The AM Forum

Howdy!
I've had this Valiant about 19 years and have not used it much.
It is a very nice factory assembled unit...I think it is anyway...has riveted tube sockets.

Before turning it on I replaced the bias, LV and HV lytics with new...not NOS parts.
Replaced the 866A's with 3B28.
Tested all tubes and in general spiffied it up a bit for the next round.
I replaced the Chernobyl resistor.
Other than that, it is un-modified...so far.

Here's the problem....
If I remember correctly...I never used it other than 80mtrs...and not much of that.
Cut to last week.....
It works on 160 and 80 and I made a few contacts and sounds ok.

There is no grid drive on 40 through 11mtrs.

I removed the 160 VFO trimmer phenolic trimmer adjuster and inserted a RF sniffer probe into the VFO box and I get 1.8xx reading on the counter when the b/s knob is on 160/80.

I change the b/s to 40mtrs and the VFO sniffs 7.xx (same freq as VFO pointer)
To me, this means the VFO is generating the correct frequencies.
So far....so good.

The 7.xx signal should go straight through the 6CL6 and 5763...there is no need to double or triple on 40mtrs....but it dosen't....no drive.

The meter works fine with the expected current readings....and I measured the shunts too....they are reasonably close.

Same thing on the rest of the band positions....the VFO is on 7.xx and the b/s can be on any other band and there is no multiplication...and no drive of cuss.

I DID find that the L6A coil tap for 20mtrs was missing....never installed.
And....the 15mtr tap was installed but on the wrong (clip 4) SW3A (rear) clip.
I moved the 15mtr tap to the correct location (clip 5) and installed the missing tap (clip 4) and fired it up. (per assy manual page 7 steps H4, 5, 6.)
Of cuss....it still don't woik!

Next....even though the VFO seems to be working correctly I plugged in a 7.150 xtal just to eliminate the VFO  and it's b/s.
Same thing....no drive 40 through 11mtrs.

I replaced the 6CL6 and 5763 and no change.

I replaced C29 50pf coupling off 6CL6.6....nada.

I grid dipped L6A & L6B and I see a decent dip for 160 and 80mtrs that responds when I turn C7.
C7 is close to the expected position per the manual.

The rest of the bands show no dip or very little dip.

Right now....I'm dipped....skunked...done.

Somebody rescue me!!

Dirty contacts on the band switch????

Yes..  Take a tooth brush and Deoxit and SCRUB the band switches.  ALL of them. Turn them to a no contact position and slightly bend them down.  It takes 5 minutes and might solve your issue. Mine was missing two bands. This fixed it.

Good luck!

c

Nope....dirty band switches was the first thing I thought of....I forgot to add that to the original rant.

On sw3A (rear) contact 4 & 5 there is an 11T coil that is not shown on the schematic.
I removed it and there was no change...still didnt work on 40>11mtrs.
If anyone can take a picture of the front and back of SW3A I would appreciate it....or look and see if that coil is there.
There is a second 11T coil (L16) on contact 11 & 12 and is shown on the schiz.

Love your avatar, Dave  ;D

A little Deoxit goes a long way.  Don't douche it down; rather, apply a bit of deoxit to a Q-tip and use that to apply it to the switch rotors.  You don't want to saturate the insulation on the switch wafers, be they bakelite or ceramic.

You must scrub the Johnson switches and wafers.  Pretty damn hard with a brush. If you dont, You will have them arc. Carbon builds up at the rivets. You will see the carbon tracks if you look close. Enough scrubbing and enough deoxit will get them spotless and white again.

Mine has the two Coils...

C

Ok guys....thanks for all that.
I didnt check the clips for tension so that's next.
Thanks for the bit about the 2 coils.....
I'll post the outcome.

I re-cleaned the band switches and mode switches, scrubbed the hell out of them until the Deoxit started to foam. I looked at every, single contact and rotated the wafer through...each of them has good contact follow...meaning that the clip expands nicely as the tang rotates through......it still won't work on any band but 160 and 80mtrs.
If anyone else has any suggestions.....I'm listening.

Damn.. Sorry. Now at least you have good band switches.. 

Acc plug in back have good tight connections?

Clamper tube adjustment set correctly?

