No volts on cathode

[stokes]

I am putting together a 5E3 build for a friend. I've built a few over the years and have a real head scratcher here. Its all together and am doing prelim testing. I power it up on my current limiter and I get voltage on the plates and screens on my power tubes, the only tubes installed at this time, but I get no voltage on the cathodes and am drawing no current. When I measure the resistance from pin 8 to ground I get the 400 ohms I am using for the cathode resistor. I am using 6L6 tubes and am using the 400 ohm as a starting point, will tweak when I can see the current draw. Any ideas on where to check? Thanks for any help here.

[pdf64]

Screen grid pin 4 voltage?
The 4k7 dropper might be blown.
Zero screen grid volts results in zero mA anode current.

[stokes]

I'm showing the same voltage on the screens as the plates around 450vdc

[stokes]

And it gets deeper. I just installed the preamp tubes and they also show no voltage on the cathodes. When I check the resistance from those cathode pins to ground I get the appropriate readings, 1.5k etc. All the plates show high voltage, actually 478v's on all plates and the screens on the 6L6's.

[tubeswell]

Is your signal ground return electrically connected to the rest of the circuit? (Use R-meter to check for continuity)


And are your heater filaments working?

[stokes]

Heater filaments are working, 6.3 on all tubes, 5v on rect. I'm not running any signal yet, what exactly do you mean by "signal ground return"? Since all cathodes are measuring proper resistance to ground I am assuming there is some kind of ground issue, but what could it be?

[pdf64]

Are the 6L6 heaters getting hot?

[AlNewman]

Are you using a bus bar of some sort?

[Merlin]

Check for continuity between the power transformer centre tap and circuit ground.

[stokes]

DOH! It was bugging me that when I put the preamp tubes in, they also had no volts on the cathodes. I just went and checked the heater voltages at the tubes.... head slap, I had 6.3 at the pilot light and just assumed...... I always wire up the heaters first before I start the other connections so the heater wires are at the bottom of the chassis and out of the way. I forgot that I left the connection from the pilot to the tubes to do last so I'd have room to work in that tight chassis. I'll connect it up after dinner and I'm sure it will be fine. Thanks for all the replies and I appologize for leading you guys on a wild goose chase.

[stokes]

All good now. That was a serious senior moment for me.