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Author Topic: Johnson Viking Ranger Mods  (Read 5337 times)
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n8fvj
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« Reply #25 on: August 15, 2023, 03:36:20 PM »

I also found this on AMfone posted in 2015. Your comments please DMOD.

If you're going to re-post a post from somewhere back in time, it's important to the readers to identify the writer(poster - and it's good common courtesy) and to provide a link to the entire thread. Readers can then judge the validity of the past and current posts relative to the topic.

Updated Pete.
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DMOD
AC0OB - A Place where Thermionic Emitters Rule!
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« Reply #26 on: August 15, 2023, 05:31:35 PM »

I also found this on AMfone posted in 2015 by member Tim WA1HnyLR.

Your comments please DMOD.


I agree with most everything except for the first 12AX7A (V7A) stage. See my modifications in the dotted line, upper left, Schematic 1. My experimentation shows a 3.3 megaohm resistor on Pin 2 of V7A is of sufficient loading to get the low's needed. What he didn't take into consideration is that by going to a 10 megaohm grid resistor, you increase grid leak bias, so he should have changed R18 from 4.7k to some lower value to get the proper grid bias.

Tim's main contribution here (and a good one) was to move the T2 tertiary winding's feedback to a low impedance path, the cathode of V7B, Pin 8. His modification is shown in the lower right in broken line format, Schematic 1.

Tim wrote-up a number of mods for the Ranger, with one using a phase splitter and removing the T3 interstage transformer, but that is beside the point here.

The 1614 screen Voltage regulator is shown on Page 2, which meets the RCA specs for ClassAB1 modulators.

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DMOD
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« Reply #27 on: August 15, 2023, 05:52:32 PM »

quite a cuss and discussion  Grin

Timtron wrote up a lot about EFJ Ranger mods as well as the other folks mentioned here.  each writer stated importance.

I will mention 6146 and variants.  the Ranger does not have an adjustable neutrilsation circuit but rather seems to use a novel plate capacitor grounding method (my opinion).  works ok with plain 6146 maybe not so good with "improvements" made by RCA back then and suffixes added.  Collins went down a similar path with the S line about the same time

And in the Ranger's I and II, both the 6146 grid AND the plate have parasitic suppressors.

I have not had any parasitic problems with any of the 6146 variants in the Rangers.
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Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
n8fvj
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« Reply #28 on: August 15, 2023, 07:02:40 PM »

Thanks DMOD
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n8fvj
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« Reply #29 on: August 16, 2023, 04:31:07 AM »

BTW- I am changing the T2 modulation transformer feedback (tertiary) winding to Tims suggestion at 12AX7 (V7B) tube that is originally connected at the 12AU7.
The 1614 tubes now Sovtek 6L6WXT+ will have zener regulation at the tube screens.
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