Screen resistor ok on final?  Sometimes they go. 

Check the plate choke and the caps at the bottom. Mine burned one up once.

Make sure the Doorknob is ok  Someone put a low voltage one in on one valiant and it was dead.  I use 5k or 10kv 1000puf.


C

Howdy,

Check yer Grounds OM, Solder Joints all connection points with a Magnifier Glass sounds Crazy but it Sounds like a connection issue to me...somewhere in there, If all Active Devices are operating no Sig getting through.

73
Jack.

Thanks again for the suggestions guys.....

The entire rig operates normally on 160 & 80mtrs so I wouldnt think the acc plug, screens or anything else in the PA would have a problem....at least at this point.
The rig won't make any drive on 40>11mtrs.
The 5763 does not double or triple.

The clamper is set to 10ma.

The doorknob is the original 500pf 20kv unit on the 'early' units......and the rig has the bias pots mod as well.
I dont have any way to identify when it was built but this thing is so clean that I'm sure it was a closet classic for decades before I got it.
Little wonder that it wasn't used.....it probably wouldnt work for anyone else either!
There is no evidence of anyone else troubleshooting it either....it's never been hacked.

I located a local source of 2000pf 20kv doorknobs and I'll put one of em' on there....that is if I can get it fixed......summer is coming so I better hurry up before the fishing season is here.....I don't wanna foul up the lakes with oversized weights.

I re-soldered all connections on SW3A front and rear and a few others here and there.

I guess the damn thing is was a kit after all because the decal on the back does not have a -2 after the model number.
Congrats to whoever assembled it even though he is likely dead for years.....he did a great job but made a mistake or two....mebby more!

There is still some question in my mind if SW3A is assembled correctly....I'll post some pix soon.
I have a the .pdf assy manual but it dosen't have the drawings showing orientation etc of the componants.

Boy. I wish I could help you further.. Time to trace it down step by step with the manual

C

Time to break out the scope and see where you're losing the signal.

With the VFO connected, bandswitch on 80M, put a scope probe on pin 9 (grid input) of the 6CL6. Verify signal appears there. Now switch to 40 M and verify signal is at the grid. (Yes) then, put the scope probe on output side of C29 (6CL6 plate coupling cap). Verify signal is there. (Yes) move on to the 5763 stage and repeat the same process. You should also verify tube voltages of the 6CL6 and the 5763. First in the 80 or 160 position (ones that work), and then repeat checking tube voltages in a bandswitch position that doesn't work. Random part or tube replacements generally doesn't always solve a problem.

Ok....but first.....here's a couple of pix of SW3A front and rear.

Note that the index mark on the center of the wafer is 180 degrees from the other wafer on the same b/s shaft. The rear wafer switches the PA coil taps.
I've never seen a rig of any kind where this is so....

Anyone see anything wrong here??
Wiring...etc....


Urrrgg....I made a mistake labeling the pix....this is the FRONT view....not the rear.

Here's the REAR view of SW3A.
I labeled the pix incorrectly.

If you really need me too.. I will lug my working Valiant out of the storage room, Pull the case and take close ups.. A friend is comming over at some point today to help me lug some stuff around anyways.

C

Thanks Clark....that would be great....break out the chain hoist and let the rough side drag!!
If you could try to get the same view on your pix it would make for easier stare and compare considering that I dont have the pictorial of this area.
The b/s is in the 160mtr position.

Note that the black wire on lug 4 in the rear view (20mtr tap) is supposed to be red.
This is the missing tap I added.....I didnt have any red wire.

Does your valiant have the SIDE adjustment Bias pots? I have three valients here.. One old factory made one with the NO side mounted pots.  One that has the side mounted pots and one new in the box valiant that has the side pots.

i want to take pictures of the one that matches yours.  Give me the serial, I will take pics of the one that is close.

C

Well....it seems like this unit was a kit after all because the model number does not have the -2 of the factory assd units.
It has the side mounted bias adjust pots but are obviously added as a mod later...plus it has the 500pf doorknob of the earlier units.
The s/n is...as near as I can tell on the ancient decal is 20794.

