Using High Frequency Arc Starter with DC machine

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I have a Century 295 AC/DC machine with HF arc starter/stabilizer on it and was welding away last week on DC when the machine quit.  I can't get an arc to start at all on DC, but it works fine on AC.  From the little research I've done am thinking it is likely a bad diode on the rectifier.  My question relates to using the HF arc starter on DC.  I've been using the HF arc starter all the time I weld as I feel it helps stabilize the arc a bit.  Could the HF back feed into the machine on DC and burn out the diodes?
Reply:I'm not sure about diodes per se, but use of HF does require a capacitor(s).  Read through this thread, especially the last post:https://weldingweb.com/vbb/threads/2...citor-questionFrom my old Lincoln Idealarc 250 manual:

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Reply:That machine is suppose to be AC only, so there is a add on box for DC and the HF start?Retired - Refrigeration Pipefitter - Master Electrician-  IowaLots of Hobbys
Reply:

Originally Posted by DRussell

I have a Century 295 AC/DC machine with HF arc starter/stabilizer on it and was welding away last week on DC when the machine quit.  I can't get an arc to start at all on DC, but it works fine on AC.  From the little research I've done am thinking it is likely a bad diode on the rectifier.  My question relates to using the HF arc starter on DC.  I've been using the HF arc starter all the time I weld as I feel it helps stabilize the arc a bit.  Could the HF back feed into the machine on DC and burn out the diodes?
Reply:Yes, you are correct. There are four diodes on it. The HF unit is a separate unit attached to the front with it's own 110 volt power supply and switch.The HF unit has two short leads which plug into the welder. The the welder leads plug into the HF unit instead of the actual welder.The welding amperage passes through the HF unit and it will weld without the HF unit being on. You don't have to unplug/plug leads to weld with it or without it.
Reply:What causes the diodes to fail?
Reply:

Originally Posted by DRussell

What causes the diodes to fail?
Reply:If stuck rods makes them fail then using the HF unit should help. It does make it easier to start the arc.
Reply:

Originally Posted by DRussell

If stuck rods makes them fail then using the HF unit should help. It does make it easier to start the arc.