KA7OEI built a battery pack to replace the obsolete “A/B” battery for Zenith TransOceanic (ZTO) H-500 and wrote a post on his blog detailing its assembly:
There are several things that I decided that this voltage converter should do:
- Automatically power up and shut down when the radio is turned on and then off
- Cause no interference to radio reception
- Consume minimal current when the radio is turned off
- Produce a regulated B+ voltage
- Regulate the filament voltage so that the radio functions properly even when the battery is mostly discharged so that maximum use can be made of its total capacity
While I was at it I decided that it should be able to do a few other things:
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- If the radio is on for a very long time (e.g. more than about 2 hours) do a “power save” shut down to (hopefully) prevent the batteries from being completely flattened
- “Lock out” the operation of the radio if the batteries are already extremely low. Avoidance of completely killing the battery may reduce the possibility of their leaking
