Need some help with an antique welder

[Leaksoup]

My neighbor has a 30kW rf welder with telefunken rs1064c tube, so it's almost biblically old. My forte is solid state so you can guess why I need some help with this. The problem is that welder turns on and technically works, but it has no output. Just sitting there humming and getting hot. Anyone have an idea why this is happening?

 

[VoltWise]

It seems like the tube isn't workin right, maybe it's not getting a signal, the tuning is off, or it's just worn out. Those RS1064Cs can go bad without clear symptoms. I'd start by checking the grid voltages and the drive stage.Have you gotten any measurements from it yet?

 

[Leaksoup]

I haven't yet, thanks for the tip. What exactly should I measure?

 

[poseidon't]

I haven't yet, thanks for the tip. What exactly should I measure?

Start with the basics: check the filament voltage, grid bias, and plate voltage. If those are in spec, see if the drive signal is getting to the grid. No signal means no output.