Bias Cells

11/24/2011 5:50:09 PMMitch

Hello all,

For those who have not seen these bias cells before, i hope that my pics are correct and provide information.

I have seen posts about putting them in boiling water to rejuvinate them, then seal them after they dry.

Mine reads 0.5 VDC with the radio operating, i am going to try to get it back to 1 VDC.

Other input is appreciated to help others.

Mitch

11/24/2011 5:54:49 PMMitch

:Hello all,
:
:For those who have not seen these bias cells before, i hope that my pics are correct and provide information.
:
:I have seen posts about putting them in boiling water to rejuvinate them, then seal them after they dry.
:
:Mine reads 0.5 VDC with the radio operating, i am going to try to get it back to 1 VDC.
:
:Other input is appreciated to help others.
:
:Mitch
:
:

:
:

:
Another picture.

11/24/2011 7:56:28 PMNorm Leal

Hi Mitch

Nice photos.

In many cases you don't need the bias cell. Often these cells are biasing a 1st audio amplifier like #75 tube. Later radios didn't add bias on this stage. Just a straight connection and high value grid resistor, 4.7 or 10 meg.

Best to short across the bias cell but don't leave a bad one in the circuit. Open it will cause problems.

Norm

::Hello all,
::
::For those who have not seen these bias cells before, i hope that my pics are correct and provide information.
::
::I have seen posts about putting them in boiling water to rejuvinate them, then seal them after they dry.
::
::Mine reads 0.5 VDC with the radio operating, i am going to try to get it back to 1 VDC.
::
::Other input is appreciated to help others.
::
::Mitch
::
::
::
::
::
:Another picture.
:
:
:

11/24/2011 11:52:43 PMWarren

This little bias cell is a nostalgia piece of radio history. Someone thought it was a good idea. It’s cool to have the original keep going. There is some insignificant advantage to have it in circuit.

11/26/2011 5:39:34 PMEdd

Sir Mitch . . . . .

Here is some additional info . . . as per their technical aspect . . . to be supplementing your submitted photos:

73's de Edd

There's one finite line between fishing . . . . . . and standing on the shore looking like an idiot.

:This little bias cell is a nostalgia piece of radio history. Someone thought it was a good idea. It’s cool to have the original keep going. There is some insignificant advantage to have it in circuit.
:

11/26/2011 7:34:13 PMDoug Criner

Their purpose was to reduce the plate current of the amp stage.

11/27/2011 11:49:21 AMAnthony Bitetto

I have a GE 250 that without this cell (four in series) my radio draws much more plate current, and plays low and distorted. I improvised a 6v battery from Radio Shack to stand in, and kept the individual cells and their cardboard tube with the hope of rejuvinating them some day.

Tony

1/2/2012 3:01:41 PMMitch to Brian C

:I have a GE 250 that without this cell (four in series) my radio draws much more plate current, and plays low and distorted. I improvised a 6v battery from Radio Shack to stand in, and kept the individual cells and their cardboard tube with the hope of rejuvinating them some day.
:
:Tony
:
Brian,

Is if this is what you have.

Mitch

1/2/2012 3:08:20 PMBrianC

::
:Brian,
:
:Is if this is what you have.
:
:Mitch
:
Looks like what I have...Could I use a modern button battery if I could find the voltage needed?

1/2/2012 3:15:27 PMMitch

:::
::Brian,
::
::Is if this is what you have.
::
::Mitch
::
:Looks like what I have...Could I use a modern button battery if I could find the voltage needed?
:
Brian,

Yes you can use a button battery, Bias Cells are rated at 1 to 1.5 VDC. Be careful on the polarity.

Or you can remove them and drop them into a cup of boiled water and wait for the small bubbles to stop, then dry them and measure the voltage, they should then last another 30 to 40 years.

Mitch

1/2/2012 3:44:34 PMWarren

Just to clarify the hot water trick. Boil a cup of water. Drop the cells into the hot water. You will see little bubbles escape the cell. Let the water cool off to room temperature.
The cell will suck water back into it. Dry the cell, and seal the carbon disk edges where it meets the metal edge. Careful not to get glue in the middle contact area. The cell is now rejuvenated.

1/2/2012 10:55:26 PMBrianC

Thanks for the info...When you say 'dry the cell'...just pat it dry, or some other drying method? Any particular glue to seal it?

1/2/2012 11:36:41 PMMitch

:Thanks for the info...When you say 'dry the cell'...just pat it dry, or some other drying method? Any particular glue to seal it?
:
Brian,

I just pat it down with a paper towel, let it air dry for an hour, then apply a thin bead of elmers glue to the edge and let it dry. What you do not want is the water leaking out.

Measure the voltage with a digital volt meter to assure polarity for at least 1 volt DC. Then re install the Bias Cells.

You will have kept the radio original in doing this and acheived some self satisfaction in your accomplishment and not with button batteries.

Mitch

1/3/2012 12:12:25 AMWarren

Have used super glue. apply with a toothpick carefully just around the edges.