I had a go at doing a full realignment according to the instructions in the service manual.
It was not easy, mainly made difficult by the drawing of the layout above chassis being wrong, well it is for the KB 444 so it may be correct for that radio but it is definitely wrong for this one.
I can confirm all the component values of the KB 402 and layout positions under the chassis are identical to the KB 402 and the above chassis drawing is correct except they have labelled the trimmers on the tuning capacitor incorrectly.
If you look at the drawing and the layout of the aerial, bandpass and oscillator coils the layout dictates which is the obvious way to connect to each section of the tuning capacitor.
e.e. The Aerial coil is on the bottom left of the drawing, and this connects to the tuning cap section immediately to the right, labelled incorrectly as the oscillator. The bandpass coil connects to the middle section of the tuning cap, labelled correctly. The Oscillator coil, top centre of the drawing, connects to the rear section of the tuning cap, labelled incorrectly as Aerial.
Well done KB! I cant see it being any different on the actual KB 444 radio as it is so logical and natural to wire it this way.
Anyway I did the full realignment setting first the IF to 130kHz then doing the MW and LW RF alignment. It was difficult as performance had deteriorated on MW and LW, so I went back and peaked the IF trimmers for best reception on MW. Low and behold for best performance on MW and LW the IF frequency had moved back to 120kHz, so I wonder if that is another mistake in the service manual.
It was worth a try, thanks for all your help and advice.
Lawrence, I can confirm this circuit is weird and different, but the radio does work well, at least from the point of view of sensitivity. But there is a little distortion on some stations which improves if the Local-Distant switch is switched to local. This adds a very small value (twisted enamelled wire) capacitor in series with the aerial.
This circuit appears not to have any proper AGC.
Mike
It was not easy, mainly made difficult by the drawing of the layout above chassis being wrong, well it is for the KB 444 so it may be correct for that radio but it is definitely wrong for this one.
I can confirm all the component values of the KB 402 and layout positions under the chassis are identical to the KB 402 and the above chassis drawing is correct except they have labelled the trimmers on the tuning capacitor incorrectly.
If you look at the drawing and the layout of the aerial, bandpass and oscillator coils the layout dictates which is the obvious way to connect to each section of the tuning capacitor.
e.e. The Aerial coil is on the bottom left of the drawing, and this connects to the tuning cap section immediately to the right, labelled incorrectly as the oscillator. The bandpass coil connects to the middle section of the tuning cap, labelled correctly. The Oscillator coil, top centre of the drawing, connects to the rear section of the tuning cap, labelled incorrectly as Aerial.
Well done KB! I cant see it being any different on the actual KB 444 radio as it is so logical and natural to wire it this way.
Anyway I did the full realignment setting first the IF to 130kHz then doing the MW and LW RF alignment. It was difficult as performance had deteriorated on MW and LW, so I went back and peaked the IF trimmers for best reception on MW. Low and behold for best performance on MW and LW the IF frequency had moved back to 120kHz, so I wonder if that is another mistake in the service manual.
It was worth a try, thanks for all your help and advice.
Lawrence, I can confirm this circuit is weird and different, but the radio does work well, at least from the point of view of sensitivity. But there is a little distortion on some stations which improves if the Local-Distant switch is switched to local. This adds a very small value (twisted enamelled wire) capacitor in series with the aerial.
This circuit appears not to have any proper AGC.
Mike
