Johnson Viking Thunderbolt

[kb2vxa]

Now you see the value of visual inspection, by scrutinizing What Is And What Should Never Be (a cool Led Zeppelin song) you isolated two problems, odd behavior of the VR tubes, and the open RF choke. I've seen plenty of 4 pie 2.5mH chokes, but never one sprayed with Cosmoline. That BTW is that brownish stuff that looks like spar varnish the military moisture proofed radios with. You wouldn't want to work on one with that gunk covering everything under the chassis, BELIEVE ME! I see the wire is blown open, melted on the end, but what made the pie become displaced when it was "varnished" in place I can't imagine. No big deal wondering how or why, all that matters is you need a new choke. No problem there, ePay is littered with them, 3 and 4 pie with and without Cosmoline. Oh, in addition to pushing the shorted wire off the socket connection opening the short I'd lift R112 well away from the chassis, it looks like a short waiting to happen. If there's one there is more, time for search and destroy, kill them all and let God sort them out. (;->)

[KA2PTE]

Ok Warren roger that. I did order a few new ones soon to arrive.

Was told that usually when these chokes go theres a bad HV tank cap somewhere. Since I replaced all the doorknob plate tank caps, set out to check C10 (0.001 / 2.5-5KV) and it was breaking down under load. So were the rest of the coupling caps that SW2 shorts out to help you tune up. Was wondering why I had to have it always set to MAX coupling to get 80m to dip. With the switch fully shorted, only had about 395pF max capacitance on the array. One was only wrapped on the switch solder terminal, no solder - and you could tell that connection was overheated quite alot.

So as these are obsolete, I am gonna use doorknob's because also the KV rating will be much overkill but that makes me feel ok because this is
now a modded amp, with 3400V, not the factory 2400.

I started dry fitting a bracket nearby the switch to hold the door knob caps, and it ought to work real nice, as the leeds will only be a little longer to reach the new location.

upper_.jpg

Theres also 1 new hole you can see now available on the bottom of the bracket because the old capacitor array was using it as a mount. Theres also another up higher in this photo - so I could place 2 more door knobs possibly, to add more coupling if I need to try and mod for 160m.

under_.jpg

So possibilities look good over there, however in the fan compartment where C10 is, its alot tighter, and it means I probably have to mount (2) door knobs in parallel to get 0.001 uF.....but its possible.

I believe all these caps that are shot probably contributed to the issue I saw as I was trying to load on 40m just before the choke blew. There was for sure not enough capacitance coupling, and C10 being almost invisible, probably does something bad for the tubes output plate capacitance by the looks of it.