Tweco Troubleshooting Power Supply - Manual (Page 25)

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difficult to detect on a meter as it is only low for about 150 ms. If J35-6 does not
go low even momentarily but remains high at about +10 VDC, CCM is defective.
Another way to test for START is to temporarily jumper J35-6 to TP1 (CCM)
and apply CNC START. If inverter(s) come on, front panel DC LED on, no 2-5
code, then CCM is defective.
Inverter Defective.
A number of possible failures could cause no or low DC from the inverter.
Shorted output diodes. It is normal to measure 10K-20K ohms across the output,
plus to minus, of the inverters when their output cables are connected. If it is
much less, like a few ohms, one of the inverters is likely shorted. Remove either
positive or negative cables from inverter(s) output and confirm inverter still
measures shorted. If more than one inverter, disconnect and measure each one to
find the defective one(s).
Inverter no output
Disconnect arcstarter cable (so HF can’t fire) from J59 on the power supply
rear panel. Connect voltmeter between busbars under the cover on the rear panel
where the Torch (negative) and Work (positive) leads connect. Attempt to start
the unit. You would normally see 300-400 volts. It may only be there for a
second. If no voltage inverter is defective. If both Start signals are present and
no DC output, the inverter defective.
Gas Flow refer to section on Gas Controls.
2-6 AC Input Over Current
Each power supply inverter module contains two inverter sections which are in
parallel for 208 & 230V or in series for 400, 460 & 600V. Each inverter section
monitors its input current draw. If either section exceeds normal levels, the
inverter latches the signal /OCR, disables the START input inside the inverter and
sends /OCR to PCB5 on CN6-12. PCB5 sends Signal Inverter OCR to CCM on
J36-16.
/OCR from the inverter is latched in the inverter, only way to reset it is to
remove power.
Causes for 2-6 code:
• Cut demand signal to power supply exceeds 10V due to:
o Remote Analog Demand signal greater than 10V.
o Defective CCM
o Defective PCB5
• Defective inverter.
• Defective PCB5
• Defective CCM