Valiant Making Progress

[ka4koe]

Checked modulation on a scope. I am hearing my modulation and seeing it on the bandscope, but the oscilloscope/wattmeter are a different story. Modulation peaks on an analog meter go up to about 150 watts with carrier at 100 watts, final loaded to around 300 mils with grid at 7.5 mA, resting mod current at 70 mA. Does this seem right?

[KA2DZT]

That does seem OK for the loading and grid current, resting mod current is also about right.

The meter you're using may not respond fast enough to see peak power.  You need a peak reading meter.

[ka4koe]

Well, I will tell you this Flex has spoiled me. It has a speech compandor, adjustable bandwidth audio, etc. With the amplifier in line giving 100 watts carrier, it swings really well on the meter, while staying in the correct ALC zone. I've set it up using W1AEX's online procedure; the audio simply rocks and usually garners unsolicited compliments (not pertaining to on-air content; that's another story, HI).

I have read the Valiant's modulator (iron and 6146's) is not up to the task at hand. I did see some improvement when I swapped out the 12AX7 in the first audio stage.

If this is as good as a bone stock Valiant will do, then I'll stop for now and work on the VFO and the female microphone chassis jack (worn out), and a few other things. When I get the classic set up where I want it with the R388, then I'll consider doing the audio mods.

Frankly, I've been working on this transmitter for over two months and I want to play with it a bit and solicit harsh, cruel comments with regards to my on-air audio...."Gee Philip, you sounded so much better with the Flex......). 

However, when asked why would I work on a transmitter when I already own a first class exciter, the answer is simple. How does one learn hands on electronics by clicking a mouse on a computer display?

I have learned more practical electronics by building my theremin, restoring the R388, and fighting with this Valiant.....and I have a degree in this stuff.

The sad truth of the matter is many of our top line engineering schools are turning out kids who don't know which end of a soldering iron to grasp.

[ka4koe]

Radio is definitely modulating. the sweet spot seems to be around 290 mils plate, 7.5 mA grid. Better swing on the scope than before. The only thing left is maybe install a different fuse holder in the radio (drill round hole in back type). I have a flat screw on type inside currently....in retrospect, if the fuse blows you likely have a problem anyway and will have to disassemble it.

Also, the VFO needs work of course. Chernobyl replaced. The circuit board around the tubes looks fine, so I don't think it had gone into runaway yet. Just not sure if I am going to go the trouble at the moment. I'm tired of working on it.

I will rewire the bypassed clipper and see how it does. Just so I can make an educated decision myself after seeing how much worse it will make my PW signal sound.

Philip

[ka4koe]

File of work to date...

[ka4koe]

Now the chassis connector for the two pin microphone plug is intermittent. A brand spanking new Amphenol 80-PCF2 is on the way. I'm sure this connector has played a part in my journey through the hollow state wonderland.

In other news, the Dow Key is wired up and ready to go. The sucker makes a very satisfying CLICK when energized.

If I'm lucky, I'll be on the air prior to the long weekend....I hope you fine folks aren't tired of my multiple postings. I DO appreciate all the kind advice and encouragement.

FEELEEP

[KC2TAU]

Don't be afraid to step back and rest a bit as well. If you work past the point of exhaustion/interest you might find yourself less able to pay attention to details and to do the best job possible. A fresh mind results in better work.

[ka4koe]

Got the clipper rewired and its working. Found a couple of pins on the third audio that may have been touching. Traced audio clean through the entire chain. Looked at RF output on a scope. It appears to be modulating 100% modulation or better.

Audio sounds sweet and clean....not bad at all. Aside from the bad mic jack, the transmitter is ready for prime time.

"THREE CHEERS AND A TIGER FOR ME, I HAVE WON!!!!"

The genie with the light brown hare, in WB Cartoon " A Lad and His Lamp".

Link here

https://www.youtube.com/watch?v=LvGsfXXXCMo

Philip

[WA2OLZ]

Well done, Mr. One-L! It has been educational as well as entertaining following your exploits.

BTW - What mic are you using on the Valiant?

Jack
WA2OLZ

[ka4koe]

Still need to make up jumpers for coax and install that. Have both an EV638 and D104. We'll use what sounds best.

[ka4koe]

Drifting VFO problem appears to be solved by replacement of 0A2. However, the waveform looks junky on 40m. May replace the oscillator tube if I can find one here in the shack.

[ka4koe]

Is there an easy way to get the VFO cover back on so that all the little adjusters line up?

[ka4koe]

Easy. Remove the adjusters. Keep the hardware. Use a long handled insulated tuning tool to adjust the VFO.
Rig back on the air with new VFO tubes and a microphonium jackum. Works good now, although I wonder if the final tubes are a little soft, as I have trouble getting up to 7.5 mA grid whilst in the AM mode.

I think we can likely close this chapter out and move on to the next challenge. I need to modify the R388 to switch to a mute with a simple relay closure (there is no voltage internally with the radio, you have to provide 12VDC in series with the mute switch). Then align the receiver, and we can move on to the HQ180 after that.

PHILIP

[ka4koe]

Determined that the Valiant doesn't work good on AM is the switch is in SSB, no matter what band one is on.

Philip

[WD5JKO]

Phillip,

  Get that Valiant on 14330 tonight, about 7 pm EST. Both Ralph KD6OS/5 and myself plan to be on.

Jim
WD5JKO

[ka4koe]

Will have to be another evening. Been ill all day.

[ka4koe]

Can anyone tell me a good place to find doorknob caps for the loading padders?

[WD5JKO]

Will have to be another evening. Been ill all day.

  Phil,

   I hear you as I write on 14,325 as about an S7, and Q5...

The audio is a bit muffled, but quite copyable.

Jim
WD5JKO

[ka4koe]

Muffled mic was EV638. Swapped over to D104. Anyone has a Valiant here is a tuning aid. I use a manual tuna and logging settings helps out the finals.

Philip