Valiant

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Originally Posted by w2amr

This transmitter came from the estate of my friend Phil/KB2MAM. Getting some of these Johnson transmitters in and out of the Cabinet is a real pain in the ass. He solved this by putting the Valiant in a Johnson invader Cabinet , which had a hinged door on the top. Then he cut the bottom of the cabinet out, and added a hinge. Just remove 5 screws and it swings open. Very slick.
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Clever idea of Phil to use the hinged cabinet. Otherwise the only way to work on those Valiants is to pull the chassis out of the cabinet. That is one thing I liked about the Viking 2. You can open the top and bottom easily. I noticed that the two big mercury HV rectifiers are missing. Are there solid state rectifiers mounted underneath the chassis ? I remember the old 866's were a major PITA, often arcing over internally if they weren't given ample time to warm up. I remember solving that problem in my Valiant by putting a pair of argon HV rectifiers in place of the 866's. Much less problematic. Then I switched to a pair of those Peter Dahl solid state plug-in replacements. I kind of miss playing around with the old radios. Maybe the radio bug will bite me again soon and I'll get back into it. My main problem is I have too many hobbies and interests that I really love. But one day the radio bug will sting me back into the radio hobby. It always does. :)

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Originally Posted by n2ize

Clever idea of Phil to use the hinged cabinet. Otherwise the only way to work on those Valiants is to pull the chassis out of the cabinet. That is one thing I liked about the Viking 2. You can open the top and bottom easily. I noticed that the two big mercury HV rectifiers are missing. Are there solid state rectifiers mounted underneath the chassis ? I remember the old 866's were a major PITA, often arcing over internally if they weren't given ample time to warm up. I remember solving that problem in my Valiant by putting a pair of argon HV rectifiers in place of the 866's. Much less problematic. Then I switched to a pair of those Peter Dahl solid state plug-in replacements. I kind of miss playing around with the old radios. Maybe the radio bug will bite me again soon and I'll get back into it. My main problem is I have too many hobbies and interests that I really love. But one day the radio bug will sting me back into the radio hobby. It always does. :)

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The mercury vapor rectifiers have been replaced with K2AW diode stacks , epoxied to the underside of the chassis.

There are a few simple mods to get rid of the telephone audio and give it that AM Gangsta sound. That D-104 needs a higher load impedance, change the first audio grid resistor to 10M. Then disconnect and bypass the clipper/filter and change the coupling caps to .05uF 600V Mylar keeping the black marked outside foil where it is on the original paper caps. It's that way to shield against hum pickup, always on the high side of the circuit. Those things have a bad habit of developing leakage and the first ting you do with any boat anchor is entirely recap it. That's the easy part, but you don't need to go all the way unless you want to. 6146s don't make very good modulators, a socket change and a pair of 807s work better. Hint: if you can get 6BG6s, the octal version of the 807, all you need to do is change the pin connections.

One last thing, it was designed to operate with 110VAC mains voltage, with today's 115-120VAC and with solid state rectifiers LV and HV are considerably higher. You might want to check out the filter caps, the old original electrolytics should have been changed out already, so check the operating voltage against measured in CW key up and make sure there is at least 20% headroom. If not I'm reasonably sure you know how to connect 450VDC electrolytics in series with a 470K 1/2W resistor in parallel with a .01uF 600V ceramic cap across each one.

Yeah, I love boat anchors and I'm a hollow state (tubes) analog man in a solid state digital world. They say real radios glow in the dark. I say 12V is for wimps, real radios can kill you.

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Originally Posted by kb2vxa

There are a few simple mods to get rid of the telephone audio and give it that AM Gangsta sound. That D-104 needs a higher load impedance, change the first audio grid resistor to 10M. Then disconnect and bypass the clipper/filter and change the coupling caps to .05uF 600V Mylar keeping the black marked outside foil where it is on the original paper caps. It's that way to shield against hum pickup, always on the high side of the circuit. Those things have a bad habit of developing leakage and the first ting you do with any boat anchor is entirely recap it. That's the easy part, but you don't need to go all the way unless you want to. 6146s don't make very good modulators, a socket change and a pair of 807s work better. Hint: if you can get 6BG6s, the octal version of the 807, all you need to do is change the pin connections.

One last thing, it was designed to operate with 110VAC mains voltage, with today's 115-120VAC and with solid state rectifiers LV and HV are considerably higher. You might want to check out the filter caps, the old original electrolytics should have been changed out already, so check the operating voltage against measured in CW key up and make sure there is at least 20% headroom. If not I'm reasonably sure you know how to connect 450VDC electrolytics in series with a 470K 1/2W resistor in parallel with a .01uF 600V ceramic cap across each one.

Yeah, I love boat anchors and I'm a hollow state (tubes) analog man in a solid state digital world. They say real radios glow in the dark. I say 12V is for wimps, real radios can kill you.

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All the audio mods were done when I got it, And I get very good reports on how it sounds. Phil went over every inch of this transmitter and it's rock solid. All I have to do is clean the pots & switch contacts from time to time.

Ah, then Phil certainly knows what he's doing and saved you the work. You didn't mention the modulators. 6146s are RF tubes and Johnson had the right idea using 807s in the Viking 1 and 2, why they used 6146s in the Valiant is a bit of a mystery.

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Originally Posted by kb2vxa

Ah, then Phil certainly knows what he's doing and saved you the work. You didn't mention the modulators. 6146s are RF tubes and Johnson had the right idea using 807s in the Viking 1 and 2, why they used 6146s in the Valiant is a bit of a mystery.

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They also used 807's in the Viking Mobile transmitter.