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38-116 distortion
#1

Seeking some assistance with the 116....again......

It is currently playing on all 5 bands and has a tremendous sensitivity on all 5! Having come this far, my only remaining frustration is a bit of distortion. I had hoped that having the speaker reconed would solve the problem. It did NOT.

All resistors and caps have been changed along with bad wiring. The chassis was aligned with a signal generator per specs. Now working with the following voltages:

Plate voltage 6L6 is supposed to be 290, I'm running 324, pin 4 (S) is supposed to be 300, I'm running 335. Bias is -22.5. At the 6R7, I'm supposed to have 70v, and I have 85V. All other voltages in the radio seem to be on target.

Surprising today, having failed to put both 6L6 tubes in the chassis, it fired right up on one 6L6 and sounds GREAT....adding the second 6L6 brings the distortion. The result is the same regardless of which 6L6 is removed from the circuit. Sounds great with ONE but not BOTH power tubes. Do I have an issue with my output transformer? The resistance is all "good"....the field coil and output transformer all have the correct voltages.

I'm at a loss....any advice?

Thanks!
#2

Any chance someone reversed one of the windings of the phase inverting transformer? Are all resistors checked out past the phase inverting transformer? This seems a little wierd.
#3

Is the inverting transformer the input transformer? if so, a new one was put in however I am not the one who installed it and I have no clue if it is wired correctly. It is supposed to be equivilent to an original. As far as the resistors go, all resisitors have been checked and changed in the radio.

bm
#4

AGAIN!!!
Just kidding my friend. Well if you had a signal generator with tone modulation and a Oscope you could go hunting for it. If you need an output transformer I've got one. Just PM me.
Terry

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#5

I need more Advil !!!!!!!!!!!


bm
#6

Yes we are talking about the same transformer feeding the 6L6 output tubes. It is a phase inverter feeding the push-pull outputs. Try reversing one of the secondary windings connections. If that clears it up, you're done. If not, put it back the way it was and reverse the other secondary winding connections.

Let us know it that does it.

Schematic here:
http://www.nostalgiaair.org/PagesByModel...013234.pdf
#7

will try this evening

thanks!!
bm
#8

I'm pretty sure that will do it as for the primary, use the bottom lead for the B+ and top lead for the plate. It will work with the tap going to the plate but it may work a bit better using the top.
GL
Terry

When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!

Terry
#9

Hats off to Terry again for helping me diagnose the distortion issue and a special thanks to Codefox for giving us the tip on where to look. Seems the aftermarket transformer is not an exact match and is causing the problem. We did a quick fix with a couple of resisitors until I can find an original transformer.

Thanks again to all!!!

bm




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