K4040 Mains Transformer

I have had a K4040 for some years, all ok.

Have just moved house now I have fuse blowing and a valve failure. I have replaced these ok and all seemed well but the main fuse can blow at switch off. Mains transformer now buzzes did not notice this before. Have tested voltages around the amplifier and find the HT to be high at 455 volts (exceeding the capacitor voltage).

I have measured the incoming ac voltage at 247v. The mains transformer does not have the 245 volt tapping on the input, 230v being the highest.

The board is an issue 1 so no link position for a 245v tap .

Is the high voltage the source of my problem? If so can I obtain the new spec transformer?

Seems to me your battery of your multimeter is almost dead. Test with another multimeter or with a new battery inserted in your multimeter. If you really have an incoming 247 V AC, you will have problems with other devices in the future too.

Yes the voltage is as measured (multimeter checked) 247v AC. Apparently quite normal for the UK.

The latest K4040 circuit now shows a 245v tapping on the mains primary, mine has 230v only, perhaps this is the reason?

My supply voltage with the 230v tapping is about 7.5% high so putting the HT voltage at 7.5% high, which is pretty much where it is.

Running the amp for a prolonged time will certainly lead to wear on all HT parts.
Possible solutions:
Get an external step-down or variac transformer. Sometimes they can be found cheap.
Get a K4040 transformer with 245V primary (order code TR4040). Careful: Velleman distributors do not stock this item, they have to order it for you.