[AMRadio] Bias Battery

Bill Fizette w2dgb at ptd.net
Sun Nov 8 06:15:19 EST 2009

Radio Shack listed them about a year or so ago under camera items.  My local 
store didn't have one, but I ordered one, paid them, and it arrived in the 
mail in a few days from their central warehouse.  Cost was reasonable, and 
no charge for postage.  I was pleasantly surprised.  I have it in my WRL 
If you can't find the item, I probably still have the paper work here with 
the order number.

Another approach which you allude to is to tap off the filament supply with 
a simple doubler/rectifier/filter circuit.  Also, someone told me that he 
used a small transistor audio transformer in his AF67 to get the low 
voltage...then as above.  I have not tried either, but they are simple 

Bill   w2dgb

----- Original Message ----- 
From: "Jim Wilhite" <w5jo at brightok.net>
To: "AM Radio Discussion List" <amradio at mailman.qth.net>
Sent: Saturday, November 07, 2009 8:31 PM
Subject: [AMRadio] Bias Battery

>A long time ago I remember someone or several someones talking abut the
> modulator tubes bias battery in the AF 67/68.  It is a 22.5 volt battery
> that I am going to need.  I don't recall if the discussion turned into
> how to get the needed voltage from something in the radio or the battery
> is still available.
> Can someone enlighten me on the subject?  If the battery is available,
> where?  If a modification was performed, how, and where can I get a
> copy?  Or are both solutions plausible?
> TNX & 73
> Jim/W5JO
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