[Jon Yaeger]

In designing the Eico CF and trying to incorporate ideas from the group, I
am wondering how it might be possible to elevate the heater potential for
just the pair of cathode followers?

I know how to elevate the entire heater string, but I don't think that I
want to.

The transformer has a pair of 6.3 VAC filament windings - one side per
channel. It also has a 5V winding for the rectifier.

In bantering about some possibilities, I wonder if it would be a bad idea to
use the 5V winding for the 6CG7s, and elevate that potential . . . meaning
that the rectifier heater would also be at a higher potential, and the 6CG7
would consume an extra 0.6 amps.

Ideas?

Thanks.

Jon

[Jon Yaeger]

in article ,
Bret Ludwig at wrote on 12/3/07 3:54 PM:

On Dec 3, 2:30 pm, Jon Yaeger wrote:
In designing the Eico CF and trying to incorporate ideas from the group, I
am wondering how it might be possible to elevate the heater potential for
just the pair of cathode followers?

I know how to elevate the entire heater string, but I don't think that I
want to.

The transformer has a pair of 6.3 VAC filament windings - one side per
channel. It also has a 5V winding for the rectifier.

In bantering about some possibilities, I wonder if it would be a bad idea to
use the 5V winding for the 6CG7s, and elevate that potential . . . meaning
that the rectifier heater would also be at a higher potential, and the 6CG7
would consume an extra 0.6 amps.


You need two heater strings. Either a separate xfmr or a new one
wioth more windings.

Yes, that much is clear. I was just wondering if someone had figured out a
solution to this "problem" other than that. I guess I was wondering if the
"impossible" was possible . . . .

Jon

[Iain Churches[_2_]]

"Jon Yaeger" wrote in message
...
in article
,
Bret Ludwig at wrote on 12/3/07 3:54 PM:

On Dec 3, 2:30 pm, Jon Yaeger wrote:
In designing the Eico CF and trying to incorporate ideas from the group,
I
am wondering how it might be possible to elevate the heater potential
for
just the pair of cathode followers?

I know how to elevate the entire heater string, but I don't think that I
want to.

The transformer has a pair of 6.3 VAC filament windings - one side per
channel. It also has a 5V winding for the rectifier.

In bantering about some possibilities, I wonder if it would be a bad
idea to
use the 5V winding for the 6CG7s, and elevate that potential . . .
meaning
that the rectifier heater would also be at a higher potential, and the
6CG7
would consume an extra 0.6 amps.


You need two heater strings. Either a separate xfmr or a new one
wioth more windings.

Yes, that much is clear. I was just wondering if someone had figured out
a
solution to this "problem" other than that. I guess I was wondering if
the
"impossible" was possible . . . .


Hi Jon. I use a small separate xformer for the CF heater.

Iain

[John Byrns]

In article ,
Jon Yaeger wrote:

In designing the Eico CF and trying to incorporate ideas from the group, I
am wondering how it might be possible to elevate the heater potential for
just the pair of cathode followers?

I know how to elevate the entire heater string, but I don't think that I
want to.

The transformer has a pair of 6.3 VAC filament windings - one side per
channel. It also has a 5V winding for the rectifier.

In bantering about some possibilities, I wonder if it would be a bad idea to
use the 5V winding for the 6CG7s, and elevate that potential . . . meaning
that the rectifier heater would also be at a higher potential, and the 6CG7
would consume an extra 0.6 amps.

Ideas?

Yes, connecting the CF heater to the 5 VAC winding is a Bad Idea (tm)
and is likely to elevate the heater more than you want.

Why not use a grounded, or near ground, heater supply with the CF
cathode resistor feed from a negative supply? With the grid resistor
connected to ground this would put the cathode near ground potential.
There are several potential ways of building a negative supply, I would
probably first try a half wave voltage doubler connected to the bias
rectifier tap on the HV winding of the power transformer, unless the
voltage there is too low.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Mark S]

"Jon Yaeger" wrote in message
...
in article
,
Bret Ludwig at wrote on 12/3/07 3:54 PM:

On Dec 3, 2:30 pm, Jon Yaeger wrote:
In designing the Eico CF and trying to incorporate ideas from the group,
I
am wondering how it might be possible to elevate the heater potential
for
just the pair of cathode followers?

I know how to elevate the entire heater string, but I don't think that I
want to.

The transformer has a pair of 6.3 VAC filament windings - one side per
channel. It also has a 5V winding for the rectifier.

In bantering about some possibilities, I wonder if it would be a bad
idea to
use the 5V winding for the 6CG7s, and elevate that potential . . .
meaning
that the rectifier heater would also be at a higher potential, and the
6CG7
would consume an extra 0.6 amps.


You need two heater strings. Either a separate xfmr or a new one
wioth more windings.

