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PJL · 17th Feb 2017, 10:26 pm

Ignore R45 and R46, they will be fine.

One PX4 is taking 23mA, the other only 8mA. What we need to do now is check the grid circuit to see if that is the cause.

With the power off measure the resistance of the PX4 grids to earth. They should both read around 101K. You did replace C45 amd C46?

If the resistance is OK, then switch on and measure the PX4 grid volts from chassis. This should be near zero.

If it is near zero then swap the PX4's and very carefully (dangerous voltages!) measure the voltage on R47 and R48 again and see if the higher voltage has swapped over. Also measure the voltage across R44 so we know the bias condition.

17th Feb 2017, 10:26 pm	#154
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Restore a Beau Decca Ignore R45 and R46, they will be fine. One PX4 is taking 23mA, the other only 8mA. What we need to do now is check the grid circuit to see if that is the cause. With the power off measure the resistance of the PX4 grids to earth. They should both read around 101K. You did replace C45 amd C46? If the resistance is OK, then switch on and measure the PX4 grid volts from chassis. This should be near zero. If it is near zero then swap the PX4's and very carefully (dangerous voltages!) measure the voltage on R47 and R48 again and see if the higher voltage has swapped over. Also measure the voltage across R44 so we know the bias condition.