Tweco 151 with SL100SV - Manual (Page 85)

Manual 0-4691 5-17 SERVICE
5
F. Gas flows; AC indicator ON; GAS and DC indicator OFF
1. Gas pressure too low
a. Set operating pressure per pressure setting label on power supply.
NOTE
Minimum pressure for power supply operation is lower than minimum required for torch operation.
2. Faulty Pressure Switch
Measure for 12 vdc from wire #10 to wire #11 at the Gas Pressure Switch, located on the right side of the unit. Refer to
System Schematic in the Appendix pages.
a. If 12 vdc is present and pressure is above 50 psi (3.4 bar), replace Gas Pressure Switch/Solenoid Assembly. Refer to
Section 5.08-A.
b. If pressure is above 50 psi (3.4 bar) and 12 vdc is not present, replace the Logic PC Board.
3. Faulty Wiring or Faulty Logic PC Board
Check for 12 vdc at Main PC Board pin J24-3 to J24-4 from the Logic PC Board. Refer to Appendix Pages, Main PC Board
Layout.
• If less than a volt, replace Logic PC Board.
G. Gas continues to flow with RUN / RAPID AUTO RESTART / SET switch in RUN position.
1. Damaged gas solenoid.
a. Turn the front panel ON/OFF switch to OFF.
• If gas continues to flow, debris from the air line is preventing the solenoid from closing. Clean or replace the solenoid.
2. Faulty RUN / RAPID AUTO RESTART / SET switch.
a. Remove one wire from the pressure switch. Check for ± 0 vdc at Main PC Board pin J24-3 to J24-4 from the Logic PC
Board. Refer to Main PC Board Layout.
• If less than a volt, replace Logic PC Board.
3. Faulty Logic PCB.
a. Measure for approximately 12 vdc between P1-7 and TP-1 on the Logic PCB.
• If 12 vdc is present, replace Logic PCB.
• If less than 2 vdc, replace Main PCB.