04-09-2025, 06:25 PM
You could well be correct about that - I don't have the experience to know for sure either way - but there's two things that I wonder. The first I've already mentioned - how noticeable/objectionable would the resulting distortion be given the performance of the audio sections of the set? The second is something I've been thinking about over the course of the afternoon:
For a transistor in a conventional class A audio circuit with a resistive load, when it is conducting for something less than 360 degrees, it's easy to visualise the waveform and understand where the distortion is coming from. But doesn't this change when the collector load is inductive? In that case, the cycle is completed with the energy stored in the inductance. At least, that's what I seem to recall from learning about transmitters many moons ago.
As mentioned, I can't say either way, but it's something I'd be keen to investigate if I had the set in front of me. I don't stray too far from AF all that often, but it's good to occasionally learn something new...
I suppose if TR2 was cut off too much, the resulting loss of signal might cause the AGC voltage to drop back a bit, meaning that there might well be an upper limit to the extent to which TR2 can be biased off before a kind of equilibrium is reached? That's another interesting line of enquiry.
Some sets had an additional damping diode to cope with gross overloads, but those seemed to fall out of favour fairly early on - at least for Hacker sets
There's often rather more to "simple" circuits than meets the eye, and it can be good fun to peel back the layers!
For a transistor in a conventional class A audio circuit with a resistive load, when it is conducting for something less than 360 degrees, it's easy to visualise the waveform and understand where the distortion is coming from. But doesn't this change when the collector load is inductive? In that case, the cycle is completed with the energy stored in the inductance. At least, that's what I seem to recall from learning about transmitters many moons ago.
As mentioned, I can't say either way, but it's something I'd be keen to investigate if I had the set in front of me. I don't stray too far from AF all that often, but it's good to occasionally learn something new...
I suppose if TR2 was cut off too much, the resulting loss of signal might cause the AGC voltage to drop back a bit, meaning that there might well be an upper limit to the extent to which TR2 can be biased off before a kind of equilibrium is reached? That's another interesting line of enquiry.
Some sets had an additional damping diode to cope with gross overloads, but those seemed to fall out of favour fairly early on - at least for Hacker sets
There's often rather more to "simple" circuits than meets the eye, and it can be good fun to peel back the layers!