Yes, that much is clear. I was just wondering if someone had figured out
a
solution to this "problem" other than that. I guess I was wondering if
the
"impossible" was possible . . . .

Jon


Hi Jon,
Wind your own little 1:1 6.3v isolation Xformer?
Mark

[Iain Churches[_2_]]

"John Byrns" wrote in message
...
In article ,
Jon Yaeger wrote:

In designing the Eico CF and trying to incorporate ideas from the group,
I
am wondering how it might be possible to elevate the heater potential for
just the pair of cathode followers?

I know how to elevate the entire heater string, but I don't think that I
want to.

The transformer has a pair of 6.3 VAC filament windings - one side per
channel. It also has a 5V winding for the rectifier.

In bantering about some possibilities, I wonder if it would be a bad idea
to
use the 5V winding for the 6CG7s, and elevate that potential . . .
meaning
that the rectifier heater would also be at a higher potential, and the
6CG7
would consume an extra 0.6 amps.

Ideas?

Yes, connecting the CF heater to the 5 VAC winding is a Bad Idea (tm)
and is likely to elevate the heater more than you want.

Why not use a grounded, or near ground, heater supply with the CF
cathode resistor feed from a negative supply? With the grid resistor
connected to ground this would put the cathode near ground potential.
There are several potential ways of building a negative supply, I would
probably first try a half wave voltage doubler connected to the bias
rectifier tap on the HV winding of the power transformer, unless the
voltage there is too low.


My simpler method is to use a separate xformer for
the heater, rectify for 6V3 DC but keep this supply
floating (no ground connection) I have 285V B+ available,
so I use 680k and 270k in series across this, to get 90V at
the junction (decoupled to ground with 0.1µF) and take
a feed from here to both sides of the floating heater
supply via 100 Ohm resistors.

Iain

Iain

[Patrick Turner]

Jon Yaeger wrote:

In designing the Eico CF and trying to incorporate ideas from the group, I
am wondering how it might be possible to elevate the heater potential for
just the pair of cathode followers?

I know how to elevate the entire heater string, but I don't think that I
want to.

The transformer has a pair of 6.3 VAC filament windings - one side per
channel. It also has a 5V winding for the rectifier.

In bantering about some possibilities, I wonder if it would be a bad idea to
use the 5V winding for the 6CG7s, and elevate that potential . . . meaning
that the rectifier heater would also be at a higher potential, and the 6CG7
would consume an extra 0.6 amps.

Ideas?

Thanks.

Jon

Install an extra filament tranny to do the job right.

The filament winding should have a CT and can be biased simply by a 220k
from the cathode of the CF.
But you also want 47uF to 0V to ensure signal from the mains doesn't get
into the cathode circuit.

Patrick Turnwe.

[John Byrns]

In article ,
"Iain Churches" wrote:

"John Byrns" wrote in message
...
In article ,
Jon Yaeger wrote:

In designing the Eico CF and trying to incorporate ideas from the group,
I
am wondering how it might be possible to elevate the heater potential for
just the pair of cathode followers?

I know how to elevate the entire heater string, but I don't think that I
want to.

The transformer has a pair of 6.3 VAC filament windings - one side per
channel. It also has a 5V winding for the rectifier.

In bantering about some possibilities, I wonder if it would be a bad idea
to
use the 5V winding for the 6CG7s, and elevate that potential . . .
meaning
that the rectifier heater would also be at a higher potential, and the
6CG7
would consume an extra 0.6 amps.

Ideas?

Yes, connecting the CF heater to the 5 VAC winding is a Bad Idea (tm)
and is likely to elevate the heater more than you want.

Why not use a grounded, or near ground, heater supply with the CF
cathode resistor feed from a negative supply? With the grid resistor
connected to ground this would put the cathode near ground potential.
There are several potential ways of building a negative supply, I would
probably first try a half wave voltage doubler connected to the bias
rectifier tap on the HV winding of the power transformer, unless the
voltage there is too low.


My simpler method is to use a separate xformer for
the heater, rectify for 6V3 DC but keep this supply
floating (no ground connection) I have 285V B+ available,
so I use 680k and 270k in series across this, to get 90V at
the junction (decoupled to ground with 0.1µF) and take
a feed from here to both sides of the floating heater
supply via 100 Ohm resistors.

It's not obvious to me that your method is simpler than mine, what with
your rectifier and all. I would agree that adding an unrectified heater
transformer is simpler in concept, although it can be difficult to find
space for it in some tightly packed old amps, I'm not familiar with the
2080 so it may well have enough space for an additional transformer.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

[Adam Stouffer]

Jon Yaeger wrote:


Ideas?

Thanks.

Jon


Leave them all float and bypass one side to ground with a cap if you
have hum problems.


Adam