How to track down bad tube and what can it mean?

Budrew, tracking down a sick tube requires a little patience and a consistent, methodical approach. Also, keep in mind that moving a tube can cause an intermittant problem to clear up for a while, but then return later.

First, pull and re-seat all the tubes to make sure contacts are clean and you are making a good connection in the sockets. Probably a good idea to clean the tube pins while you're at it, if you didn't do this originally. If the noise continues, try to narrow down where the problem tube is located.

From your description, you know the noise is in the left channel but you don't know if it is in the preamp or the power amp. If you have a way to resolve this, that would be a first step. For example, if you have a CD player or tuner with variable outputs, you could try plugging it directly into your amp to see if the noise continues. You would then know whether the problem is with the amp or the preamp.

If you decide the noise is most likely coming from the preamp, if it is a full function preamp, determine if the noise is in the phono stage or the line stage (i.e., do you hear the noise only when playing an LP).

Then try switching one tube from the left channel with it's matching partner in the right channel. Listen for whther the noise shifted to the right channel. If it did, that's the tube to replace. If the noise stayed in the left channel, switch a second pair of tubes. Switch only one pair at a time, and don't switch another pair until you've listened long enough to be sure you are getting consistent results.

Have patience and be methodical. Good luck!

If the buzzing continues to exist in one channel only, start by swapping each pair left and right until the distortion hops channels. Too tedious? You could always pay someone else to check it out.

Buzzing commonly indicates a faulty tube. Then again, there are some species of moth that like to nest in the tube sockets...

Take heart. Be patient. Keep telling yourself how happy you'll be once it's all sorted out.

The distortion appears to be caused by one of the new tubes. Replace the new tubes - one at a time - with equivalent older ones, listening to the amp after each replacement, until distortion disappears. This technique should allow you to identify the bad tube. Hope this helps.

I had this problem. The first thing I did waw to reverse my interconnects to see if the sound moved from right to left. In my case it did not so the problem was in the amp.

Next, I reversed all of my tubes in the amp to see if the sound moved and i did this to see if indeed the problem is a tube or some other connection. The noise moved.

Then it was just a matter of time as I traded pairs of tubes until the sound moved again. I nest moved just one of the tubes and the noise moved again. Bingo!