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.
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".
- Battery / Inverter should be rechargable; any charging mechanism would be external (for now!)
- Life - 5 to 20 hours continuous use (before recharge)
- Protection and Safety:
- Protect Outputs from exceeding nominal voltages (Protect the Antique Radio Circuitry)
- Protect the inverter's Gel battery from excessive discharge (Protect the Battery)
- 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:
- Zenith Z-985
- Burgess G6B60
- Eveready 752
- Hallicrafters P999
- Ray-O-Vac AB995
- Sears 6401
- 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
- Diode after the inductor - might switch to a 'fast-recovery' type diode to eliminate or reduce switching peaks on output.
- Output Voltage Cleaning - basically a Pi-type filter:
- Include an inductor on output to smooth the voltage (560uh)
- Poss. Include 100V Zener for additional protection
- Additional 100uf/100V Cap after smoothing inductor
- Possible to sense when the 9V filament supply is switched to turn on the HV.
- Switch On relay could be a simple reed/DIP relay
- HV Sense pickup: 0.1uf in parallel to stabilize
- Sense battery power used by including .5 ohm resistor prior to switching inductor.
- Sense battery voltage on input; shutdown if < 11.5V
- 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.
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.
- www.batpack.com Sells a very nice battery pack
- Roberts Radios, UK. Nice source of battery pack scans
- Repro Boxes, Labels, Connectors for the T-O
- Hans Borngräber translated version of Han's inverter
- Ausbatt B-Battery using a transformer step-up, from Australian magazine
- Zenopac Battery Pack Another commercial battery pack
Research into Pulse-Width Modulation (PWM), Switch-Mode Power Supply (SMPS), and Inductors.