Always use shielded cable.
**
*
**
*
5
5
***
***
***
OS77 Module
Front View
Speed Adj.
Potentiometer
RaiseLower
Detail 1
OS77D Model Typical Wiring Diagram
(Negative Ground Only)
OS77I Typical Wiring Diagram
(Distributor Ignition Applications)
OS77I Typical Wiring Diagram
(For Shutting Down Magneto Ignitions)
Wiring the OS77 Series
Detail 2
WARNING: BEFORE WIRING THE OS77 MAKE SURE THE
POWER SOURCE IS OFF AND EQUIPMENT IS STOPPED.
To Pickup
To Battery–
To Battery +
Light
Meter
OR
+
--
1234
OS77 Module
Back View
■ FRANK W. MURPHY SOUTHERN DIVISION
P.O. Box 1819; Rosenberg, Texas 77471; USA
tel. (281) 342-0297 fax (281) 341-6006
e-mail sales@fwmurphy.com
■ FRANK W. MURPHY, LTD.
Church Rd.; Laverstock, Salisbury SP1 1QZ; U.K.
tel. +44 1722 410055 fax +44 1722 410088
e-mail sales@fwmurphy.co.uk
http://www.fwmurphy.co.uk
■ FRANK W. MURPHY FRANCE
tel. +33 1 30 762626 fax +33 1 30 763989
■ MURPHY DE MEXICO, S.A. DE C.V.
Blvd. Antonio Rocha Cordero 300, Fracción del Aguaje
San Luis Potosí, S.L.P.; México 78384
tel. +52-48-206264 fax +52-48-206336
e-mail murmexsl@sanluis.podernet.com.mx
■ FRANK W. MURPHY PTE., LTD.
No. 2 Tuas South Street 2,
Sprintecs Bldg., #02-01/02
Singapore 638042
tel. +65 863-1398 fax +65 863-0208
e-mail fwmsales@fwmurphy.com.sg
In order to consistently bring you the highest quality, full featured products, we reserve the right to change our specifications and designs at any time.
■ MURPHY SWITCH OF CALIFORNIA
41343 12th Street West
Palmdale, California 93551-1442; USA
tel. (661) 272-4700 fax (661) 947-7570
e-mail sales@murphyswitch.com
http://www.murphyswitch.com
■ MACQUARRIE CORPORATION
1620 Hume Highway;
Campbellfield, Vic 3061; Australia
tel. +61 3 9358-5555 fax +61 3 9358-5558
e-mail murphy@macquarrie.com.au
FRANK W. MURPHY MANUFACTURER P.O. Box 470248; Tulsa, Oklahoma 74147; USA tel. (918) 627-3550 fax (918) 664-6146 e-mail sales@fwmurphy.com http://www.fwmurphy.com
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