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Battery Boxes
Here are what powers my tube radios. The box on the right
supplies 1.5 and 3 volts for the filaments using two D cells in series. The B+
supply is ten 9 volt batteries tapped at the half way point for a 45 and 90
volt supply.
There are binding post type terminals
on the front panel for the connections but in addition
to those, I use a single small 6 pin molex type connector to quickly connect
power to my radios. All my connections are standardized. I can use either of the battery
boxes to power any of my little sets. Using the little connectors prevents making
a wrong connection to a radio and frying something. That is about all that
I can say about the box on the right. I have had it for a year and it has worked
out well for me. But it was time I switched to rechargeable batteries. Buying
ten 9 volt batteries at a clip just isn't within my budget anymore.
My rechargeable supply consists of ten 8.4 NiMH batteries. I bought
the batteries on an ebay deal. The battery holders
are offered in a limited quantities at my web store as well as the binding posts.
The filament supply is provided by two 2 volt lead acid batteries.
At the 2 volt tap, I used a 3 amp silicon power diode to drop .6 volts to give
me 1.4 volts. At the 4 volt tap, I used two silicon diodes so I would end up
with 2.8 volts. The voltages don't end up exact, but they are close enough to
light the tubes. The terminals on the front are labeled: 0, 1.4, 2.0, 2.8 and
4.0.
The B+ batteries are tapped at 3, 5, 8 and 10 batteries.
This gives 22.5, 45, 67.5 and 90 volts, or close to those voltages.
There is no common ground between the A and B battery supplies.
The charger consists of a little power supply that I had built to
power my pentaflex radio. It provides 6 volts
AC and 150 volts DC. I used a 4 pin connector as a standardized connector for
my AC operated radios. I put a mating connector on my battery box for charging
the cells. The 6 volts AC had to be rectified and a current limiting resistor
added, and the B battery supply only needed a current limiting resistor.
 Here is the schematic of the charger that I am using. This is
actually the power supply for my pentaflex radio.
Until now I have just shown you battery operated sets. These are pretty safe to use,
perhaps a little tingle if you got the fingers across the 45 volt supply. Now we are
in the big leagues where safety becomes important. So here's the word. If you build
this, take it to someone that knows something about electronic safety and get it
checked out before you plug it in. Once it is checked out, you still have to be
careful using this.
 This is the battery box schematic.
These cells are charged using a 6800 ohm current
limiting resistor. The current flow is 9 ma, way below the 15 ma maximum value.
The filament supply is made up of two 2 volt cyclon batteries.
The charging circuit supplies around 280 ma which
is also way below the maximum current value of the battery.
To wrap this all up, the main points are to make standardized
connectors to power all your radios and using rechargeable batteries will give
you many more hours of listening pleasure without extra expense. Take a look
at the pictures and if you have questions, my e-mail is available. Good luck ~ Dave, N2DS
Here is my battery box in action. The radio is my Philco 40-88
battery only set. The filament supply is 1.5 volts to light up 4 tubes (5 on shortwave).
90 volts is required for the plate supply. The radio plays well with this and there
is no hum if the charger is left plugged in.
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