Lincoln Electric PRECISION TIG 275 IM702-A Operator's Manual page 21

B-6
• In 4-Step position allows welding without continu-
ously holding the start switch trigger. The arc start
switch functions in the following manner:
1. Closing switch starts preflow, then arc starts
at Minimum (Start) setting level (See Item
7). If the trigger is maintained closed after
preflow time the output remains at the Start
level until it is released.
2. Opening switch initiates fixed (0.5 sec.)
ramp time from Start setting level to Weld
setting.
3. Reclosing switch initiates Downslope ramp
time setting (See item 17) from Weld setting
down to the Crater-fill level (See Item 7) of
the machine.
4. Reopening switch after Downslope time
holds Crater-fill level until switch opens,
then stops the arc and initiates the Postflow
Time (See Item 9). Or, reopening switch
during Downslope time immediately stops
the arc and initiates the Postflow.
Note: See Section B-7 for 4-Step operation during
Downslope with Restart feature selected to be
enabled, instead of disabled (as shipped).
13. PULSE MODE SWITCH – Turns on the Pulse
Mode as indicated by the Green panel light turning on.
• Pulsing provides a Peak current level set by
REMOTE and/or LOCAL control of the output cur-
rent (See Item5), for a time determined by the Pulse
Frequency Control setting (See Item 14) and the %
ON Time (See Item 15). The balance of the cycle
time is at the Background Current level (See Item
16).
• Pulsing begins after upslope when the output cur-
rent rises above the Background Current level and
ends when the output current drops below this level.
14. PULSE FREQUENCY CONTROL – This knob is
used to set the Pulse Frequency over the peak pulse
range of about 0.1 pps to 20 pps. (One pulse cycle
time = 1/pps = 10 to .05 sec. range.)
15. PULSE % ON TIME CONTROL – This knob con-
trols the duration of the peak current as a percentage
(5% to 95%) of one pulse cycle. The balance of the
cycle time will be at the Background Current setting.
(See Item 16)
OPERATION
16. PULSE BACKGROUND CURRENT CONTROL –
This knob controls the level of the Background Current
as a percentage (MIN.-100%) of the Peak (REMOTE
and/or LOCAL) output level (See Item 6) down to the
Minimum Output setting (See Item 7).
17. DOWNSLOPE TIME– This knob is used to set the
time, over the range of zero to about 10 seconds, to
ramp down from weld setting to Crater-fill level (See
Item 7).
• If the arc goes out after the Downslope time is initi-
ated, the Downslope time is interrupted and the
Postflow time is initiated. This prevents Hi-Freq re-
initiation during ramp down crater fill
• When using an Amptrol remote control, where the
downslope is controlled by the operator down to the
crater-fill level, the Downslope time should be set to
zero so as not to have the Downslope time delay
when the arc start switch is opened.
PRECISION TIG 275
B-6