19-11-2015, 05:34 PM
(19-11-2015, 02:52 PM)Refugee Wrote: I doubt the aerial tuning would affect the mixer that much because the output impedance will only change very little as it is adjusted.
It is just a stand alone unit between the aerial socket and the mixer.
I'll keep you informed. I tend to have my own weird and wacky way of dealing with such issues, given I tend to use the situation in itself as a learning exercise. So, I'm looking into the whole Local Oscillator and Mixer circuit both on this set and how it also relates to other sets. Sor t of bang in a bit of theory with an actual set to relate to.
The schematic on this set does show a very heavy going meshwork of switches and coils with trimmers and padders and so forth. HMV went to town on this in a big way. There is even a gram switch and speaker "off" switch apart from the multiple trimmer switches and even image rejection switch and so on and so on.
All the suggestion here will be included in my work. I'll be checking there is indeed a decent aerial feed to the grid and also any HF caps and so on. As well as the rotary switches which are pretty grim even after cleaning some weeks ago.
I did think maybe the Mixer tube was suspect but now feel almost certain I'm looking at worn and tired circuit connections. Given every single scale lamp is dead and O/C, you can see most of what is wrong is down to ravages of time.
P.S. thanks for all your positive comments in the course of this thread
