Hyperterm Powermax 1000 inverter issue

[YYeahoo]

I'm having an issue with Powermax 1000. Using tips from this forum and others, I have found a problem. Many thanks to Jim Colts comments on this forum. The symptoms: the torch fires when unit first turns on but becomes intermittent then only spits when trigger pulled.

Using Test 2 in the service manual I have found an open power resistor R120 in the inverter section. This unit is s/n 1000-009765 so the unit is old. I have found some interesting voltage anomalies associated with Q6, Vbus, R119, C98, R120, C94. The voltage between Q6 collector 1(C1, top screw) and Emitter 2 (E2, mid screw ) stays at the advertised 750vdc. However the measurement between the bottom screw of Q6 and either the top or middle screw the voltages do not stay at the 375vdc. The voltage between top screw and bottom screw gradually drops to 140- and the voltage between middle screw and bottom screw gradually increases 600+.

I was just curious if anyone has had this problem. I have ordered a replacement resistor and hoping this fixes it. I let everyone know the out come.

[adbuch]

I am not familiar with your particular machine, but I would be very interested to know if replacing the bad power resistor fixes your problem. Please let us know.
Thanks,
David

[YYeahoo]

David, Yes it fixed my problem. There is service bulletin from Hypertherm that makes the replacement of R119 and R120 very easy. I replaced both resistor because R120 was open and R119 was out of tolerance.
BTW I have some extra resistors if anyone has a problem with R119 and R120.

[adbuch]

Thanks for the update! I am happy to hear you've got it fixed.
David