[AMRadio] Ranger Audio... the numbers

Jack Schmidling jack at schmidling.com
Fri Nov 17 10:45:28 EST 2006

Gary Schafer wrote:

> Check at the center tap of the mod driver transformer with your scope and
> see if you see anything there. Could be a bad or missing bypass cap there.

It's brand new but I didn't have a 15mf so I used a 47mf.. ditto for C59A.

> Check the jumpers on the plug in the back to be sure that the proper taps on
> the mod transformer are selected.

All ok.

> Check the clamp tube circuit. Could be holding the screen slightly low on
> the 6146 and clipping the modulation peaks to the screen.

Screen voltage is 150 and the nom is 190.

However, R35, the Modulator Screen Voltage Adjustment resistor seems to 
go to the clamp circuit and it is not at all clear what is going on 
here.  It seems to me that diddling with it changes the screen voltage 
on the 6146.

So does diddling with the modulator current effect the 6146 screen 
voltage or do I have a screen voltage problem?

> Check modulator screen voltage.

It is the nominal 250V... but again, why is it nominal if that resistor 
is there to diddle with the current?


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