Alright.. I will see what I can do.. I have to wait until my friend gets here..  to help me lug the thing to the table top. I will yank the case and take the photos for you.  I know how frusterating it is to deal with these things.  I am going to make T shirts that say "it takes a valiant effort, to keep a johnson running" ...



C

Mine has the side bias pots obviously added later.  Someone (not me) labeled 'em in magic marker "Bi-ASS"  ;D

Did you check the voltages? Use a scope to check the signal at the grid of the 6CL6 and 5763?

Clark.....that would make a cool T-shirt for sure.....or mebby a pix on the shirt of a Valiant with Johnny's logo saying 'Set your biASS'....HEH

My avitar is me wondering what to do next while working on a thrashed Collins KWM-2A that I rescued.
It turned out to be a very nice operating unit and is in service today in Cincinatti.
So much for self portraits.

The voltages and resistances are ok....I havent scoped it yet....but, I have traced it and I don't see any errors other than the 20mtr tap that I fixed.
If Clark's rig compares to this one then I'll start scoping with a counter attached to determine the freq of the signal.
The 5763 works ok as long as it dosen't have to multiply....it might have a mis-marked part or dead part....who knows.
That is the reason for the emphasis on the driver b/s assy..

Ok.. My friend is still not here... LOL. 

I wanted to make the T shirts for a while.. I am going to have them in HAM sizes.  2XL tall and 3X.. :)  I want to use the old Ef johnson logo with a pic of an old Valiant on the back. Great for Swap and swindles..

Nobody in there right mind would choose a valiant over other transmitters.  They constantly crap out and have troubles. But something keeps me from getting rid of them :)





C

Dave,
Like Pete said, with a scope I think you will zero right in on the problem.  There is a lot working on the rig so that leave little to check to gain operation on the higher bands.  If a doubler is not doubling, check the "L" and the "C" to make sure those values are still on.  With a scope use the formula F=1/T to determine what frequency your looking at.  I have seen people look at a scope and they think they are looking at the doubler frequency but they are looking at the fundamental!  Counters are good at measuring exact frequencies, but you can't beat a scope for trouble shooting a BA.  Its nice to see the amplitude and well as the waveform quality.   

I know a lot of guys using Valiant's and they have been on the air for years without any problems. 
 
Joe, W3GMS

For dang sure.....I've got a nice DX100 and 5100B I'm gonna do next and a ratted out terrible condition Ranger.
Funny thing....they all work....uhh...at least 20 years ago they did!
More projects....

Thanks Joe....that's exactly how I intend to do it.

This thought is general and not Valiant specific, but . . .

A friend bought a Valiant, and found inadequate output.

The problem was traced to improper bypass capacitors, but with a cute twist.

The parts list showed the use of CERAMIC capacitors for bypassing the plate RF choke.  The original owner had replaced the bypasses with tubular paper-dielectric capacitors which were enclosed in a, yes, ceramic, tube!

The original owner apparently didn't understand that the parts-list specification of ceramic capacitors was directed at the dielectric material and not the housing material!  The caps he had installed had a self-resonant frequency around 2 mHz, and of course got lousier (more inductive) as frequency increased.

Replacing the ceramic-housed paper caps with ceramic-dielectric disk caps, brought back full output to the Valiant.

I've seen many an error, and have myself made even more, but something about that one tickled me a bit!

73 de al h
w8vr

Thanks Al.....that's interesting. This rig has the original parts and I have substituted a few then replaced the originals if no improvement.
So far, it still dosen't work and am hoping for some help in the SW3 bandswitch area.

I scoped it and that just confirmed what I already knew....7.xxx from the VFO will not get through the 5763 and if course it won't multiply for the 20>10mtr bands.
I think there is something wrong with the b/s wiring but I havent found it yet.
Still no drive on 40>11mtrs.
160 and 80mtrs work ok but the driver log scale on the knob is at the wrong position for max grid drive as shown in the manual...yes, the knob is installed correctly.

Hopefully...I can find the problem before I get really pissed off and shove it over the side!

I'm still thrashing this thing.
I printed the construction manual and went through it checking the wiring.
I can't find any errors.

The tx has good output on 160 and 80mtrs.

No drive on the exciter at all on 40>11mtrs.....not that I care if it works on 11mtrs but that's the story.

