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Old 11-20-2016, 07:37 AM
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Polaraligned Polaraligned is offline
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Location: Montvale, NJ
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Andrea T-VK12 -- Lightning Strike to Antenna?

I cleaned up this chassis real nice, and the cabinet is in super nice condition. Taking a close look underneath, I noticed what look like the signs of a lightning strike to the antenna input.
You see here what is left of the mica capacitor going from one antenna terminal to ground:


Then there is another blown up capacitor from the antenna input going to the AM converter. It is not shown on the schematic, but this looks like a factory revision. It is between the antenna terminal and L15.

Then there is L30, to the right of the capacitor in pic, is tests open.


Here is the schematic.



This set has me concerned because somebody took the safety interlock switch out, and installed a fuse in the line. The set is totally unrestored and sports all of it's original paper caps.
The HV cage cover and the HO tube were missing when I got this set. Of course, that has my concern up that there is a potential flyback problem.


Luckily, I have obtained another T-VK12 that had a basket case cabinet. The chassis in this parts set looks unmolested. It is an earlier serial number and does not have a few of the updates that the set in question has. I spent a lot of time cleaning the "lightning strike" chassis, so now I ponder whether to clean the parts chassis and restore that, or precede with this one that is clean and on the bench. Of course, I can swap parts as needed, but it is always better to start with the best set possible.

The set is loaded with those HI-Q ceramic tubular capacitors. I assume they are fairly reliable, as are most ceramics. What would be a good replacement for these? I know the temperature coefficient is very important with ceramics. Of course, I will only replace as needed. I have no plan on shotgunning those ceramics.
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