Valiant Progress, of sorts...

[W7SOE]

I let enough time pass that I could look into the valiant again.  This Valiant is new to me and I have removed some modifications.

It still has a shorting issue at SW1 in the VFO box.  If I select crystals, instead of the VFO, before changing bands then the short doesn't happen.  I would like to try another SW1, if anyone has one I am in the market.

Since I had the VFO working on 40m anyway I thought I would go ahead to try to load up a dummy load.  It loaded up fine!  Small steps right?

I switched to AM mode and one of the series resistors (22 ohms?) in one of the modulator tube plate leads went up in smoke.  It's a Valiant, there will be smoke.  ;-)

Questions:
Looking at SW1 in the schematic there is 160m, 40m, and 11m indicated at the switch.  In what position is the switch depicted?  40m?  Then one click clockwise for 11m and counter-clockwise for 160m?

My bandswitch (SW3) is missing it's stop.  I can rotate the bandswitch all the way around.  If anyone has theirs open I would appreciate knowing where that stop should be.

What are the three frequency ranges output by the VFO?

Thanks All

Rich

[N8ETQ]

 
1.75 - 2.0,  7.0  - 7.42,  6.725 - 6.84.

http://bama.edebris.com/manuals/johnson/valiant/

GL

/Dan

[W7SOE]

 
1.75 - 2.0,  7.0  - 7.42,  6.725 - 6.84.

http://bama.edebris.com/manuals/johnson/valiant/

GL

/Dan

Thanks Dan, the manual I have didn't list them.

Rich

[W7SOE]

Thanks Dan, the manual I have didn't list them.

Rich

Correction, yes it does.  

And I now see the notation on the schematic that "all switches are in the extreme counterclockwise position"
Rich

[N1BCG]

I empathize with you about the Valiant/smoke correlation. One of my modulator plate resistors toasted with great fanfare because of the failure of a bias supply filter cap. That caused the modulators to draw big current due to the reduced bias.

Clark

[W6ZKH]

Now I understand why my 22 ohm plate resistors were missing on the Mod tubes... Well, I replaced them, and once I get the new loading cap installed and will see what the "smoke test" results will be... this rig has had many 'black spots' underneath the chassis and see where afew mods have been done.  I did replaced the resistor in the VFO to underneath, as I couldnt get it to fit inside the VFO box.  Time will tell I guess...

John W6ZKH

[W7SOE]

Checking for modulator bias before powering up in AM mode would have been a good thing, there was none!  That explains the smoke.

I replaced the resistor and set the bias to -40V.  This resulted in a pegged meter, measuring modulator current.  I adjusted the bias for ~80mA of resting current.  Not sure what the bias voltage is now, will have to check.

I adjusted the clamper and final neutralization.

The VFO is outputting the three frequency ranges as it should though the frequency is off and the oscillator drops out at the high end.  Hopefully the VFO just needs to be aligned.
But the transmitter now loads up fine (on 40m and 80m anyway) and the modulator seems to be working!  Progress.

I never did solve the SW1 shorting issue.  The #7 terminal causes a short between the two passing contacts when going from 40m to 80m.  One of those passing contacts has ground potential and the other 300V.  I am working around this now by switching off the VFO before changing bands.  Sigh.


Rich

[N1BCG]

My mod bias is set to achieve 60mA of resting current. Depending on where your info comes from, your bias setting should result in between 55 and 70mA. 80mA seems high...

[W7SOE]

My mod bias is set to achieve 60mA of resting current. Depending on where your info comes from, your bias setting should result in between 55 and 70mA. 80mA seems high...

I think I misread the manual.  It says the current should not go over 80mA while setting the bias voltage to -55V.  Will re-adjust tonight.

Rich

[N8ETQ]

Hey Rich,

      Glad you have the Valiant at least "Wheezing".   I've seen on
more than one occasion those 22 ohm "R"'s in the plate leads of
modulators, but there not on the schematics. (At least the several
I have seen). Wonder if that was a Hammy Hambone thing?

   There are/were some Valiant Bulletins that came out over
the production of the rig. I attached them here.

GL

/Dan

Now I understand why my 22 ohm plate resistors were missing on the Mod tubes... Well, I replaced them, and once I get the new loading cap installed and will see what the "smoke test" results will be... this rig has had many 'black spots' underneath the chassis and see where afew mods have been done.  I did replaced the resistor in the VFO to underneath, as I couldnt get it to fit inside the VFO box.  Time will tell I guess...

John W6ZKH

[W7SOE]

Dan,
   Thanks for that bulletin, I will compare those mods to my rig.

I have the original manual/schematic and it shows the 22 ohm resistors.

73

Rich

[W6ZKH]

Yes, my manual also shows the 22 ohm resistors, but they were missing when I got this monster.  Not only that, it looks like on of the "burn" marks was where the plate leads mounted on the terminal strip underneath, which was broken lug and black marks on chassis.  They installed 2 ceramic feedthru insulators and then used Nichrome wire from the insulator to the plates...duh... I think that bulletin is quite old, as my manual and original wiring shows R61 and R62 with the pots.  Speaking of that.... I cannot get the idle modulator current below 80 ma, and it is at full CCW on the pot.  Might had to take some resistance changes to get it down... now that I think about it, that is only on 40 meters as on 10 meters I can get it down to 50ma... hmmm, that I might have to think about...

John W6ZKH

[W7SOE]

The latest.
I adjusted the VFO trimmers, using a frequency counter at pin 9 of V3.

