Zenith TransOceanic Battery Project

Make it Portable, Rechargable, Efficient, Cheap

Many of the battery options for the Zenith T-O involve buying 6 D-Cells and 10 9-Volt batteries, or 60 AA cells. These struck me as expensive, inconvenient and wastful. There must be a better way. I've been tinkering with some Gel (Sealed, Lead-Acid or SLA) Battery chargers lately so I've been trying to find a way to put one into a Zenith T-O for use without wires - portable is a bit of a stretch, as heavy as it is.

Design Parameters

Tube Portables require two battery voltages:

  • B+ (HV Plate) - 90 volts, fairly well regulated, probably no more than 10ma, but possibly up to 20ma.
  • A+ (Filament) - 9 Volts, 250ma

For simplicity, it is desirable to pull both voltages from a single battery, and that battery be a) rechargable, b) large enough capacity for a reasonable run-time between charges, and c) commonly available. For the purpose of this project, 2x6V or a single 12V Gel battery will form the power source. Alternatively (for size requirements), could use 6 or 8 "D".

  1. Battery / Inverter should be rechargable; any charging mechanism would be external (for now!)
  2. Life - 5 to 20 hours continuous use (before recharge)
  3. Protection and Safety:
    1. Protect Outputs from exceeding nominal voltages (Protect the Antique Radio Circuitry)
    2. Protect the inverter's Gel battery from excessive discharge (Protect the Battery)
    3. Needs to be safe from overheating

Size and Appearance - should fit in the space formerly occupied by the Z-985 battery / covered to look like one of the available batteries from the era:

  1. Zenith Z-985
  2. Burgess G6B60
  3. Eveready 752
  4. Hallicrafters P999
  5. Ray-O-Vac AB995
  6. Sears 6401
  7. RCA VS047

The enclosure dimensions (including the Gel Battery, circuitry, 4-pin connector) must fit: 14-1/2" long x 4-1/2" wide x 2-1/2" high

Dry or Rechargable Batteries

Various projects are described for DIY or for commercial purchase that use multiple dry battery holders, and combinations of D-cell (1.5V) and 9-Volt batteries to achive the filament and HV power. Althought this is simple and straightforward, with a minimum of parts, this is not the direction this project is intended to take - either the inconvenience of recharging the cells or the ongoing cost of consumables (dry batteries).

Hans Borngräber's Inverter

This project was apparently to create a high-voltage from D-Cells designed to illuminate some Nixie tubes

  • Pro - Simple, low parts count, high efficiency (above 75%), transformerless
  • Con - actively regulated, but doesn't shut-off to protect battery.
AusBatt - simple 'electronic vibrator' supply

This was a project for a 67-volt battery for antique radios

  • Pro - Even Simpler, even fewer parts
  • Con - not actively regulated and cannot adjust for a falling battery voltage, uses an expensive transformer, a reported audible whine (from switching the transformer), apparently too large for placing inside the radio.
Good Implementation Notes and Ideas from these projects
  1. Diode after the inductor - might switch to a 'fast-recovery' type diode to eliminate or reduce switching peaks on output.
  2. Output Voltage Cleaning - basically a Pi-type filter:
    1. Include an inductor on output to smooth the voltage (560uh)
    2. Poss. Include 100V Zener for additional protection
    3. Additional 100uf/100V Cap after smoothing inductor
  3. Possible to sense when the 9V filament supply is switched to turn on the HV.
  4. Switch On relay could be a simple reed/DIP relay
  5. HV Sense pickup: 0.1uf in parallel to stabilize
  6. Sense battery power used by including .5 ohm resistor prior to switching inductor.
  7. Sense battery voltage on input; shutdown if < 11.5V
  8. Use a Push-Button starter - a PB temporarlity connects the relay coil, starting the circuit via the relay's DPST switch. If battery voltage is good, Arduino will hold the relay / if not, the relay won't be continued.
Getting Started
Results

Source Sketch Files

  • Version 1 - works with Arduino-0017, uses buttons to START and STOP the booster. Shuts down on around 11.2 battery voltage.

Research and Resources
<>Comparing and Contrasting the features of other publicly available projects.

Research into Pulse-Width Modulation (PWM), Switch-Mode Power Supply (SMPS), and Inductors.