[Johnson] common problems / upgrades for a valiant.
Singley, Rodger
rbsingl at ilstu.edu
Sat Nov 7 07:51:15 EST 2009
Hi Chris,
A great transmitter choice and it was my novice transmitter when I got my license in 1975. I currently own two Valiants and recreating my Johnson Valiant/Hallicrafters SX-101 novice setup was what started my current collection of vintage gear.
The following is a description of my advice for the Valiant. But most important, be very careful around these rigs. Be cautious and safe with the voltages present.
Below are a number of things to check on your Valiant to hopefully avoid later issues:
Most important! Before you turn the Valiant upside down to work on it loosen the screws on the insulating coupler in the VFO drive assembly. Otherwise it is likely to break and since it is non-standard (different input and output shaft sizes) you will either need to find a part from another Johnson rig (Rangers, Pacemakers, and 500's use the same part) or fix your broken one. The coupling tries to support the front panel in an upright position and it is not strong enough to do so.
The other thing you MUST check on early Valiants is the wire used for the filaments of the 866A rectifiers. Regular hook up wire was used on the early models and the insulation isn't sufficient for the HV that appears on the wire. The result is that the wires either short to each other and/or to ground and take out the LV transformer in the process. Either sleeve the wire or replace it with teflon or if you are using SS HV rectifiers then disconnect the filament leads and run a wire from the cathode connection directly to the HV choke.
If you haven't replaced the dropping resistor for the 0A2 in the VFO you should do so.
You will want to do the resistor upgrade fairly soon in the VFO. The resistor tends to go up in value cooking itself and the 0A2 socket in the process. In extreme cases it will also damage the phenolic circuit board. I would replace the 6AU6 while you are in there just to avoid doing that again in the next few years. Although some people mount the new resistor outside of the VFO it does stabilize faster with the resistor inside the VFO box.
Kit built Valiants often have highly inaccurate meter shunts. They consist of a very short piece of nichrome wire and the builder was expected to end up with a very precisely cut short piece of wire excluding the tinned portion which was more precise than most people could measure. In most cases, the shunts ended up too long causing the meter to read higher than actual. If yours was factory built then the shunts are almost surely OK and I believe in later kits Johnson included pre-cut shunts to avoid the problem.
The only shunts I would be concerned about are those used to measure final and modulator current. Do keep the final grid drive to 8 mils or less; early Valiant manuals specified a higher amount but the 6146 tubes are easily damaged by high grid current. 2.5 mils each (7.5 total) is fine for the Valiant-anything over 4.5 mils per 6146 is likely to damage the grid. But the grid shunt would have to be way off to get you in trouble.
If you do replace the shunts, standard .2 and .4 ohm shunts (should be available from Mouser) are fine. Don't worry about the missing .002/.004 ohms since the basic meter movement in the Valiant wasn't that accurate to begin with and 50 years later it won't have improved :)
If you have an early Valiant, low output on 160 is likely to be due to the plate coupling cap being too small. The earliest Valiants use a 500 pf cap which is far too small for 160 and later units use a pair of 1,000 or 1,200 pf caps in parallel.
The "turnstyle" type cap used for fixed loading is also a problem and prone to failure. If it fails you will notice unusual behavior with the coarse loading control. I replaced this cap in one of my Valiants with the "snubber" type dipped mica caps available from Mouser. Several people advocate replacing this cap with doorknobs which are fine but I think are overkill at the Valiant power levels. The only case where you would likely hit extremely high currents in these caps would be if you tried to directly load a very low impedance antenna on 160. Of course if you go through a tuner it would not be a problem.
Johnson says it is OK to switch the coarse coupling with HV on but I really don't advise it since the switch contacts don't like being hot switched. Once you tune it up the first time it is easy to preset the controls for subsequent operation and during initial tuneup I would drop the HV each time before increasing the coarse loading.
On the early model Valiants the roughly 30 mils that flows through the VR tubes also shows up on the plate current meter and confuses the power input issue. Johnson released a bulletin (it is available on BAMA) addressing this and suggested loading to an indicated 360 mils on AM for the early units; later ones should only be loaded to 330 mils since it is reading the true final cathode current for these rewired units.
On your model, I imagine the resting current for the modulator and final (for SSB) are set via sliding taps on the bleeder resistor. Be careful to thoroughly loosen those taps before moving them because the resistor wire is very fragile. Late production Valiants (and those modified for use with the Johnson 6N2 transmitter) have a modified bias network and idle current is set via 2 pots on the side of the chassis. Either system works fine (I have one of each) and there is no reason to do the update unless you buy a 6N2 transmitter to go with your Valiant.
The two wire, two fuse power cord is an area of controversy with the Valiant. It is bad practice to have a fuse in the neutral side of the line (and a violation of the NEC). For safety I would suggest either replacing the cord with a grounded 3 wire cord and a proper size fuse (could be added inline under the chassis) or if you want to keep a two wire cord do the following: First, make sure your AC outlet near the Valiant is properly wired (neutral is the larger blade). Then mark the Valiant power cord as to which side will always be plugged into neutral. Replace the fuse in the neutral side with a 20 amp or 30 amp fuse and be sure and use a properly rated fuse in the other side. No matter which method you choose, the old adage of ground is the first wire to be connected and the last wire to be disconnected should be followed.
