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Author Topic: Johnson Valiant 2 Transmitter  (Read 7531 times)
KA4KOE
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Posts: 317


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« on: October 29, 2007, 01:05:42 PM »

I am about to become the proud owner of a Johnson Valiant 2 transmitter, already checked out and tested. Anything I should be aware of from the collected knowledge of the gang here?

Thanks

Philip
KA4KOE
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WB2WIK
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Posts: 21753




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« Reply #1 on: October 29, 2007, 03:14:18 PM »

Wear a back brace when you pick it up.
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KG9SF
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Posts: 280




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« Reply #2 on: October 29, 2007, 03:19:39 PM »

I'd suggest warming up the rig for at least a half hour before using it.  The VFO needs time to cook or it will drift.  You might want to solid-state the LV and HV rectifier tubes to keep the heat down inside.  There are lots of articles on how to do it.  I solid-stated my Ranger by replacing the 5R4 and the 6AX5 with diodes on a perf board mounted on octal tube sockets from burned-out tubes.  Or, maybe the Valiant 2 already has solid-state rectifiers, I'm not sure. You should really enjoy your Valiant. Are you going to use it on AM, SSB, or CW?
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KA4KOE
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« Reply #3 on: October 30, 2007, 05:14:45 AM »

Primarily AM. I think you need an outboard unit to run SSB and I don't think thats part of the package. ITs pretty much FREE as I did a favor for someone.

PHILIP
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W5RKL
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Posts: 1032




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« Reply #4 on: October 30, 2007, 08:12:10 AM »

"Anything I should be aware of from the collected knowledge of the gang here?"

Yep, there sure is.

1. The Valiant uses high voltages, voltages that can
easily KILL you. If you have never worked around high
voltage then I highly recommend you learn from someone
who has before you venture inside the Valiant.

2. Learn about Mercury Vapor Rectifiers (866's).
If you don't, you could end up with more problems
than you started with. They can be substituted with
3B28's. If you simply substitute the 866's with
3B28's and not learn why, you've not learned a thing!

3. Without even thinking, replace ALL electrolytic
capacitors if they have not already been replaced.
I do not use NOS capacitors, especially in power
supplies. For those who do, more power to you. I
use new capacitors!

4. Change the 2 prong power cord to a 3 prong grounded
cable. Make sure the "BLACK" wire is wired to the
fuse, not the WHITE wire. "BLACK" is the HOT side of
AC. Use the proper wire size as the Valiant draws
"500 watts" at maximum output from 120VAC wall outlet.
A cheap computer power cord cut to fit is too small
wire gauge.

5. If you modify the power supply to solid state
diodes, take the safety precautions to protect the
diodes. Also read up on how diodes verse rectifier
tubes can increase the power supply output voltage.
Solid stating a power supply, whether it's a high
voltage supply or not, can affect other components
in the Valiant. I never trust anyone who says, "I've
solid stated my transmitter and it works fine and
I've never done those things." Modifying from tubes
to solid state diodes will reduce the heat, that's
true but it's not that simple.

6. Learn about choke input filters in power supplies
so you know what happens to diodes that are not
protected. A lot of vintage transmitters use choke
input filters in their high voltage supplies.

7. NEVER apply power, whether through a variac or
otherwise, before performing a thorough visual
inspection of the underside chassis. Looking for
burnt, cracked, or otherwise failed components.
If bad components are found, find the source of the
problem BEFORE replacing the component. Some failed
components are due to age but some may not. Fix
the source of the problem FIRST otherwise you'll
be replacing the same component before you know it!

8. Any burnt wiring should be investigated to find
out why the wiring is burnt. It may be just a person
who used a 150 watt soldering pencil but then again
it could be a short somewhere that caused excessive
current to flow. A tube that is shorted internally
can cause excessive current to flow, overheating the
wire. Same applies here as in item 7 above, find
the source of the failure FIRST before replacing the
component!!

9. Clean ALL switches with a good quality contact
cleaner. Wait the required time BEFORE applying
power otherwise you could cause your nice vintage
piece of gear to catch fire. Most contact cleaners
are flammable and have a warning label. It's there
for a reason.

10. NEVER attempt repairs without the schematic.
If you do not have the schematic and/or manual
then get it by either downloading from various
websites or buying one from one of the many ones
available on the Internet.

This may think this is a lot of work and some may even
think it's overkill. For new hams who are not familiar
with vintage gear, it is. Vintage gear is not "Plug
and Play" like todays ham gear. They do require work
and circuit knowledge to keep them going.


73's
Mike
W5RKL
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K8AC
Member

Posts: 1762




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« Reply #5 on: October 30, 2007, 09:27:14 AM »

I second W5RKL's view on replacing all the electrolytic capacitors, especially if the originals are still in the Valiant.  A defective or failing filter cap can take other components with it.  Don't be mislead by the fact that the Valiant may appear to work fine with the old caps.  

73, K8AC
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K3HVG
Member

Posts: 149




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« Reply #6 on: December 26, 2007, 04:38:57 AM »

This reply may be a bit tardy, to be sure, but hopefully you've also changed and moved the 18K VFO screen resistor.  If you need the particulars, please drop a line to K3HVG.  Be happy to send the mod to you, plus all the others that are considered good or necessary.
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W0EAJ
Member

Posts: 29




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« Reply #7 on: January 22, 2009, 07:36:57 PM »

What you've already read is spot-on.  When replacing the electrolytics, note that those for the bias supply are REVERSE from the others (+ to chassis).  I recently fixed one that was backwards.  Also, anybody who wants to replace the escutchion gasket on the VFO cover - go to www.fourmost.com and select "cockpit coaming - Large" p/n FOR-120.  It's split rubber that fits the edge PERFECTLY, and is better than original.

In addition to replacing the electrolytics - also replace the bypass caps with "orange drops" from MOUSER.  They'll outlast YOU.  

Careful of the VFO shaft coupler - they become very fragile after a few decades, and are made of unobtanium (you'll have to MAKE one, if it's broken).  

Replace all of the parasitic suppressors - they may look okay, but most likely... aren't.  Tighten all hardware (kit versions always seem to have loose screws - like the original builders), but be careful not to exceed torque on the ceramic insulators.

Replace the 18K resistor in the VFO cage - typically, it's WAY out of tolerance, and is too small - buy the Vishay 5w versions from MOUSER.

DO NOT USE 6146B or 6146W tubes, vice the 6146's - this thing was designed for the straight 6146.

The 6BY5 bias rectifier is tough to find - use a pair of 1N4007's with 10 ohm / 5 watt resistors in series with EACH diode... stick it in an old tube base, and fabricate a cover from a pill bottle cap or something.

Tom
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