[AMRadio] Viking II Audio Mod Question: Thanks

[Donald Chester]

A worthwhile mod I once made to a Ranger and to a Valiant was to take the DC 
off the driver transformer.  I used a 1 mf non-electrolytic capacitor 
between the plates of the triodes in parallel and the primary of the driver 
transformer.  I used a plate resistor 30K @ about 5 watts to carry the DC to 
the plate.  Since there is a big voltage drop in the plate resistor, I 
returned the resistor to the HV B+ instead of the LV B+, and the plate 
voltage on the driver tube was about normal.  This helped the audio 
enormously, as the DC really saturates that little transformer, resulting in 
loss of bass response and resultant phase shift distortion.

I then went a step further by removing and disassembling the driver 
transformer.  I restacked the laminations like a power transformer, 
alternating the directions of each adjacent E-I lamination assembly.  This 
eliminates the gap in the core, greatly increasing the inductance of the 
windings and results in still more improvement in low frequency response and 
power handling capability of the transformer without distortion.

Don K4KYV

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