15-02-2017, 05:59 PM
I have now cleared the final fault! 
With the full LT supply restored, as I said, it became stable again, but that was with the AGC capacitor shorted out. When I took the short off, it became partly unstable again if the HT was too high. Some final checking with the meter located a dry joint on one end of the V2 control grid decoupling capacitor (C7 0.1uF). As soon as this was made good, the set was fully stable on 220 Volts HT and the AGC operational (temporary short removed).
All that remains now is to rewire, and build a new PSU.
Bob
With the full LT supply restored, as I said, it became stable again, but that was with the AGC capacitor shorted out. When I took the short off, it became partly unstable again if the HT was too high. Some final checking with the meter located a dry joint on one end of the V2 control grid decoupling capacitor (C7 0.1uF). As soon as this was made good, the set was fully stable on 220 Volts HT and the AGC operational (temporary short removed).All that remains now is to rewire, and build a new PSU.
Bob
