The AM Forum

(https://i.postimg.cc/5QSVYFyJ/Viking-Valiant.jpg) (https://postimg.cc/5QSVYFyJ)
So this followed me home from the Montgomery AL ham-fest Saturday. What mods to the audio are the good ones?  I have read comments all last night and this morning, and I would like to get the opinion of this forum.  OR -- do I leave it alone and plug in a mike?

Mods to the audio would be the last thing on my mind at this point. Get it up and running, see how it performs electrically, get it on the air for awhile, and then decide if any mods would be required for the transmitter.
Ya never know, but it might be a complete dog  :)

The first thing on your list would be the infamous Chernobyl resistor R3 in VFO box. All the old electrolytic caps need to go or they will on their own. Other than that see if any smoke comes out.

Get some lollypop sticks and make some pointers for the knobs.

I wouldn't replace any electrical components until you determine the mechanical and electrical integrity of the entire transmitter on all bands and modes. I've seen too many people get a rig, replace all the caps and other componets, maybe even do a mod or two, without first determining if there are some initial problems before you even started any component replacements. Then, after all the replacement stuff is done, you power up the rig and it doesn't work properly or at all. At this point you can't tell if it originally came not working or you did something wrong when doing the replacement stuff.

Was the transmitter factory wired or built as a kit?
 

Definitely fire it up and ascertain "normal operation" first.

Then look under the chassis to see what was done to it.
IF the 6AL5 tube is not in place, likely someone did the "usual"
mods to the speech amp. Which is good.

One thing to consider is to take the 120vac off the PTT line -
replace the relay with a low voltage one. I put a small xfmr
and rectifier/filter board to power mine.

Two things to consider are sweep tube (or similar) modulator
tubes and a some sort of negative peak limiting.

                _-_-bear

The good news (to me) is, it is a factory built unit. Rivets instead of screws and nuts on the tube sockets. Plus, it is all original, the previous owner did pencil in the tube types on the chassis. The HI voltage rectifiers are 3B28's instead of 866's. From looking at the schematic, and comparing to the actual, I think it's 100% stock. Certainly I will get the dummy load, and fire it up, and see what smokes / or gives. :)

(https://i.postimg.cc/xJ9x3Krp/Valiant-6-top-side.jpg) (https://postimg.cc/xJ9x3Krp)

(https://i.postimg.cc/Bj1VSScp/Valiant-4-underneath.jpg) (https://postimg.cc/Bj1VSScp)

There are a few mods/repairs in there...

May I suggest that you post the pix directly here on AMFone and not on
a 3rd party site? Those go away, so anyone reading the posts later will
not get the benefit of seeing the images!

It's really important to bypass the clipper circuit entirely.

Basically that's a cap between the plate of the preceding tube and
the grid of the following tube, disconnecting the end of the LC network
that goes to the grid, and taking out the clipper tube.

                      _-_-

hi Bob ... nice score there ... Tim did a very good writeup for the Valiumhunt a while back .... suggest you readit before you start the mods ... 73. John

Bear, please point out the mods or upgrades, so I can relate them to the actual unit. I found a great write up from Wireless Girl on the internet that goes into great detail on mods and when not to mod. I can bypass the clipper, as I will be feeding line level audio in from a broadcast microphone processor.

I am printing off the article Tim WA1HLR wrote on the Valiant. This will be my plan, once I hear it on the air first, to ascertain it is modifiable!.

Hi Bob,

Nice looking Valiant!   Good way to start out.

I was once out on a friend's yacht and axed him how much I'd have to pay to get something like this. He said it depends on how much work you want to do.  He then pointed to a partially submerged, rotted, wooden boat near the shoreline.   $1 will buy that one.

So I'll say the same thing... depends on how much work you wanna do on that Valiant.

Here's a guy who took it to an extreme. And you can too, over time.  Compare his pictures to your stock ones.  Since then he has added even more bells and whistles, like a MOSFET audio driver for the quad sweep tube modulators.  His own homebrewed oversize modulation transformer.  Notice the four 6146s.

Tom, K1JJ


Frank WA1GFZ's super Valiant:

http://amfone.net/Amforum/index.php?topic=43762.0

Here are some upgrades I did for a friend not too long ago:

Phil - AC0B

I think the article attributed to Tim may be "ghostwritten" based on things he said.
Not sure.

I saw fresh caps and it looked like the xfmr on the right side bottom of the chassis is
not stock... nothing radical, just that it looks like perhaps it was worked on...

The only way to determine if modifications were done is to download the Valiant schematic and check the current wiring against the unit you have.

Phil - AC0OB

Some things to consider....

The tube sockets being riveted in....after 60+ years there will be some amount of galvanic corrosion.

Corrosion on the tube pins, and on the socket pins. Some socket pins may have lost tension to clamp the pin.

Grounds may not be grounds. Chassis pieces bolted together might not make a good full contact ground.

