250VDC Chassis to Input Jack Negative !!! SHOCK hazard

[Cygnus X1]

I'm getting full B+3 250VDC between circuit ground and the chassis on a new 5F1 Champ build.
That's 250VDC between the neg of the input jack and chassis.

Input jack is isolated.

Circuit is NOT grounded to the chassis.

Using a center tapped transformer with two 5407 diodes and a 500R dropping resistor.
No tube recto, don't have room for it.
Everything else looks normal.



Thoughts?

[Enzo]

Let me get this straight, none of the amp circuitry is grounded to the chassis?

I can't see in your photo, but is the high voltage power transformer center tap grounded to chassis? If so, then without a circuit common to chassis connection the whole circuit will float up to B+ because it has no path to ground.

You need to ground your circuit.

[Cygnus X1]

CT is not attached to the chassis.
It is the negative reference.
Speaker and input jack are both isolated.

You're saying to attach the CT to the chassis?
Or all to chassis?

Thank you Enzo.

[Cygnus X1]

Attached a jumper between the center tap and the chassis.
No voltage between ground and chassis now, but it made bad popping noises and no sound went through.

Now what?
Tie the jacks to the chassis?

[Cygnus X1]

Guess I got ahead of myself.
After the popping, I removed the jumper between the CT and the chassis.

Now I'm getting nothing, apparently fried something?

At least it was pushing a signal before!
Now, just dead.

[n8b]

What tube are you using for the preamp? The wiring doesn't look right for a 12ax7.

[Cygnus X1]

It's a 12AX7 alright.
Only deviation from 5F1 is the SS rectifier and the dropping resistor associated with that string.

Turned out right when I put the CT to chassis it fried the output transformer.
That's what killed it, likely old OT I was reusing was close to its last legs anyway.

Replaced the OT and now it's down to fine-tuning.
Negative is tied to chassis now.
Neg feedback is in place, all voltages read in spec.

I get spoiled by the odd design of the AX84 SEL where I do not tie to chassis at all.
I use a full wave bridge (4 diode) with an artificial CT.
Filament ground is lifted on that design as well.
Messes me up when I get into conventional designs, odd but true.
But...the SEL is VERY quiet for background noise and I have to put up the with usual
hums and hisses associated with Leo's designs.
Now I will look at lifting the filaments with 100 ohm resistors, etc.
I went ahead and twisted the AC wires but really not much difference in hum.

EDIT.
Most of the hum is associated with the pot.
When I turn the volume up the hum disappears.
Another shaky ground to chase.
This is GOOD, I can handle it.

[Cygnus X1]

Sorted out and finished.

Here is what she is:



RCA radio, sounds good!

Thanks for all the assistance.