02-12-2021, 06:04 PM
Now this screen is not earthed at either end. The manufacturer's diagram is correct providing that the screen is not connected to the IF transformer or the metal body of the volume control. It is not clear in the circuit diagram. The incorrect ground link from the pot earthy end to the metal body has been removed enabling the cathodes to receive bias. The braid is now as per the diagram the link from the cathodes to the volume control track bottom end.
The screen is connected as shown to the cathodes of V4 and V5. I am wondering if the capacitance of the short screened cable plays some part in a feedback route to the cathode. I have never seen this before.
Further work on this set shows that every tubular wax capacitor is beyond use. They are all TCC caps. I did find that the modulation suppressor across the mains had been disconnected at one end. It has been replaced with an X2 cap. This is the only signs other than a new mains lead of any previous repairs to this set.
All the said caps have been replaced with modern film caps, its not a rare set and there is no point in restuffing the caps with more expensive poly caps.
It now works very well subject to the usual poor performance of the inside out Celestion loudspeaker. I have never found one of these that sounds as well as a conventional one.
One small crack in the top of the front case, where the handle is, has been repaired with superglue and a backing plastic re-enforcement glued inside. This repair will be almost invisible when the case is polished.
The screen is connected as shown to the cathodes of V4 and V5. I am wondering if the capacitance of the short screened cable plays some part in a feedback route to the cathode. I have never seen this before.
Further work on this set shows that every tubular wax capacitor is beyond use. They are all TCC caps. I did find that the modulation suppressor across the mains had been disconnected at one end. It has been replaced with an X2 cap. This is the only signs other than a new mains lead of any previous repairs to this set.
All the said caps have been replaced with modern film caps, its not a rare set and there is no point in restuffing the caps with more expensive poly caps.
It now works very well subject to the usual poor performance of the inside out Celestion loudspeaker. I have never found one of these that sounds as well as a conventional one.
One small crack in the top of the front case, where the handle is, has been repaired with superglue and a backing plastic re-enforcement glued inside. This repair will be almost invisible when the case is polished.
Boater Sam.
