[Station X]

I would suggest that there are lessons for us all here:-

1. Specify which service sheet is being used at the very beginning and stick to it. This would have prevented the needless changing of a 330pF capacitor in the mistaken belief that it was the audio coupling capacitor.

Personally I use the manufacturers service sheet if there is one, but I appreciate that Trader sheets seem to be more widely available. Also those offering assistance may not have the same service sheet as is being used by the OP.

2. Make sure that the OP has reliable test equipment and is using it correctly. In the case of a test meter this means using the correct sockets for the test leads, selecting the appropriate function such as AC or DC Volts and selecting a range suitable for the expected result. If necessary switch down the ranges until a sensible reading is obtained.

Had the voltage readings been correct, we wouldn't have suspected a mains transformer fault.

3. Only change one component at a time and make tests after doing so. It is likely that if just the audio coupling capacitor had been changed and then the set was powered up via a test lamp then, once the faulty mains switch had been sorted, HT would have been present. The smoothing caps could then have been changed, preferably one at a time, rechecking the HT after each change. This would have immediately have showed up the missing connection to the centre tap of the HT winding.

4. If test results are not as expected, the do the test again using different test points. We had assumed that there was a connection from the HT winding centre tap to the chassis, albeit via bias resistors in this case. A voltage test from the centre tap to HT positive would have shown that this was not the case, as would a resistance check from the centre tap to the chassis.

I realise that I am saying this with the benefit of hindsight. I also intend no criticism of the OP.