The paper inside the transformers might be disintegrating. Translation, failures are a coming down the road. Might be possible to bake them out (topic in itself), and then vacuum impregnate the transformers (covers off) with transformer varnish. This would be followed with another bake out appropriate to cure the varnish. Not long ago I had to replace the wires on a Viking II modulation transformer because the cloth insulation was falling off as the wires went into the transformer wire holes.

I would be leery of any mods until victims from age and moisture have been sorted out. Even transformer lamination's if rusty will have an impact. In a filter choke, this could lower the inductance, and in any choke or transformer, there could be noise, or modulator talk back.

Jim
Wd5JKO

Phase two, I have changed out the HI V filter caps, and all four 15 mfd. caps in the low voltage section. I inspected the wiring, and believe this unit was treated well as the wiring covering was still soft cloth, no flaking, the plastic coated wiring still retained the original color, and no burned resistors were discovered.
With that accomplished I installed a 3 wire power cord, and fired it up. No smoke, no sparks, no flashes. Tonight i got my cantenna and a length of RG8 and printed off the initial operating instructions. To my amazement, everything came up perfectly, the figures in the Johnson manual, were easily achievable with this Valiant, so I got real brave and loaded it up in CW mode, and bingo, I tuned it up to 400 ma in CW and everything is fine. I cannot believe my good fortune.
I will need a replacement bulb for the "plate on" indicator, but otherwise, I think it is air worthy, but I will repeat this procedure about 5 times tomorrow, and make sure it is solid.
I certainly appreciate all the sage advice from the contributors.

By the way the Tim WA1HLR article I found in the AM Window, Tech Mods, Valiant.

It's kind of like renovating a house...  wait a year.

My Valiant was fully restored by Chuck Hurley and he only does "stone stock" and in my view its pretty good, as is. just turn the audio compression off, as mentioned it's a joke.

John 73 W1JTO

I appreciate that thought John, my years in broadcast taught me to never assume anything good, it will probably change!

Happy Thanksgiving to everyone. 73

I'm with the "keep it stock" crowd.   

The engineers at Johnson knew what they were doing.   EFJ sold over 56 thousand transmitters of several designs in their day.

I purchased mine from a friend who had used it for ten years or so, and I've been using it for over five, and it just keeps running rite along.   If it works, what's to fix?

I use an external audio chain, class D amp and a pair of Antek transformers with the primaries tied together as a modulation transformer. Remove the modulator and audio tubes from the rig and leave it stock. Use the 9 pin socket on the back to bring HV to the modulator and modulated HV back to the finals. A modified Heising modulator with the Anteks at the heart of it all works FB. I believe AB2EZ was the first to do this. W2VW was the first person I heard using it and W2BTK broke it down into simple math that even I could understand. A schematic is on his QRZ page. It has worked well for me with a Johnson Ranger and a Valiant.

73 de AG5CK

Great Find, Bob.

Somewhere on an old computer, I have an article on replacing that inter-stage audio transformer with a phase splitter based on a ( I believe )  Gibson or Fender guitar amplifier design.

I wish I could find it.


Don W4DNR

From what I have read from various sources, the Hammond 124 B or E is a good replacement, and good frequency response.

If you are referring to Interstage transformer T4, the one most used is the Hammond 124D.


Phil - AC0OB

It's kinda like a classic car or any other antique or work of art. Why would you want to chop it up? If you are really that dissatisfied with the design perhaps perhaps home brew from scratch. I restore antiques as a hobby and go to great lengths to use the proper finishes on wood. Such as colored lacquer not stain and modern polyurethane. It would be convenient to use a modern finish but it wouldn't be a restoration it would be a customization. Perhaps I am being persnickety or just a crabby old man such is life. Alas I will probably get flamed for my humble opinion.

Johnathan N8QPC

Jonathan, all opinions are appreciated, by me.  I restore tube era broadcast equipment, and I speak your language.  It should look original, and if possible work the it did when it left the factory. Only when I have a shell of a former classic piece with no "guts" (because someone realized that tube pre amps are gold on ebay) do I resort to a different path.The clipper seems to be well supported for removal, or in my case, by passed, no harm no foul, remove the jumper, replace the tube and "we're back". As for the driver transformer, the present tranny sounds really bad, so I am going to replace it, BUT, keep the original in case that ever needs to come back home. I plan nothing radical. I have heard it n the air passing music into a dummy load, and I think the driver  TX replacement will finish my mods. As someone posted earlier, Johnson knew what they were doing, but some cost provisions on an already expensive unit, may have caused them to take a monetary short cut on some things.

I have a 57 Chevy Bel Aire that looks "stock" but has improved suspension and drive train.

Is it the best of both worlds, or worst of both worlds ?

I like the *appearance* of stock radios. 

I'm going to replace the capacitors with newer/ better, but I'm not going to stuff old capacitor covers with new just to make the under chassis look like nothing was done.

If it looks good and sounds good, I'm happy.   

Don W4DNR

That sounds like a winner Don.  We will have to QSO soon.