Tweco Thermal Arc TA 500 - Manual (Page 41)

Manual No 0-0470 4-7 Service
H. No red DC POWER Light.
1. Pressure switch PS3 in Supply Console not satis-
fied.
a. Check gas pressure setting (Plasma 60 psi/
4.1 bar).
2. Pressure switch out of adjustment.
a. Reset (See A, Section 4.8).
3. Main transformer overheated.
a. Allow to cool down.
4. Faulty main contactor (W).
a. Check contactor (See D, Section 4.8).
The Pilot Arc should start 2 seconds after the red DC
POWER Light comes on. If it does not, check the torch
parts to make sure they are in good condition and prop-
erly assembled. Next, check the Arc Starter unit for
loose connections and components for obvious failures.
Check to see if:
1) There is any “click” inside the Power Supply at the
time the Pilot Arc should start (2 seconds after pushing
START button).
I. No “click” inside the Power Supply 2 seconds
after the START button is pushed.
1. Faulty time delay TD2.
a. Check TD2 (See B, Section 4.8).
2. Faulty pilot control relay (PCR)
a. Check PCR
J. No Pilot Arc (or intermittent).
1. Damaged (defective) Torch parts.
a. Replace.
2. Dirty (wet) Plasma gas.
a. Purge.
b. Check for leaks on hoses and fittings.
c. Replace gas cylinders.
K. No Pilot Arc at all.
1. Blown pilot fuse (1Fu or 2Fu)
a. Replace.
2. Pilot contactor (PCR) not closing
a. Check PCR
3. Broken conductor in lead
a. Replace lead.
4. Loose connection
a. Repair.
5. Gas purge relay (TD2) not closing
a. Replace TD2.
6. CSR activating prematurely.
a. Check for shorted toroid (See E, Section 4.8)
or bad relay P.C. board.
7. Pilot Bridge diodes (D17, 18, 19, 20) failed.
a. Check diodes (see G, Section 4.8, and Q, Sec-
tion 4.8).
8. Arc Starter transformer (T3) failed.
a. Check (See F, Section 4.8) and replace.
9. Diodes in Arc Starter Box shorted or open.
a. Check (See G, Section 4.8).
10. Arc Starter failed.
a. Replace.
L. Weak Pilot Arc.
1. Faulty Arc Starter/Shunt PC Board
a. Check PC Board (See N, Section 4.8). Replace
if needed.
2. Dirty coolant in HE200
a. Check HE200 deionizer cartridge (Section
4.3)
The Cutting Arc should start as soon as the torch, with
Pilot Arc running, is brought to within about 1/2 inch
(12 mm) of the workpiece. If it does not, check:
M. No Cutting Arc.
1. Work Cable not connected.
a. Connect.
2. One leg of 3 phase primary power out.
a. Check all 3 input phases for voltage.
3. One leg of main contactor (W) not closing.
a. Check voltage at diodes.
4. Main contactor (W) fails to operate.
a. Check relay (1CR); replace if needed.
b. Check thermal protection switch (TP1, 2, 3);
replace if needed.
c. Replace contactor.