The Valiant is the latest (and probaly last for a while) piece of gear I picked up. It is also the heaviest piece of gear I own weighing ig at 83 lbs. I found it at the GSARA hamfest in Sept 2011. She's in good shape and clean. While it was fully functional it did have some AC hum on the transmitted signal which made for some audio distortion and a wide, dirty signal. The source of the hum was narrowed down to one of the three power supplies in the rig. I removed all the rectifier tubes, replaced them with rectifier diodes and replaced all the filter caps. I used 120 uF caps in place of the original 80 caps. Doing this cured the hum problem. While I had it open I also disconnected the audio clipper circuit and bypassed it. At this time I also removed the 1 meg resistor from the mic input of the rig and installed a 10 meg resistor in its place to match the impedance of the D-104 that came with it.


Full schematic showing rebuilt power supples (used 120uF, 450 v caps in place of the 80uF caps), bypassed audio clipper and added a 10 meg mic input resistor. Click to enlarge.



Old power supply components and clipper. The 3B28s were used in place of the original 866 rectifier tubes. Note: each 15uF cap shown contains two separate 15 uF caps for a total of four 15uF filter caps in the rig.


The Timtron Mods...

I have done all the mods as told to me by the master himself, Tim, WA1HLR. The audio section is much hotter now, has better audio quality and the rig has better modulation. The WA1HYellR Valiant mods are now available on The AM Window site here.

I was running a stock, unamplified D-104 with the Valiant but have modified the D-104 and installed a Radio Shack condenser mic in the head which, in my opinion sounds better than the D-104 element. I have gotten good audio reports with it.

As of Jan 7, 2011 the Valiant is still going strong. It has been in use almost every day since I got it last September.


Fan installation: As my Valiant is in rather tight quaters I wanted to prevent excessive heat build up. The fans came from a laptop chiller pad that I never used. As they were intended to be powered from a USB source they should require 5 -6 VDC to run. They run quietly and move a good amount if air.



Fan suppy circuit




Homebrew cover for the Acc plug. The plug had no cover on it when I got the rig. There are bare high voltage jumpers in this plug so no cover is dangerous! I fashioned a cover out of a base from one of the removed rectifier tubes.







Valiant Links...










Crusty Valiant tank circuit. The large plate choke, plate bypass caps and small plate choke have been removed as one of the bypass caps shorted to ground taking the small plate choke out.






All nice 'n shiney. Scotchbrite and a little silver polish did the trick.



It works better now that it's clean. The electrons now move smoothly through the coils without getting hung up in the crust (just kidding).



Shorted plate bypass cap...

One day while tuning the Valiant I heard a "pzzzzzf" and the plate current meter pegged full scale. It turns out one of the plate bypass caps shorted to ground which fried the small RF choke that's connected to it. This was easy to diagnose and repair. The damged parts are shown in the photo below.

Modulator static (idle) current issues...

From day one I had issues with the modulator static current being too high. It should be 50 - 70 mA but was up around 225 mA and could not be brought lower. I removed the meter shunt (small piece of nichrome wire), measured the actual current with two different meters and found the actual current to be 150 mA. The nichrome meter shunts in these transmitters are known to be somewhat inaccurate. I found the resistance of the shunt to be slightly higher than spec so I trimmed it until the front panel meter agreed with what I had measured. The static current was still too high but at least it came down some. Getting the hum off the audio by rebuilding the power supplies reduced the static current even further and I was able to adjust it to 60 mA with ease. I noticed that the current would drift around some and needed to be adjusted periodically. This situation slowly got worse and the current would rise and fall quickly at times like there was an intermittant connection or a dirty pot. It got to the point where it would not stay where I set it for more than a few seconds. and the adjustment pot became very "touchy". The pot used to adjust the static mod current, R62, should be a 5 K ohm pot. I found it to measure over 400 K! Disassebling the pot revealed the source of the problem, the carbon "traced" was cracked. The only pot I had on hand was a 10 K wire wound pot which was a little larger than the original but I managed to squeeze it in there where the original pot was. With the new pot the static mod current stays right where it was set and does not budge.

Operating the rig...

I fire this beast up everyday and run it on 10 meters during the day and on 75 meters at night. Overall I am pleased with the performance. Yes I've had to do a few repairs and mods to it but this is to be expected with a rig that is 50+ years old. I've been told that it sounds great and I'm getting 110 - 120 watts out on 10 meters and 140 - 150 watts on 75 meters. It runs good, looks good and I enjoy working on it. What more can you ask for?