INSTRUCTION / TROUBLESHOOTING MANUAL FOR MODEL A75MD
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A75MD TROUBLESHOOTING
INSTRUCTIONS
Before troubleshooting unit, check for shipping damage. (i.e. broken wires, loose connections, etc.)
Quick-Check A75MD Trouble Analysis
Problem: Blown AC input fuse.
1. Check AC input voltage with tap setting on power transformer and control transformer. If AC input
and tap setting agree, see step #2.
2. Check AC input current draw after replacing blown AC fuse.
3. If AC input fuse clears when the AC contactor pulls in make sure the correct AC fuses are being
used, time delay fuses
4. Disconnect the secondary leads from P.T. to SCR/Diode modules. If fuse still clears, problem is in
the (P.T.) power transformer. If fuse is good, problem could be in the SCR/Diode module.
SEE SCR/SCR TROUBLESHOOTING GUIDE
5. Replace Plug and Play Assembly.
Problem: Blown DC fuse.
1. Make sure the correct type of fuse is being used.
2. Check all connections to DC fuse to be certain they are tight.
3. Check polarity of output cables and output connector.
4. Check SCR/SCR modules and diode SD4 for shorts.
SEE SCR/SCR MODULE TROUBLESHOOTING GUIDE.
5.
Replace Plug and Play Assembly.
Problem: Blown control transformer fuse CTF.
1. Defective contactor (shorted coil)
2. Control taps set wrong on control transformer H1 - H2.
3. Defective control transformer.
Problem: Contactor does not pull in.
1. Check AC input voltage and fuses.
2. Check DC voltage at DC output terminals (battery connected).
3. Check AC voltage output on control transformer.
4. If 120 Vac. is present at AC contactor coil, contactor may be defective.