26-05-2013, 04:20 PM
Using the scope indicated immediately what the prob with the -24V was, the ripple was 50Hz, checking the bridge rectifier once it was out showed an O/C diode. Changed for 4 x1N4007, Perfect, All voltages correct after tweaking the pot. Listening to the radio and also with an external signal, one channel was slightly weaker and tinnier. Changing a few of the caps in the pre-amp / tone control section made no difference. Hard wire bridge between the channels pinpointed it to the final pre-stage. Voltage checks showed yet another 3 legged fuse. Substitution , Sorted !! It worked fairly well before due to the feedback circuit, the fault being like having a low value Emitter cap.
The FM frequency indication meter has become intermittent and sticky, I took it apart but could see no obvious problem. I still have the problem with the poor AM sensitivity at the aerial socket. This appears to be down to the MW I/P coil, probably some shorted turns, maybe in the future I will look into rewinding but for now this is as far as I go and It is definitely the last tranny job I do on old stuff.
Problems with the sliders being broken and missing, I will try and repair with carbon fibre inserts and maybe make a slider knob.
Anyway it's all back together and I will use it as my workshop radio etc.
Mike
The FM frequency indication meter has become intermittent and sticky, I took it apart but could see no obvious problem. I still have the problem with the poor AM sensitivity at the aerial socket. This appears to be down to the MW I/P coil, probably some shorted turns, maybe in the future I will look into rewinding but for now this is as far as I go and It is definitely the last tranny job I do on old stuff.
Problems with the sliders being broken and missing, I will try and repair with carbon fibre inserts and maybe make a slider knob.
Anyway it's all back together and I will use it as my workshop radio etc.
Mike