If the dial drive is stiff or "crunchy" you need to clean and re-grease the ball reduction drive. To get it out, remove the VFO knob and the two small knobs on the VFO escutcheon. Under the small knobs are a pair of nuts that hold the escutcheon in place. Once you have it off you can remove the reduction drive by loosening the set screws. The two case halves of the reduction drive screw together and hold it over a clean cloth to catch the bearings if they fall out (which means the grease really dried up!). The bearings are standard size in case one gets away or they are damaged. Two similar reduction drives were used, one uses an actual ball bearing for the end thrust element while the other has the ball machined as part of the shaft. Clean the old grease off (WD-40 works well for me) and dry the assembly before using new grease. I use the same synthetic grease I use for the ball joints on my pickup and tractor. The grease should hold the ball bearings in place while you put it back together. The only trick is putting the proper amount of tension on the ball drive; too tight and it will be too stiff and too loose leads to slippage. You have a fair amount of leeway and it is easy to readjust if you get it wrong the first time. The drive is very smooth when working properly.
I added inrush limiters to both transformers on my Valiant and if you want to get rid of the Valiant "bong" sound then an inrush limiter on the plate transformer will take care of this noise.
One last thing comes to mind. If you run it on CW you might notice a bit of chirp on 40. This is from RF getting back into the VFO since it is on the same frequency as the final on this band. (the same is true on 160 but I have never seen the problem there). To avoid this, the VFO screws should be tight as should the fasteners holding the VFO to the chassis. Some of the Valiants (and Rangers) have a fairly large slot where the tuning shaft goes into the VFO and for these you may have to use shielding tape to close off most of the slot. Extreme cases require grounding the shaft where it goes into the VFO housing via a conductive "finger" or a flexible copper braid. There doesn't seem to be a lot of logic to this problem. One of my Valiants was fine on 40 while the other had a severe chirp. My Ranger 1 that I use with the Desk KW does fine on 40 but my Ranger 2 chirped on 40. My Viking 500 uses the same setup but it is fine. So hopefully you are one of the lucky ones not to have the chirp. It is only noticeable on 40 AM if there is hetrodyne interference but in for a bad case it is very obvious on CW.
If hum shows up on the carrier that is also present in the spot position then heater/cathode leakage in the keyer tube is the most likely cause. The Valiant (also the Ranger and 500) are very sensitive to this tube problem. There was a wiring mistake on the early factory built Valiants and if it turns on the HV in the spot position then you need to rewire the switch to agree with the schematic (which is correct). You would think they would all be corrected by now but I bought one at Peoria 5 years ago that was still wired this way.
Before you rip out the clipper circuit, be aware that minimum clipping occurs with the Clipper control set to the full clockwise position. Although it is intuitive to turn the control to fully counter clockwise this is actually maximum clipping instead of off and the audio will sound horrible. Although the Valiant provides healthy output there are times when the ability to dial in a little clipping makes the difference between easy and no copy for the receiving station. I will admit I prefer keeping my old rigs as stock as possible.
73, Rodger WQ9E
-----Original Message-----
From: johnson-bounces at mailman.qth.net on behalf of w1cjf at verizon.net
Sent: Fri 11/6/2009 11:35 PM
To: Johnson at mailman.qth.net
Subject: [Johnson] common problems / upgrades for a valiant.
How is it going? I am chris and i am 28 years old from rhode island. I just picked up a absolute drop dead sexxy valiant from a local on craigslist. I am the 3rd owner as the previous one was given this valiant from his uncle who bought it new, as a kit it looked liked to me. As every tube along with other markings on the case for what does what. All notes were done in pencil. As i am going through it now cleaning it up and stuff, i am wondering what common problems do I need to be made aware of so i can take care of them now? I have heard of something with the band switch but i am not certain what the problem is and the fix for it. This has the STOCK tubes in it and has never been re-tubed. This is the first thing i am going to take care of, along with the power cord which the shielding has fallin right off of the cable itself. The caps are not leaking which is a good thing i guess, but i think i will need to change them down the road. I know I am young but i just love these
damn things, I have had offers to trade it for a newer style radio ie a 746 PRO but it will never happen. My uncle is helping me with this project since he knows alot more than I do. The paint on the front of the radio is dead sexxy, i cleaned it up tonight and it looks like it just rolled off of the factory minus 2-3 very small nick's but other than that all the screen print is 100 % intact. It also came with the original owners manual which has a lot of info in it. Here is a link to my album of pics of it so far from the previous owner, I will get pics of the state it is in now next time I goto my uncles and start working on it again. I know that this mailing list will be very useful me and there are a lot of great members that are apart of it.
http://s47.photobucket.com/albums/f154/plasmablue636/Johnson%20Valiant/
73's
chris
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