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B-7
OPERATION
B-7
8. DIGITAL METER AND DISPLAY SWITCH– A 3-
digit LED meter is used to monitor the preset and
actual welding procedure based on the Display
(momentary) switch position:
• Before welding with Display switch in center (nor-
mal) position, the digital meter displays the preset
welding amps set by Maximum Output control knob
(See Item 6). If in Stick mode using REMOTE (See
Item 5.), the digital meter displays the preset weld-
ing amps set by the Remote control. (See Item 11)
• While welding with Display switch in center (normal)
position, the digital meter displays the actual weld-
ing amps with one amp resolution (XXX) and accu-
racy within 4%+/-2A of reading.
• At any time in TIG mode, pressing the Display
switch to left causes the digital meter displays the
amps preset by the Minimum Output control knob
(See Item 7).
• At any time in Stick mode, pressing the Display
switch to left causes the digital meter to display the
minimum amps rating of the machine (See Item 7).
• In either mode, while pressing the Display switch
right to Volts position, the digital meter displays
actual output volts. Volts is displayed with 0.1 volt
resolution (XX.X) and accuracy within 3%+/-1V of
reading.
9. POSTFLOW TIME – This knob is used to set the
TIG mode shielding gas postflow time over the
range of about 2 to 60 seconds after the arc is shut
off. The postflow on time status is indicated by the
Green panel light.
• Gas preflow time for TIG mode is fixed at 0.5 sec-
onds, with no panel control.
• Both time ranges are x2 extendable, if needed, by
internal control box selection. (See Section B-7)
10. THERMAL SHUTDOWN LIGHT – This yellow LED
panel light turns on if the machine output is shut-
down because internal overheating has occurred,
and turns off when the thermostat resets.
11. REMOTE RECEPTACLE – A 6-socket receptacle
is provided for the connection of an Amptrol, or
other remote control: (See Figure B.2)
• When the Current Control Switch (See Item 5) is in
the REMOTE position, the Amptrol or other remote
(10K pot) connected to the Remote receptacle con-
trols the TIG or Stick mode output within the range
preset by the Maximum and Minimum Output con-
trols. (See Item 6, 7, and 8 for meter display.)
• When the Current Control Switch is in either
LOCAL
or REMOTE
positions the arc start switch functions
when connected to the Remote receptacle.
ADVANCED PANEL CONTROLS
The following controls are included only if the Precision
TIG 275 has the Advanced Control Panel (K1829-1)
option installed: (Refer to Figure B.3 Tig Weld Cycle
Chart for graphic illustration of these TIG welding func-
tions.)
12. TRIGGER SWITCH – This 2-position switch
selects how the arc start switch ( connected to the
above Remote receptacle) functions; in 2-Step or
4-Step mode:
• DO NOT USE 4-STEP IF USING AN AMPTROL
REMOTE.
• Neither the arc start switch nor the output con-
trol in the amptrol will function normally to shut
off or control the output. ONLY USE 2-STEP.
------------------------------------------------------------------------
• In 2-Step position the arc start switch functions the
same as without the Advanced Panel:
1. Closing switch starts preflow, then a fixed
(0.5 sec.) ramp time from Minimum (Start)
setting level (See Item 7) to Weld setting.
2. Opening switch initiates Downslope ramp
time setting (See Item 17), from Weld set-
ting to Crater-fill level (See Item 7), which
then stops the arc and initiates Postflow
time (See Item 9).
Note: See Figure B.3 for 2-Step operation during
Downslope with Restart feature selected to be dis-
abled, instead of enabled (as shipped).
PRECISION TIG 275
A
B
C
D
E
F
Max
10K ohm
Min
REMOTE RECEPTACLE*
(Front View)
REMOTE OUTPUT
CONTROL
ARC START
SWITCH
*For 18-12P Plug
(LECO S12020-27)
CAUTION
FIGURE B.2
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