Tweco Thermal Arc TA 500 - Manual (Page 42)

Service 4-8 Manual No 0-0470
d. Check jumper wire in J8 connector; replace if faulty.
5. Reactor and/or transformer overheated due to ex-
ceeding the amperage rating of the Power Supply or
air flow restricted.
a. Reduce amperage to recommended ratings. Clear
air passages.
Once the Cutting Arc is established, the cutting current
reading on the Control Panel ammeter should be ad-
justable by turning the CURRENT CONTROL knob. If
it is not, there is a problem in the current regulating
circuit as follows:
N. Unit only puts out minimum current (125 A).
1. Fuse 3Fu blown.
a. Replace.
2. Fuse blows again.
a. Check diodes and SCRs in control bridge (See
J & Q, Section 4.8).
3. Potentiometer failed.
a. Check (See K, Section 4.8).
4. Reactor disconnected.
a. Check (See L, Section 4.8).
5. Current Control P.C. board failed.
a. Check (See I, Section 4.8).
6. Relay CSR not closing.
a. Bad CSR. Replace (See M, Section 4.8).
b. Loose wire on toroid (T4). Correct.
c. Bad toroid (T4). (See E, Section 4.8).
d. Check Arc Starter PC Board (See N., Section
4.8).
O. Unit only puts out maximum current (500+ A).
1. Arc Starter/Shunt P.C. board failed.
a. Check P.C. board (See N, Section 4.8). Re-
place if faulty.
2. Current Control PC Board failed.
a. Check PC Board (See I, Section 4.8). Replace
if faulty.
P. Unit can only put out about 375 amps maximum.
1. Current Control P.C. board failed.
a. Check P.C. board (See I, Section 4.8).
2. One SCR failed.
a. Check SCRs (See O, Section 4.8).
Cut quality begins okay but deteriorates during the
cutting process.
Q. Deteriorating cut quality.
1 Frozen CO2 regulator.
a. Add heater.
b. Replace with high flow regulator.
2. Cylinder not delivering.
a. Manifold several cylinders together.
If the Torch parts life is short, check:
R. Short torch parts life.
1. Pilot arc remains on during cut.
a. Check CSR (See M, Section 4.8).
2. No prepurge gas flow.
a. Check time delay relay.
3. No post purge gas flow.
a. Check time delay relay.
4. Misuse of torch.
a. Use torch with ratings for current and work
thickness.
5. Incorrect gas pressure.
a. Check and correct.
6. Inadequate coolant flow.
a. Clean filter in HE200.
b. Adjust or replace pump in HE200.
7. Restricted coolant hose or lead.
a. Remove restriction or replace hose.
S. Discolored Electrode.
1. Contaminated gas.
a. Check plasma gas system for leaks.
2. No pre or post purge.
a. Check TD1 and TD2 (See B, Section 4.8).
3. Gas hoses switched.
a. Check.