I managed to control the transistor overheating issue today by
using an Ac to Dc wall adapter. It outputs 6 volts, and works almost
as well as a 12v battery, but without the transistor going up in smoke
and catching on fire. Maybe that's what they mean by kacher...
Aye, those hot transistor problems can be very difficult to diagnose
and cure without an oscillocope.
In order for the transistor to operate efficiently with the higher input
voltage it is necessary to adjust the biasing to assure that it functions
as a Class C (or preferably Class E) power amplifier. Unfortunately most
simple regenerative oscillator circuits will function Class AB or B which
means that they'll run hot when the input voltage is upped.
With a scope it's possible to analyze the operational mode and add
certain components to "tune" the transistor for maximum output signal
while keeping it in the highly efficient Class C mode with narrow driving
pulses.
Without a scope there are things which may be done too. I'll see if I can
find some simple diagrams to make the point.
In the meantime, as you've verified, reducing the input voltage always works.
The Wiki article provides a good explanation.A page with some "tricks."The other two pages are cool too - links at the top of the page.
The diagram above shows how "self-bias" can be added to a
transistor hookup between the Emitter and Gnd. The resistor
may range from about 47 Ohms to several hundred ohms
depending upon the voltage powering the circuit. The Capacitor
is typically about 0.01 uF to 0.22 uF for RF circuits.
The self bias will work to stabilize transistor operation when
the circuit is powered over a range of voltages; the input supply
voltage may be reasonably increased without hazarding the
transistor. Self biasing will tend to limit current pulses to a
fairly safe range.
For there is nothing hidden that will not be disclosed, and nothing concealed that will not be known or brought out into the open.
Author
Topic: Woopy's kacher device... progress? (Read 39609 times)
