I'm working on a Philco 660 console chassis for which I have no speaker. For a test run following recapping,
I used a 10W 1.2K resistor in place of the field coil and a junk box transformer and speaker. Works, but sounds terrible. I've been looking for a correct replacement output transformer and have hit my knowledge limit. The 660 uses two 42 output tubes in push-pull configuration. Consulting a tube manual shows me that the plate impedance of a 42 is 10000 ohms. Do I need a xformer that has that impedance on each side of the input center tap or 10000 ohms total? Radio Daze has a decent selection of new xformers but I don't want to get one that won't give the best sound. I will probably get a new 4 ohm speaker to use with this set.

Hi Dave

You have done a good job investigating.. Push-pull 42's use a 10,000 ohm impedance transformer plate to plate. So that means 10,000 ohm total for the primary.

Norm

:I'm working on a Philco 660 console chassis for which I have no speaker. For a test run following recapping,
:I used a 10W 1.2K resistor in place of the field coil and a junk box transformer and speaker. Works, but sounds terrible. I've been looking for a correct replacement output transformer and have hit my knowledge limit. The 660 uses two 42 output tubes in push-pull configuration. Consulting a tube manual shows me that the plate impedance of a 42 is 10000 ohms. Do I need a xformer that has that impedance on each side of the input center tap or 10000 ohms total? Radio Daze has a decent selection of new xformers but I don't want to get one that won't give the best sound. I will probably get a new 4 ohm speaker to use with this set.

Thanks, Norm for the quick response. I'll order a new xfmr tonight

:Hi Dave
:
: You have done a good job investigating.. Push-pull 42's use a 10,000 ohm impedance transformer plate to plate. So that means 10,000 ohm total for the primary.
:
:Norm
:
::I'm working on a Philco 660 console chassis for which I have no speaker. For a test run following recapping,
::I used a 10W 1.2K resistor in place of the field coil and a junk box transformer and speaker. Works, but sounds terrible. I've been looking for a correct replacement output transformer and have hit my knowledge limit. The 660 uses two 42 output tubes in push-pull configuration. Consulting a tube manual shows me that the plate impedance of a 42 is 10000 ohms. Do I need a xformer that has that impedance on each side of the input center tap or 10000 ohms total? Radio Daze has a decent selection of new xformers but I don't want to get one that won't give the best sound. I will probably get a new 4 ohm speaker to use with this set.

Besides getting the correct output transformer, also check all your bias voltages, and make sure that both your output valves are working. With push-pull output circuits, it is often preferable to have a matched set of valves. Check for emision before blaming anything else. An HT check of course is the starting point of your diagnosis.

Anton