Reply To: squeal when at high volumes

[Andy]

The currently available power transformers don’t supply what is called a “center tap”. That was a green/yellow wire in the instructions. The 100Ω resistors are there to create an artificial center tap. This is done by attaching a 100Ω resistor from each green filament line to ground. I usually attach it at the 2 pilot light terminals and ground it at the 3 pin ground terminal.

That is the first thing I would do as it is an important part of the circuit. This link has some more information: http://www.valvewizard.co.uk/heater.html