Lincoln Electric PRECISION TIG 275 Operator's Manual page 19

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• When the Polarity Switch is set to DC (- or +), the
TIG mode provides high frequency only for starting.
Hi-Freq. turns on after pre-flow time with the arc
start switch closure, and turns off when the arc is
established.*
• Also functions for DC+ polarity to permit "balling" of
tungsten for AC TIG welding.
4. AC BALANCE CONTROL – The potentiometer
control permits AC wave balance adjustment from
Max. Penetration (~85% negative wave) with the
control at Max. full CW position, to Max. Cleaning
(~65% positive wave) with the control set near min-
imum CCW position.
• Full minimum CCW position is the Auto Balance
position which is indicated by the Green panel light
turning on. This feature automatically provides the
proper amount of cleaning and penetration for nor-
mal AC TIG welding
• The mid position is the Balanced position (~50%
positive and negative waves).
• The Balance control is only functional if the machine
is set to AC polarity and TIG mode.
5. LOCAL/REMOTE CURRENT CONTROL SWITCH – A
2-position switch selects how the welding output is
controlled for both Stick and TIG Modes:
• LOCAL (Top position) selects output control only by
the machine panel Output Control. (See Item 6)
• REMOTE (Bottom position) selects output control to
also be by an Amptrol (See Item 6), or other remote
(10K pot) control connected to the Remote recepta-
cle (See Item 11). This switch selection is indicted
by the Green panel light turning on.
In either position the arc start switch functions when
connected to the Remote receptacle (See Item 11).
6. MAXIMUM OUTPUT CONTROL – The large knob
is used to set the output welding current over the
rated output range of the machine.
• With the Current Control switch to LOCAL position,
this knob sets the welding output level.
* Arc voltage and current are sensed to determine if
the arc is established or out.
OPERATION
• With the Current Control switch to REMOTE posi-
tion, this knob sets the maximum welding level that
the Peak output can be set with the remote Amptrol.
• The new MicroStart
circuit provides for low end welding (down to 2
amps) previously unobtainable on an SCR platform
TIG machine.
7. MINIMUM OUTPUT CONTROL AND DISPLAY SWITCH–
A smaller knob is used to preset the minimum cur-
rent level only for TIG mode. Pressing the Display
(momentary) switch toggle left to Minimum Set posi-
tion displays the Minimum control level setting on the
Digital meter. (See Item 8)
• This knob sets the Start output level. When the arc
lights (using a new built-in TIG start pulse) this level
upslopes quickly (0.5 sec.w/ Advanced Panel, zero
w/o-See UP Menu of Item 7a) and smoothly to the
weld output level. The setting range for this Start
control is the 2 amp minimum range of the machine
up to about 50 amps, but no more than the level set
by the Maximum Output control knob (See Item 6),
but otherwise is independent of the Maximum set-
ting.
• This setting also serves as the Crater-fill level, but
with a Precision TIG Advanced Panel it can be
selected (see Section B-7) to be either the Minimum
Output control setting (same as Start setting) as
shipped, or the minimum rating of the machine (2
amps).
• The Remote Amptrol range of control is between
this Minimum setting and the Maximum Output con-
trol knob setting, so these knobs can set the resolu-
tion of the Amptrol. Also, the Minimum setting
serves as both the minimum Amptrol start level
when the arc start switch is closed, as well as the
minimum Amptrol crater-fill level before the arc start
switch is opened to help prevent premature arc out
and Hi-Freq re-initiation.
• In STICK mode the Start control is not functional
since Hot Start level is fixed, or internal Advanced
Panel adjustable (see Section B-7). Pressing the
Display (momentary) switch toggle left to Minimum
Output position displays minimum amps rating of
the machine.
PRECISION TIG 275
Technology minimum current
TM
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