Measure cathode current in Crate Blue Voodoo

[disorder]

Have a Crate Blue Voodoo here that needs new 6L6's. It's the 60 watter the BV60H.

The power tubes have fuses between the cathodes and ground. Could I replace one of these fuses with a 1ohm resistor to measure cathode current?

[Jazz P Bass]

Yup.
Or put your meter across the empty fuse holder.
Measuring current, of coarse.

[disorder]

thanks JPB. I have one more question. the tubes measured fine but I'm a little worried about the plate voltage. it's right at 500V which I know the new JJ 6L6GC's I'm using will handle but the schematic says the plate voltage should be 460V. Is the 40V increase evidence that theres something fishy going on in the B+ line/filtering ? I ask because after I biased the amp up to ~33mA at 500V I played it for a good while, sounded good. I then gave the amp back to my friend and he said after about 30 minutes of beating down on the amp it stopped working. I got it back and both cathode fuses were blown. Replaced them, turned the amp back on, and the bias was still right where I set it. What would cause those fuses to blow?

[Billy R aka DynaFreak]

The blue voodoos Ive worked on were all right near 495 plate volts, so I dont think that is your problem. the fuses blew because the tubes were drawing too much current, which could be caused by a number of things. first question, what kind of cabinet was your friend using? are the cables OK? no need for you to keep fixing the amp if his rig is causing the problem. that being said, be sure you test the amp at full output with dummy load and oscope while monitoring cathode current, and plate voltage, that will help figure it out. You can check the basic health of your B+ filtering by measuring AC voltage at the filter cap. Its usually 1-2 volts at the first node.