Extremely high B+ throughout whole amp

[clyde]

Princeton AA964 build, my first in awhile due to relocation and health issues.  On a Filmosound chassis, I had this issue previously and left it for awhile, redid the power supply and it fired up this morning, beautiful.  I changed out tubes and now I have 498v throughout the amp, plates, screens preamp everywhere.  I'm thinking something isn't grounding, internal to the PT?  The PT is Filmosound original 360-0-360, but with a 5Y3 it was almost dead-on to factory AA964 voltages earlier today.   

[Dave]

Are you sure that when you changed the tubes that you didn't stick in a 5AR4 by mistake?


Dave

[labb]

That number would indicate that none of the tubes are conducting. It is as though you have no tubes installed.

[Latole]

Princeton A964 schematic show PT 340-0-340 volts. You have 20 volts over on both side.
And what is the current (power ) of this PT ? For Princeton you need no more than 70 ma

You PT could be too powerfull and may fit with Tremolux or Vibrolux who need same voltage with 180 ma ?

Or 6V6 bias is too cold ?

I often use zener diodes to reduce B+ voltage when I built amp from scratch.

Zener diodes for reducing B+

https://robrobinette.com/Generic_Tube_Amp_Mods.htm#B+1_Voltage

https://el34world.com/Forum/index.php?topic=25996.0

https://el34world.com/Forum/index.php?topic=17595.0

https://www.tedweber.com/v-dump

[Latole]

That number would indicate that none of the tubes are conducting. It is as though you have no tubes installed.

+1
Or Power supply see no tubes. ?

[2deaf]

Are the heaters lighting up?

[Williamblake]

And what heater voltage are you reading?

[clyde]

Heater volts are fine, bias voltage is fine.  500v more or less at every B+ node, dropping resistors do nothing. 

[tubeswell]

Heater volts are fine, bias voltage is fine.  500v more or less at every B+ node, dropping resistors do nothing.

Then suspect you’ve missed a critical signal ground connection. With your R-meter, check for DC-continuity between each (lead of every component* with a) ground return lead, and the chassis. You’re looking for open readings


*including all the filter caps, grid leak resistors, cathode resistors and volume pots etc

[labb]

What Tubeswell said..what is your grounding scheme? First check I would make would be from the cathode pin of each tube to ground.to the chassis, not your ground point connection.  Do with the power turned off to the amp.

[clyde]

Thanks guys, I suspected it was grounding somewhere.  This is not my first rodeo by far.  I'll ground every connection by clip lead and get back to you.  Darn!

[clyde]

Heater wire was floating around in one of the pins loose, made contact just often enough to piss me off.  After a long layoff I've lost my edge.  Thanks everyone!