too much preamp voltages

[yalesmith]

I had this problem before and it was because the tubes were not drawing any voltages, a result of a grounding issue. The plate voltages are 292volts on the on the preamp tubes, the same voltage coming off the filter caps? any ideas? Also, the amp is a rocket and the power tubes voltages are perfect.

Thanks

[Firestorm]

If I understand you correctly, you're saying that the voltage on both sides of the plate resistor is 292VDC, meaning that no voltage is being dropped, which in turn means that no current is flowing in the tube. That, too, would likely be a grounding problem. What is the cathode voltage?

[yalesmith]

exactly my issue...and no voltages on the cathode.

[surfsup]

All your cathodes? Just one? Do you have a connection to the Rk still? is the resistor grounded on the other end? Does the resistor measure correctly? Do you have a Ck on this cathode? Has it shorted to ground? Did you try to disconnect it temporarily? Do you have filament voltage on the preamp tube(s) in question? Can you be more specific?

[yalesmith]

all cathodes are zero. and the filaments are 3.3v at both pins. cathode are grounded correctly and the cathode bypass is grounded as well (which i believe it is correct) I will try disconnecting the cathode bypass.....Also these issues are on all of the preamp tubes....

Thanks

[Structo]

What are you grounding the cathodes to?

[surfsup]

To follow up on structos comment, are they grounded to a bussbar and is the bussbar grounded somewhere to the chassis? Gutshot? You said you have this problem before. Did this amp function before, or a diferent amp? If this amp, what did you change?

[yalesmith]

Yes there is a buss bar and it is grounded to the chassis. I had this happen before to another amp and I don't remember whatt he issue was.

[yalesmith]

Gut shots

[yalesmith]

gut shot 2

[surfsup]

I dont see any bad connections from the photos but you didnt post a photo showing the cathode grounding. Can you take a photo of the area between the pots and the board that shows your grounding?

[yalesmith]

another shot...

[Firestorm]

Are the PI voltages off too? What is the measured resistance from the grounding buss to the cathodes of your filter caps?

[yalesmith]

PI is all off as well. I apologize but what are the cathodes of my filter caps mean?

[Firestorm]

PI is all off as well. I apologize but what are the cathodes of my filter caps mean?

The "minus" end of the caps, which should be at some ground potential.