15-04-2020, 01:44 PM
Not getting much feedback from others on the forum, but I carry on. Perhaps all are bored with my restorations?
Narrowed the mains hum down to 50Hz pickup from the QMB mains switch on the back of the volume control. Switching the neutral instead of the line made no difference. Then I realised that the body of the control was not grounded, fitting a link wire to the chassis solved the hummmm. On inspection it seems that it is a replacement control, it must have hummed when it was first changed!
The shortwave oscillator core has set solid so refitted, and the set now picks up a few signals. It will need aligning. No idea what the frequency of the stations is or even what they are.
A new Y63 eye produces a good green glow but it is three quarters closed with no signal and only closes a bit more with a strong signal. Obviously the AGC has a problem, perhaps the decoupling capacitor and/or resistor needs replacing.
The crackles from the tuning spindle seem to be due to the coil and tuning subassembly to which it is attached being mounted on rubber insulators with one earthing wire to the main chassis rather than being mounted onto the main chassis.
I can't at present see a solution, I can't fit a spring grounding blade as that will ground the subchassis as well. It is obviously not meant to be solidly grounded otherwise the maker would not have gone to the trouble of building a separate panel.
Narrowed the mains hum down to 50Hz pickup from the QMB mains switch on the back of the volume control. Switching the neutral instead of the line made no difference. Then I realised that the body of the control was not grounded, fitting a link wire to the chassis solved the hummmm. On inspection it seems that it is a replacement control, it must have hummed when it was first changed!
The shortwave oscillator core has set solid so refitted, and the set now picks up a few signals. It will need aligning. No idea what the frequency of the stations is or even what they are.
A new Y63 eye produces a good green glow but it is three quarters closed with no signal and only closes a bit more with a strong signal. Obviously the AGC has a problem, perhaps the decoupling capacitor and/or resistor needs replacing.
The crackles from the tuning spindle seem to be due to the coil and tuning subassembly to which it is attached being mounted on rubber insulators with one earthing wire to the main chassis rather than being mounted onto the main chassis.
I can't at present see a solution, I can't fit a spring grounding blade as that will ground the subchassis as well. It is obviously not meant to be solidly grounded otherwise the maker would not have gone to the trouble of building a separate panel.
Boater Sam.
