Lincoln Na5 Service Manual

E-4THEORY OF OPERATIONE-4
CONTROL, LOGIC AND 
PROCEDURE BOARDS
The logic board interprets and processes the signals it
receives from the various PC boards, switches and con-
trols.  The logic board also houses a DC power supply
(+5 -10) which is derived from the 22VAC received from
the T2 transformer.  This DC voltage is also used on the
procedure board. 
Upon receiving voltage reference level commands from
the procedure and voltage boards, or the user-operated
switches, the logic board sends the...

E-5THEORY OF OPERATIONE-5
OPTIONAL START, CRATER
FILL AND WELD TIMER
BOARDS
When installed, the optional start board
dictates to the procedure board the
starting wire feed speed and arc volt-
age.  This condition can be operator set
for a predetermined period of time.
These parameters can be set either
higher or lower than those of the weld-
ing procedure to control penetration,
bead shape, or other factors at the start
of the weld.  The start circuit becomes
active when the weld current sensing
reed...

E-6THEORY OF OPERATIONE-6
NA-5
SCR OPERATION
A silicon controlled rectifier (SCR) is a three terminal
device used to control rather large currents to a load.
An SCR acts very much like a switch.  When a gate
signal is applied to the SCR it is turned ON and there
is current flow from anode to cathode. In the ON state
the SCR acts like a closed switch. When the SCR is
turned OFF there is no current flow from anode to
cathode thus the device acts like an open switch. As
the name suggests, the SCR is a...

NA-5SECTION F-1
TROUBLESHOOTING & REPAIRSECTION F-1
TABLE OF CONTENTS 
-TROUBLESHOOTING AND REPAIR SECTION-
Troubleshooting and Repair ........................................................................\
..............................Section F How to Use Troubleshooting Guide........................................................................\
..............................F-2
PC Board Troubleshooting Procedures ........................................................................\...

WARNING
NA-5F-2
TROUBLESHOOTING & REPAIRF-2
This Troubleshooting Guide is provided to
help you locate and repair possible machine
malfunctions.  Simply follow the three-step
procedure listed below.
Step 1. LOCATE PROBLEM (SYMPTOM).
Look under the column labeled “PROBLEM
(SYMPTOMS)”.  This column describes
possible symptoms that the machine may
exhibit.  Find the listing that best describes
the symptom that the machine is exhibiting.
Symptoms are grouped into the following
categories: wire feeding...

NA-5F-3
TROUBLESHOOTING & REPAIRF-3
_______________________________
CAUTION:
Sometimes machine failures
appear to be due to PC board failures.  These
problems can sometimes be traced to poor
electrical connections.  To avoid problems
when troubleshooting and replacing PC
boards, please use the following procedure:
1. Determine to the best of your technical ability that the PC board is the most likely
component causing the failure symptom.
2. Check for loose connections at the PC board to assure that the...

F-4TROUBLESHOOTING & REPAIRF-4
NA-5
Observe all Safety Guidelines detailed throughout this manual
If for any reason you do not understand the test procedures or are unabl\
e to perform the tests/repairs safely, contact the Lincoln Electric
Service Department for technical troubleshooting assistance before you p\
roceed. Call 216-383-2531 or 1-800-833-9353.
CAUTION
WIRE FEEDING PROBLEMS
PROBLEMS
(SYMPTOMS)POSSIBLE AREAS OF
MISADJUSTMENTS(S)RECOMMENDED
COURSE OF ACTION
The wire feeds whenever the input...

F-5TROUBLESHOOTING & REPAIRF-5
NA-5
Observe all Safety Guidelines detailed throughout this manual
If for any reason you do not understand the test procedures or are unabl\
e to perform the tests/repairs safely, contact the Lincoln Electric
Service Department for technical troubleshooting assistance before you p\
roceed. Call 216-383-2531 or 1-800-833-9353.
CAUTION
WIRE FEEDING PROBLEMS
PROBLEMS
(SYMPTOMS)POSSIBLE AREAS OF
MISADJUSTMENTS(S)RECOMMENDED
COURSE OF ACTION
The wire does not feed.  Pressing
any...

F-6TROUBLESHOOTING & REPAIRF-6
NA-5
Observe all Safety Guidelines detailed throughout this manual
If for any reason you do not understand the test procedures or are unabl\
e to perform the tests/repairs safely, contact the Lincoln Electric
Service Department for technical troubleshooting assistance before you p\
roceed. Call 216-383-2531 or 1-800-833-9353.
CAUTION
WIRE FEEDING PROBLEMS
PROBLEMS
(SYMPTOMS)POSSIBLE AREAS OF
MISADJUSTMENTS(S)RECOMMENDED
COURSE OF ACTION
The wire will not feed and the...

F-7TROUBLESHOOTING & REPAIRF-7
NA-5
Observe all Safety Guidelines detailed throughout this manual
If for any reason you do not understand the test procedures or are unabl\
e to perform the tests/repairs safely, contact the Lincoln Electric
Service Department for technical troubleshooting assistance before you p\
roceed. Call 216-383-2531 or 1-800-833-9353.
CAUTION
WIRE FEEDING PROBLEMS
PROBLEMS
(SYMPTOMS)POSSIBLE AREAS OF
MISADJUSTMENTS(S)RECOMMENDED
COURSE OF ACTION
The wire will not feed when the inch...