[Johnson] Johnson Viking II repair

[Mitch]

All, 

                Hi, my name is Mitch KJ7JA, and I have acquired my first
Johnson transmitter that is in need of repair that I plan on using as the
basis for a future AM station. I have a Hammarlund HQ-150 that I will be
using for the receiver. First let me say, I am a noob when it comes to these
old transmitters. I do have some tube gear experience, and am fairly capable
at troubleshooting and repair. I am also very careful when working around
high voltages and have all the necessary HV probes and other necessary test
gear to make this all happen. But I have started down a new road, and joined
this group to hopefully gain some insight and possibly give something back
to the group. 

 

Anyway, here is where I am at. While going over the Viking, I noticed a few
things that are not correct. First off, one of the original filter
capacitors has been removed. Fortunately, they left enough of the original
wire to figure out where to hook the replacements. I have already purchased
a complete cap kit, so that is on the list of things to do. 

 

The big HV resistor (R-13) appears to have been damaged somehow, and a PO
used a piece of metal and a spring as a jumper over the bad section. I have
not removed it yet, but it says on the resistor that it is rated for 35
watts. I did a little math using the plate voltage and the 20K ohm rating
from the manual and came up with approx 20 watts for the amount of power the
resistor dissipates. I have already located a suitable replacement that is
rated at 50 watts. It is physically the same size as the original, so it
should work with no problems. The attached picture shows the damaged R13

 

There is another resistor that shows some damage, but this one is from heat.
It also does not look like it is original equipment. I will be sorting that
issue out too. 

 

But before I put too much effort into replacing things, I will be checking
out the transformers to ensure they are not burnt out. The fuse in the ac
line is blown. The plan is to remove all the tubes, and using the VTVM,
compare the resistance reading across the various windings to what is listed
in the manual. If that all checks out, I will apply power through a metered
variac and apply voltage and see if anything doesn't look or act right. Then
once it is up to full voltage, I'll check the ac output of the transformers
and again compare them to what is in the manual. I do fully realize that
there is lethal voltages exposed while it is powered up. 

 

Anyway, I plan on taking the circuits back as close to factory as I can.
That way, I know what I am starting with and it should make it a lot easier
to get it back on line. From a cursory look, there does not appears to be
any mods, other that the repaired resistor. 

 

Anyway, thanks in advance for any and all help.

 

Mitch KJ7JA