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B-8
OPERATION
B-8
• The 4-Step position allows welding without contin-
uously holding the start switch trigger. The arc start
switch functions in the following manner:
1. Closing the 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 the switch initiates fixed (0.5 sec.)
ramp time from Start setting level to Weld
setting.
3. Reclosing the 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 the switch after Downslope time
holds Crater-fill level until it times out, then
stops the arc and initiates the Postflow Time
(See Item 9). Reopening switch during
Downslope time immediately stops the arc
and initiates the Postflow.
Note: See Figure B.4 for 4-Step operation during
Downslope with Restart feature selected to be
enabled, instead of disabled (as shipped).
13.PULSE MODE SWITCH (PULSE / SPOT MODE
SWITCH for codes above 11000) – Turns on the
Pulse Mode as indicated by the Green panel light
turning on.
• PULSE ON position provides a Peak current level
set by REMOTE and/or LOCAL control of the output
current (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
.
• SPOT ON position provides the peak current level
set by the Maximum Output Control for a time deter-
mined by the SPOT TIME control. A red panel light
is ON to indicate SPOT mode.
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 (PULSE% ON /
SPOT TIME CONTROL for codes above 11000) •
• % ON TIME controls the duration of the peak cur-
rent 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)
• SPOT TIME sets the duration of the SPOT pulse
(0.5 to 5.0seconds on the red scale).
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
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