These are pictures from one hell of a hard transmitter rebuild back in 2004. The transmitter was an old MK-12 from Energy Onix that had been neglected for years. The owner thought he could save money by hiring some local HAM operators to "fix" it. They pretty much destroyed the transmitter and it took us quite a while to undo all the damage by the so-called "techs".
Needless to say, this MK-12 transmitter was DOA when we got there. And is it really any wonder when you examine the picture. What a feat of engineering skill we saw when we opened up the RF cavity.
Using vacuum caps on a FM transmitter is a nice touch and one I don't think I've ever seen before. I couldn't believe my eyes! They replaced all the copper straps with brass ones with no thought as to the fact that the copper straps were inductors. What were these guys thinking? Answer: They weren't.
One can only guess at how much spurious noise this puppy was pumping out over multiple bands before it blew up.
Using vacuum caps on a FM transmitter is a nice touch and one I don't think I've ever seen before. I couldn't believe my eyes! They replaced all the copper straps with brass ones with no thought as to the fact that the copper straps were inductors. What were these guys thinking? Answer: They weren't.
One can only guess at how much spurious noise this puppy was pumping out over multiple bands before it blew up.
Blown out tune inductor. Is it any wonder with all the mis-match of parts that they had in this poor thing! One can only imagine what kind of current this was pulling when it went BANG!
Now this really scared the crap out of me. That's the fixed load inductor they were using. Seriously? Someone actually thought this was a good idea? Man oh man....
We also found the RF filter turned around backwards and we were told that someone from the "tech guys" that were there before us pulled it apart and cleaned it with steel wool pads! Really?
These things are tuned at the factory and are not meant to be pulled apart and "cleaned". No wonder there were several RF arc burn holes right through the copper pipe. Since you can't just run out and buy one of these guys, we ordered a new one right away.
A look at the inside of the RF output directly above the PA box. Look at the arc marks. Now this wasn't from lightening damage. This was caused by all the crap the so called "techs" did in "fixing" the transmitter. You can see a brand new inner copper pipe in the background. The old one was so damaged it had actually melted from the RF heat. Also, all the bullets were so badly damaged that they needed to be replaced.
The new filament transformer and coils as we were installing them. The old transformer had been damaged by the "repairs", and the "tech guys" had removed the old coils and threw them away. Once we got these in place, we bolted down the transformer.
New 50 Pf plate blocker caps installed on the new fixed load inductor. The 3cx10000a7 tube may look like it got pretty hot at one time, but it was working well enough to test the transmitter at low power before replacing it.
A new fixed inductor installed. Energy-Onix wanted an arm and a leg for a new one, so we designed this one with a $5.00 piece of copper from Menards. It worked better than the old one that had been destroyed by the "techs".
Completed PA cavity. New 50 Pf blocker caps and strap to the transmitter load and tune inductors instead of those lovely vacuum caps and brass straps.
The rebuilt transmitter came right up under low power (4.5Kwatts) and only took a few minutes to dial in before bumping it to high power (12Kwatts).
A little more tuning and this ol' 12Kwatt transmitter was putting out 14.5Kwatts. 2.5Kwatts more than it did when it was new. We only needed 10.5Kwatts out to meet the ERP of 35Kwatts.