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Battery Boxes For Small Tube Radios

Battery Boxes: Left - Rechargeable, Right - Alkaline Cells

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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.


Rechargable Battery Box & Charger

Wiring View

Rechargeable Battery Box and Charger Wiring View

Rechargable Battery Supply Schematic

Battery Box Charger Schematic

Rechargable Battery Box Schematic charger Schematic

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. Good luck with your battery box. ~ Dave, N2DS

Battery Box and portable radio

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.