I've done the resistance and voltage checks and scope/w counter observations and I still can't find it....cleaned the b/s and all other switches....removed the turret cap, disconnected the neutralizing cap....bla, bla....

I still believe there is something wrong in the exciter band switch/tuned ckts that prevents V4 from doubling and tripleing on 20>11mtrs. It isn't open...its non-resonant.

The VFO puts out 1.8xx and V4 doubles to 3.6xx and the tx works fine on 80mtrs.
BUT.....the exciter tune cap is wayyyy off the expected log position at the specified position.
Meaning that using the Table 4 'Typical Dial Settings' chart at 3.55 the exciter tune should peak the drive at about 38 on the dial. It peaks at 'zero' on the dial.....not good.

The 160mtr exciter dial position is very close to the expected position.

Change the b/s to 40mtrs and the VFO puts out 7.xxx like it should and should go straight through V4 without doubling...but it dosen't.

When the b/s is changed to any other higher band 20>11mtrs V4 does not double, triple etc. the 7.xxx VFO signal.
I get the same result using a 7125 and 7150mhz xtal....which totally eliminates the VFO.

Does anyone have any more ideas.....????

Dave,

Any chance connections to L6A have been reversed or it was installed backwards?  Do you know if this rig ever worked on 40 and up?  Was it kit built?

A grid dip meter would be handy but in lieu of that visually inspect.  For 160, all of L6A and L6B should be in circuit; most of the inductance will be switched in for 80 with correspondingly smaller amounts for the higher bands.  Reversed coil or tap wiring is consistent with working fine on 160 but problematic on other ranges.

Dave:

Here's a thought:

If you're a man of great trust, send the Valiant to me, and I'll try to repair it for you.  No charge, just for the challenge and the fun.  You pay shipping and insurance both ways.

I've a reasonably well-equipped lab, am a retired E.E., and have 60+ years experience as a technically-oriented ham.  See my website at www.w8vr.org for examples of workmanship.

I would do my best to fix it for you on your agreement that (a) I may fail and end up returning the thing to you unrepaired, and (b) My efforts may result in the need for parts, where you would pay for any parts needed, and you will be responsible for finding any special Valiant parts (eg., bandswitches, transformers, etc.), and (c) At worst, there's a long-shot chance that I might somehow destroy the thing, but for which I would not be liable.

If you're interested, let me know.

al hart, w8vr
farmington hills, mi

Dave, where exactly are you losing the signal on the scope?

Scope the grid of V4 as you sweep the band switch up the bands.  If you're getting healthy signal there, and getting little or nothing on the plate of V4, I'd suspect that that multi-section/multi-tap coil in the plate circuit of V4 is wired incorrectly, or the switch wafer is 180 degrees out of phase.  Make sure that V4 is getting its proper screen and plate voltages in all bands.

See if C7 is at the far closed or far open end of its travel on 80.  If far closed, it's probably using the section of the coil meant for 40.  Sometimes the knobs get pulled and replaced in a haphazard manner so I wouldn't put a lot of stock in the knob calibration until you confirm 0 is actually full mesh closed.

I'll try to answer all questions.....
Rodger....L6A cannot be installed backwards due to it's original configuration.
The ceramic form has mounting holes on one end only.
It is not wired backwards either....although while checking this last week I DID discover that the 15mtr tap was on the 20mtr b/s contact and the 20mtr tap was never installed.
I corrected that and of course there was no change...nor did I expect a change.

Band switch SW3A rear is in contact only with contact 1 on the 160 band and as the b/s is rotated to higher bands, the b/s shorts out each L6A coil segment in turn starting from the top of L6A.
All b/s taps have continouity from L6A to their correct b/s contacts when the b/s is in the 160 mtr position. L6A is good end to end also.
The b/s is oriented correctly according to the pictorial....although the shaft index mark is 180 degrees from SW3B which is also installed correctly according to the pictorial.

Last week I also grid dipped the exciter on each band.....160 and 80 dips but there is no dip on any other band. I tried looking for a dip...any dip....nothing.
This thing is dipping ME!!!

As I mentioned previously....I have been through the entire construction manual for the exciter section and it is all wired correctly. (includes the ckt changes in the operators manual for softer keying)

Visually, I have been over this thing 10 times at least taking my time....10 days at least.

