Safely lower B+

[gtrbryan]

I have an old PA that I converted into a champ with lots of bells, whistles and switches. The PT is 360 secondary for 110v. I'm getting about 485.  I am using a 5Y3 and am getting more volts out of it than I would expect. I'm going to try another 5y3 and see if it brings it down.

If I need to knock it down further, I have a 200 ohm 25 watt resistor.  Anyone see any problems in putting that  between the 5y3 and the first filter cap?

[stratele52]

Resistor will give too much sagg and voltage will vary with power output. Better use some Zener diodes ( 10 volts , 5 watts at $0.50 each ) .

You put some in series with the center tap ( B + ) on your power transformer,

[kagliostro]

If the amp is an SE, no much worry about SAG

K

[stratele52]

Yes , but only  if the amp work in ( real ) class A.

[Willabe]

Yes , but only  if the amp work in ( real ) class A.

His amp is SE Champ type, it has to work in real class A.


              Brad     

[tubeswell]

Nevertheless, if you can't lower it with a proper 5Y3GT rectifier, then some reverse-biased zeners in series with the HT winding's CT and the ground are the simplest way to go. Use 9V, 12V, or 15V zeners with a 5W rating, and put them in series (banded end(s) pointing to ground)

[stratele52]

Yes , but only  if the amp work in ( real ) class A.

His amp is SE Champ type, it has to work in real class A.


              Brad     

No , We have to check bias to say . Class A is not only a cathode with a resitor . Tube should operate at a very high current too. Resitor and tube must be matched.

That 's why I write " a real Class " 

[stratele52]

Nevertheless, if you can't lower it with a proper 5Y3GT rectifier, then some reverse-biased zeners in series with the HT winding's CT and the ground are the simplest way to go. Use 9V, 12V, or 15V zeners with a 5W rating, and put them in series (banded end(s) pointing to ground)

This is my opinion too : ......the simplest way