Lowering B+ using a Zener Follower if the Bias comes from a tap what happen ?

[kagliostro]

I'm unsure

using a Zener Follower in this way as to lower B+



if there is a tap for the bias on the HV winding, does it increases or not ?  

I would be tempted to say no, but I'm not sure  

Also:

the - (minus) isn't connected to ground so there will be a floating supply is this detrimental in a guitar amp ?

K

[jjasilli]

dejas vu???  http://www.el34world.com/Forum/index.php?topic=13263.0

[kagliostro]

dejas vu???

not exactly, I'm considering the way of connection exactly as in the schematic I attached, the - (minus) of the Power Supply in the schematic of the image isn't grounded

I can understand the bias voltage will vary if the - (minus) is connected to ground, but what happen with a floating power supply ?

K

p.s.: sure I'm missing something, but what ??

[jjasilli]

I don't know how to wire the Transistor, BUT quoting Sluckey in the other thread: "Put the zener in the B+ line rather than the transformer center tap. Then only the B+ will be affected." 

OTOH, it occurs to me that: 1) with a zener in the CT, there still might be enough voltage remaining in the bias tap; or 2) you could ignore the bias tap & source bias voltage off the HT secondary.

[John]

dejas vu???

not exactly, I'm considering the way of connection exactly as in the schematic I attached, the - (minus) of the Power Supply in the schematic of the image isn't grounded

I can understand the bias voltage will vary if the - (minus) is connected to ground, but what happen with a floating power supply ?

K

p.s.: sure I'm missing something, but what ??

That looks like a Merlin drawing, and I believe he often does not draw in the ground symbol, taking for granted the reader knows that the bottom "wire" is grounded. If so, then it's not floating after all.

[kagliostro]

I confirm the source of the schematic and, yes, I know that usually there is a ground connection

I was only wondering about what will happen with a floating PS

K

[John]

I was only wondering about what will happen with a floating PS

Oh, sorry! Misunderstood.

[jjasilli]

The PS is not floating in that drawing.  The faded background shows that the CT is connected to ground through a zener circuit which has been made variable.  The two outer legs of the PT are conventionally rectified.

[kagliostro]

The PS is not floating in that drawing.  The faded background shows that the CT is connected to ground through a zener circuit which has been made variable.

Don't want contradict you, sorry, but the circuit didn't report a ground connection (I've the book on my hand)

what you see faint under the write "by up" is a ground symbol reported on the back of the page

however, as told, i was wondering about a floating PS with a Zener Amplifier and a Bias tap

K

[sluckey]

however, as told, i was wondering about a floating PS with a Zener Amplifier and a Bias tap

To me 'floating' means no part of the power supply is connected to chassis. If that's not what you mean, please explain. Otherwise, it makes no difference whether the PS is floating or is connected to chassis. The zener (or zener/transistor) in the CT of the PT HT winding will have the same effect on the bias supply ***IF*** the bias winding is tapped from the HT winding and shares the CT.

[kagliostro]

Ciao Sluckey

To me 'floating' means no part of the power supply is connected to chassis.

I mean the same

The zener (or zener/transistor) in the CT of the PT HT winding will have the same effect on the bias supply ***IF*** the bias winding is tapped from the HT winding and shares the CT.

Many Thanks for the clarification

K