Johnny.....I'm not losing the signal on the scope.
VFO freq is on V4.8 AND V4.1.....That is the problem!!!
The exciter/mult plate ckt is not resonant on 40>11mtrs so V4 dosen't multiply.
I did a resistance and voltage check again today just to make sure....not only are the voltages pretty close to the manual but they are the same from band to band except for the plate and screen voltages that are a bit different because the tube is not operating on the bad bands.

C7 is flush closed when the exciter knob logging scale is at zero...per the book....first thang I did.
160 is about 10 points high at resonance but 80 resonates at zero....these measurements were done according to table something or other I previously mentioned.

That's it for the answers.....I guess the only thing to do is wholesale out the mica caps with decent parts.....unless C7 has some problem like an unsoldered rotor or something dumb like that.....meanwhile....I'm open to any further ideas.

OK, if you're 100% sure the coils are in the right position on the bandswitches, and the coils have continuity thru the bandswitch, the other thing that will upset a resonant circuit is the capacitance.

Presuming the variable capacitor(s) haven't been replaced, I suspect perhaps one of the mica coupling caps has gone south and is either wrecking the Q of the circuit, or has changed value enough to affect the resonant frequency of the tank.   Also is C75 (the 10 pF from the bottom of L15 to the plate of V4) installed correctly?

If you have, or can borrow, a grid dip meter it'll be easy to check the resonant freq of the mult tank at each band position.  You can do this with a sig gen and a scope also (with the power OFF) and light coupling to the tank from the sig gen so you don't wreck the Q of the tank with the low impedance of the sig gen.

If you don't have a dip meter, set the Valiant to a blank crystal position and set it for the 40 meter band with the exciter tuning knob at 50.  Attach your signal generator through a DC blocking capacitor to the control grid of the multiplier tube and attach your scope with a 10X probe to the grid pin of one of the final tubes.

Set your signal generator to 7 mhz. and see if you can peak the scope display with the exciter tuning.  If not, set the exciter tuning knob back to 50 and sweep your signal generator while watching for a peak response on the scope to see where the plate circuit of the multiplier is actually tuned.

Here is a thought, or two:

in 160 and 80m position, SW3a has no effect.

in those positions, the plate for V3 buffer has then L5 + L15(choke) + L41 over to the keyer circuit

in examining the circuit, the bandswitch from 80 to 40 seems to have the effect of shorting across L15 ?!
this puts L41 in series with L5 (? my schematic is blurry on this part)

L41 (52uH) seems to be a fixed part, and  must show continuity for active 160/80 (needed to supply B+ to V3)

I am wondering, what with your earlier discussion of missing or misplaced taps, and of the dial indication being "way off", if now that you have the coil taps connected as desired, that the tuning of L5 is off ?

have you peaked it ?

normal technique is to peak starting from 10 meters and working on down.

I had some no-drive moments on my V-500, until I did the peaking correctly.

73
tom
w6tjk

Thanks to everyone for all your thoughtful suggestions....I have tried them all without success as well as some other things as well....and there is no improvement.

The damn thing DOES work on 80mtrs so perhaps I'll let you all sample the lousy audio..... ???
Actually, I think I'll start the same process with the DX-100 or the 5100B and see wha' happens. ::)

So now...reluctantly...after 3 weeks.....I'm done...stick a fork in me....dawgmeat.
It's heading for the back burner...waaaaayy back. :-[

Thanks Again ;)

Actually, you probably should have put it aside after the first week and then some back to it several weeks later with a fresh mindset. When I have a repair issue with a rig, I generally give myself 5 hours or less to find the problem(s). If I can't solve it within that time, I move on to something else. Weeks later I'll come back to it and generally something that I gloss over the first time will stand out as the culprit.

Like Pete said, put it aside for a bit and then come back to it.  Weird things happen to rigs and a fresh approach will often reveal  the true problem and solution.

