Tag Archives: Hacks

An A/B battery replacement for the Zenith TransOceanic H-500 radio with filament regulation

via Dangerous Prototypes


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:

  • 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

LiPo batteries hacking and refurbishing

via Dangerous Prototypes


Karman wrote an article showing how to refurbish dead batteries to extend its life:

One of the difficult parts when prototyping is to find reliable power sources. Today is still hard to find the battery size we want to use because country exporting frontiers stops these chemical packages. Here I’ll show how to refurbish dead batteries by combining cells and protection circuits to preserve battery life.
An (almost) dead Apple MacBook Pro (17″) battery fell in my hands so I decided to tear it down to see if there was something profitable. Inside I found that the battery pack was composed with 6 individual cells, paired in 3 groups.

More details at Karman’s blog.

A simple push-pull audio amplifier using russian rod tubes and power transformers

via Dangerous Prototypes


KA7OEI blogged about a simple push-pull audio amplifier using russian rod tubes and power transformers:

Many years ago I’d read about the type of tube that is now often referred to as a “Gammatron” – a “gridless” amplifier tube of the 1920s, so-designed to get around patents that included what would seem to be fundamental aspects of any tube such as the control grid.  Instead of a grid, the “third” control element was located near the “cathode” and “anode”.  As you might expect, the effective gain of this type of tube was rather low, but it did work, even though it really didn’t catch on.  It was the similarity between the description of the “Gammatron” and these “rod” tubes that intrigued me.

More details at KA7OEI’s blog.

Hacking your mouse for rapid firing

via Dangerous Prototypes


Kerry Wong has written an article detailing a simple hardware hack to make your mouse capable of doing rapid firing:

In this blog post, I will show you a simple hardware hack to make your mouse capable of rapid firing (or automatic continuous clicking). Of course you can always resort to software mods to achieve the same goal, but admittedly doing so in hardware is nevertheless more fun and as a bonus you also get an extra button. A video demonstrating this hack can be found towards the end.
For a typical mouse, whenever a button is clicked the output voltage level from the button changes between high (e.g. Vcc) and low (e.g. Ground) and this voltage level is in turn translated into the clicks. So the idea behind this hack is simple, if we could connect a circuit in parallel to the mouse button and automatically change the output voltage level we would essentially achieve the same effect as physically clicking the button.

More details at Kerry Wong’s blog.

Check out the video after the break.

Nuclear physic applied in smoke detectors

via Dangerous Prototypes


Robert Gawron writes:

Not many people know, but in some smoke detectors, radioactive materials play an essential role. Today I will present one of those devices, and my -successful- attempt to reverse engineer it and get the circuit diagram.
Those smoke detectors uses a small amount of Americium-241 (chemical symbol: Am) obtained in nuclear reactors as a decay product of Plutonium-241. Am241 emits mainly alpha particles, but also some gamma rays. In smoke detectors it is in a form of an oxide Am02.

More details at Robert Gawron’s blog.