Home  Resources  References  Tubes  Forums  Links  Support 
Philco 38-116 revisited. Input transformer replacement
11/15/2004 10:25:24 AMDave Froehlich
Hello All,
The original input transformer had an open primary. The currently available replacement ends up overloading the inputs to the 6L6s. So what I intend to do is add an attenuating resistor.
One end of each of the secondaries is connected directly to a 6L6 grid.
The other ends of the secondaries is connected to a voltage divider. So this method may not work. See, the original transformer was a step down transformer. The new one steps up the signal, causing the output to distort. So what should I do? The new transformer is a Hammond 124E. How can I maintain the correct DC voltage to the grids of the 6L6s and attenuate the audio signal going to it? Maybe I have to replace some of the other resistors so that this transformer will work the way it is. Anyway the schematic is on this website.

Please help.

Thanks,

Dave...

11/15/2004 12:59:03 PMDave Froehlich
Hello Again,
I studied the schematic again and I didn't see any inverter tube for the push pull output. (Where is the inverter tube? I thought). So I had to reverse (invert) on one of the secondaries (duh! That is in place of the inverter tube.) and voila, problem solved. It can push-and-pull now instead of push and push or pull and pull. It wasn't a big problem after all.
Now I notice that the speaker doesn't sound too good at low volume. Better than sounding bad at loud volume. It has some tears. But it seems that the problem is in the gap, or it really is distortion a low volume. Solving that should solve all the electronic problems.

Dave...
:Hello All,
: The original input transformer had an open primary. The currently available replacement ends up overloading the inputs to the 6L6s. So what I intend to do is add an attenuating resistor.
:One end of each of the secondaries is connected directly to a 6L6 grid.
: The other ends of the secondaries is connected to a voltage divider. So this method may not work. See, the original transformer was a step down transformer. The new one steps up the signal, causing the output to distort. So what should I do? The new transformer is a Hammond 124E. How can I maintain the correct DC voltage to the grids of the 6L6s and attenuate the audio signal going to it? Maybe I have to replace some of the other resistors so that this transformer will work the way it is. Anyway the schematic is on this website.
:
: Please help.
:
:Thanks,
:
:Dave...



© 1989-2025, Nostalgia Air