I recently finished going through a Signal One CX-7A I picked up last fall.  After correcting some wiring errors and a couple of other faults I got the CX-7A running properly and made a few contacts.  Earlier I had picked up a nice looking Alpha 274 (twin 8874) amplifier and felt it would make a nice match for the Signal One.  With the Alpha in line the formerly nice audio from the transceiver was very distorted.  Since I had never used the Alpha before I assumed an amp problem and given the response of the plate current to the drive level from the CX-7A I assumed the problem was in the RF sense electronic bias switching section.  I found a couple of leaky electrolytic caps but replacement made no difference and when I defeated the interlocks and measured the bias system in operation it was performing perfectly dropping to intermediate bias when "keyed" and to operating level with a small amount of drive.  I then got smart and hooked the amp to a recently repaired Icom IC-751 and found the Alpha amp worked and sounded great with the Icom.  The real problem was the wrong size RF bypass cap installed on the Signal One microphone input allowing RF into the audio.

But then another problem!  While checking through the bias/control card for the Alpha amp I discovered several larger wattage carbon resistors out of spec so I replaced them with modern metal oxide resistors.  When I plugged the card back in the Alpha would no longer go into transmit.  I assumed I made an error so I rechecked all of my work and connections and found nothing wrong.  I put a shorting plug into the back of the Alpha to rule out a transceiver or cable problem.  After a bit more head scratching and measurement I found the problem was the RCA phono jack on the amplifier, the internal contact had failed coincidentally with my repair of the card.  Interestingly enough I had not even unplugged the T/R cable while repairing the card so it wasn't due to removing/reinserting the plug.  As they say S**T happens.

Good luck with your next project and come back to the Valiant soon!

Well.....here I am again!
BUT....this time I've got good news.
After a year and a half I think it's fixed.
It's been working for 6 months now and looks like it's gonna hang in there.

Just to refresh the memories without reading the whole gnarly thread again......
This transmitter had never worked...ever...from 40mtrs on up.
It worked fine on 160/80mtrs.

I determined that the multiplier was not multiplying the VFO signal for 40mtrs on up.
Just to jump to the chase and leave out all the crap that I did......here's the deal.....

L15 is mounted on TS6. This inductor is shorted by SW3-A from 40mtrs and up. I determined through very close visual inspection that L15 was installed too close to the other lugs on TS6. In fact, one of the other lugs was bent slightly and was touching the L41 end of L15.
This did not affect the multiplier on 160/80mtrs because the multiplier does not multiply on those bands.
BUT....this condition obviously detuned the multiplier enough to throw it completely out of resonance for 40mtrs and up.
I had previously grid-dipped it and it was nowhere resonant on any of the bands other than 160/80mtrs.
When I corrected that lug the tx worked on all bands for the first time in more than 50 years since it was built.

SO.....that's the rest of the story....and the end of the story!

Thanks to all for your help.

73

Congrats on nailing that tough dog problem, Dave!

Dave,
Doesn't it feel good when you nail the problem!  Then when you find it you say, "why did I not see that earlier".  All of this stuff is a humbling experience!

Congrats on sticking with it. Folks with less character would have flipped it on E Bay! 

Joe, W3GMS 

Johnny and Joe....thanks for your nice comments!
I had set it aside and let it smell bad for about a year until I discovered that the bench was getting weak.
In that time I had taken to heart what Tom had said in the quote.
I looked over the schiz closely and put the maloit on that dadgum choke and spotted the problem almost immediately....like 20 seconds or less. This problem was virtually invisible so I'm not surprized that it had not been found.
Having retired from AT&T and NORTEL, I have a long history of finding componant level ckt problems like this....I can tell you though that I was getting a bit desperate.

Thanks

73

If this transmitter was a KIT you can expect anything, something tell's me it never did work on the higher bands. And that maybe the reason it was never used much.

John W9BFO

We got one a few years back that did not work on AM.  Opened the rig up to find there was NO modulator installed. Ever.  Nothing. empty holes. I guess the builder was CW only :(

C

I had already told you several times that it was a KIT and that it had never worked on the higher bands.
This is not a POS radio....whoever assembled it did a great job....but made a slight mistake.

This was a hidden problem so while I have the rig out of the cabinet again I thought I would post a picture or two of what and where the problem was.
This rig worked only on 160 and 80mtrs....the rest of the bands had no drive because the multiplier was not working. Please read the details above and compare to the pictures. the nasty looking black choke is L15.