Just powered up my Phantom 19. It works great on AM across the entire band. And it works great on the 2 higher short wave bands, at least on the top half of the scale on each band.....but when I tune down below about half way on these SW bands I hear a popping sound that sounds like popcorn popping.

I bought it in recapped status but the replaced electrolytic caps in the power supply look old.

Any ideas?

Joe

Maybe there is dust in between the plates of the SW tuning caps?

But AM uses the same tuning cap as SW bands and it works fine on AM?

What does it sound like in terms of speed/frequency?

You sure its not more like a motorboat sound ?

Actually, that's what they called it back in the day-"motorboating". It's a kind of feedback. It can be a low tone or put-put sound or a higher pitched whistle. It might be caused by poor filter capacitors, lack of tube shirlds, wiring that had been moved around. etc.

-Dennis

Check all the previous work that was done and make sure none of tha parts used are those prone to failure.

Shut it down. You probably have an arcing capacitor, less likely a defective tube.

This is usually caused by a bad filter electrolytic, you can jump them with a good one to check.

Dave

What about single loud intermittent pops? I have this with my Scott 15 and cannot locate the source. At one time, I thought it was from a dirty tube pin but cleaning pins and sockets does not fix it.

I used to get that on my Electrohome 6v6 amp, when i recapped it i didnt get the components in exactly the right spot, i had to go over it and move some wires around and i also covered some leads in heatshrink tubing, hasnt done it since.
The motorboating sound tends to get faster if you increase the voloume, if this is the noise hes getting then its interference, he needs to go back and check all his leads and make sure they run properly.
Im still learning myself but ive learnt lots from these guys, mind of information.

Your Scott is popping corn? Where's the salt and melted butter

It may be an idea to give us a look at the caps that are currently in it. Why I say that is that I have recapped a few sets that have been done before, but in the era when paper was replaced by paper.

If it's only happening at the higher frequencies It has to be some thing common to them. Oscillator tubes normally fail at high frequency. This can also be (and often is) related to them switching in faulty components, or running low on voltage due to high resistors. Also check the tube shields, where fitted (or missing).

As said the "Putt Putt" is motorboating, which is feed back or other forms of destabilisation.
"Snap Crackle & Pop" are more likely (when not back in their box) the realm of switches & Mica caps (often the ones with B+ on them).

Lead dress cannot be overlooked since it has been worked on.

Marc