I can't get the 160 Lo to dial in, it won't set the frequency high enough.  I noticed that C14 (1000pF) and C16 (91pF) had been replaced with micas.  C16 was replaced with a lower value 82pF mica.
I would like to replace the 82PF cap with a proper 91pF cap.  There is also a 140 pf PTO cap in that region but I cannot find 140 pF micas anywhere.

Rich

[N1BCG]

Hi Rich,

Your frequency counter may be loading down the oscillator. Try using a pickup loop near the plate tank coil of V4 located just behind the oscillator chassis. It carries high voltage so your loop should be well insulated, but  that's a great place to measure the frequency since it will represent the actual operating frequency after multiplying (if applicable). Setting the Oscillator to TUNE or Mode to CW (without keying) should provide enough drive for a reading.

If that doesn't change the results then it could be that there's too much capacitance somewhere, indicated by the inability to tune to 2 mHz. Can you reach the top of 160 if both 160 trimmers are adjusted? Perhaps the "Low 160" trimmer is dragging everything down.

Clark

[W7SOE]

Thank you Chuck, I bet you are right! Especially since I have that signal Tee'd into the scope as well.  I will try your method tonight if I can.

Thank you again to you and all of the rest of you here.  What a great fount of knowledge and advice.

Rich

[WB5IRI]

If you have a stable, modern receiver with a digital readout, just tune it to 2mHz SSB, then set the Valiant VFO dial to the same freq, use the spot or tune position and tune the 160 HI slug to zero beat. Switch the receiver back and forth between upper and lower sideband to verify you are zeroed. There should be no difference in the sound when switching sidebands. Then repeat everything for the 160 low setting. Then go back and recheck the HI and then the low again, as there is some interaction. Do the same for the 40m and you're done. No messing with loops in the oscillator or fear of coming into contact with high voltage. The Valiant VFO marks are so close together 10 Hz accuracy is plenty more than good enough.

Finally, once you are done and before you physically move the Valiant in any way, apply a splotch of nail polish or something like it to the top of the slugs, as they tend to be sensitive to the slightest movement. The nail polish, once it dries, will hold them in place yet still break free easily if you ever need to recalibrate. You don't want to run the stuff down in the coil form, just across the top enough to keep the slug from moving. DO NOT use Thread Lock. Had a friend who used that once on a receiver and then was never able to turn the slugs afterward without destroying them. Nail Polish is weak and will do the job.

Love my Valiant!

Doug

[W7SOE]

Found the VFO alignment problem.  After replacing several caps with new micas I found (with a mirror) that C17, a tubular NPO cap, was replaced with a small ceramic disc cap.  The tubular cap was still there so I soldered in back in place and now the 80m/160m ranges aligns at both the high and low endpoints.

Onward!

Rich

[N2DTS]

You find resistors of low value in the plate/screen/grid circuits to kill parasitics and/or limit current in many designs.
In your case, they acted like fuses and give warning (by smell) otherwise you would have a cooked mod transformer and melted modulator plates.

I had a 50 ohm 2 watt resistor in the 6146 cathode of my exciter that cooked up nicely when it was keyed for a while with no load by mistake.

I was glad it was there.

For your modulator resting current, the bias is low or the screen or plate voltage is high, or the shunt is way off.

[W7SOE]

I had my first successful QSO on the Valiant with K7PP. Pete gave it a good audio report.

I have noticed another anomaly though. When, in AM mode, I throw the HV switch I get a normal carrier but no modulation. If I use the PTT switch then all is normal. This is very odd as, according to the schematic, the PTT switch and the HV switch do the same thing. They merely ground one side of the relay coil.

Something strange is afoot. Maybe fixing this will remedy my SW1 shorting issue.

Hope springs eternal with the Valiant.

Rich

[N1BCG]

Congratulations on the QSO! You are correct about the function of that switch "according to the schematic". I found numerous schematic deviations when restoring my Valiant, so you may be experiencing the same.

More likely is that your microphone is *not* set or wired for VOX. When it is, the microphone audio is always available on the audio pin (#1) of the connector. In this case, it's possible that audio is only available when your microphone PTT switch is used. The PTT switch in my D-104 is wired to short the audio pin to ground whenever it's not clenched to transmit.

Using the HV switch to transmit would leave the microphone audio shorted in this case. If this turns out to be the case, you could always unsolder the switch that shorts the microphone (VOX mode) so you can use either switch for transmitting.

Clark

[W7SOE]

I am a moron.  I am using an amplified D-104.  Of course there is no audio until I key the mike.

If I had a dollar for every time I did this sort of thing...........

Rich

[N1BCG]

You're in good company as we've all had those moments. What differentiates us is whether we're willing to admit it or not.

In this particular case, that of getting a rig working, it's easy to overlook the obvious in favor of a "Now What's Wrong?" assumption of something more involved.

I experienced that after replacing blown loading caps and then forgetting to replace my Valiant's 9 pin accessory plug on the back. Valiants don't do much with that plug removed!

[WD8BIL]

Yup....... first transmitter I ever built had no indicator lamps at all. Tried to call CQ one day and no power outpoot. Took me 10 minutes to realize I hadn't turned the darn thing ON!!

[KA2DZT]

Yup....... first transmitter I ever built had no indicator lamps at all. Tried to call CQ one day and no power outpoot. Took me 10 minutes to realize I hadn't turned the darn thing ON!!

Budley

With practice you'll get the hang of things,  don't give up.

Fred

[W7SOE]

The Valiant is in it's case!  For how long though?  ;-)

Thanks for all the help guys.

Rich