Tube amp blues

I'm sure that there is a simple explanation but being new to tubes I just haven 't learned it yet. When I turn on the amp it starts with no problem and plays wonderfully. After about 3 - 5 minutes it starts making a "static-y" sound from the right channel. This is not constant, it comes and goes about every 10 to 30 seconds and there sometimes is white noise between the louder static-y sounds. Both sounds (Static and white noise) come at different levels sometimes louder than others. Sometimes there is no "static-y" sound at all and all is quiet, just great sounding music. I have done some checking and this sound does not respond to any of the other equiptment. Only the amp needs to be on for it to happen. When the whole system is on there is no difference in the noise. I have played music from my CD and Turntable at different volumes and the noise is not affected. I have found nothing that can be done to stop the sound or make it worse except turn off the amp. It only starts after the amp is warmed up. Could this be a bad tube? Or a bad component on the board that is causing this after the amp warms up? Any Idea's.

Thanks Rick
All I can suggest is to swap the tubes between channels, to see if it goes away. It could certainly be a bad or microphonic or old tube, but could possibly be something more. I'm sure someone with more knowledge than I will respond shortly, but this may get you started... Good Luck!
Richard- Since you didn't detail that the noise was specific to one channel, I'll assume that it is occuring in both channels. With that said, swapping tubes from one channel to the other may not provide any further insight into the problem. However, swapping or just reseating the tubes will tend to "clean" the tube pins and socket contacts which is highly advisable. Not knowing the particular amp, I can't offer much more than the tubes may need replacement. I would start with the small signal tubes first, before replacing the output tubes simply because of the cost associated with them. FYI- New Old Stock (NOS) tubes are usually preferred sonically, but can greatly increase the cost of retubing. Output tubes are best acquired in matched sets to help insure longer life, maximum power output, and hopefully equal aging characteristics. You might also consider having a few spare small signal tubes on hand that are known good, to help in the troubleshooting efforts. Goodluck.
You must swap tubes with some different ones! Start with the driver stage tubes (the small ones) . Then sub out the power tubes. Most problems will most likely be tubes. Sounds like the tube gets noisey(common) when warmed up.If you do not have extra tubes now is the time to get them. You will use them anyway if it is something else. Only after absolutely ruling out tubes is it time to look elsewere.
Sometimes swapping tubes (same tubes different channel) in a preamp solves that problem, it has to do with gain, not sure about power amps but worth a try. Good luck.
Hi everyone and thanks for the ideas so far. The unit is a Golden Tube Audio SE-40 and the noise is only in the right channel. I have been spending a lot of time trying to figure out what this noise can be so I have a lot of information about the noise. The best way to describe it is that it sounds like when you have a dirty volume control and every time you adjust it you get a loud crackling sound. I have timed the noise and it takes anywhere from 9 to 12 minutes for it to start from the time the amp is turned on. It continues until the amp is turned off. I have kept it on for 25 minutes to see if it would stop but it didn't. This noise happens without any input to the amplifier. The volume control on my preamp has no effect on the noise, the noise remains constant even at high volume. Once the noise has begun it happens intermittently with no set pattern but, there are no breaks in the noise except for the ten seconds or so between noises. From the responses so far looks like I had better get some new tubes.
You may have a cold solder joint on the tube socket.

You might also try some fine grit sand paper and clean the tube pins.
I'm not sure how the Golden Tube is set up, but Najo is right, this sounds like it could be the small signal tubes, rather than the output tubes (the larger ones). Try turning off the unit and swapping the small signal tubes between channels (if there is a way to do this). If the noise switches channels, you have probably found your culprit. If not, turn off the unit again and swap the output tubes between channels, see if that does anything. If after swapping all tubes from one channel to another the noise doesn't move to the other channel, you probably have a problem inside the unit, and should contact the manufacturer. Good luck.
I had a similar problem last week.I have a tube pre and SS amp.I was getting (L) channel noise just like you described.I put the (L) channel line-stage tubes in the (R) side and (R) channel tubes in the (L) no more noise.Sometimes just re-seating the tubes and/or cleaning the pins is all it takes.
Thank you so much for all of the ideas. I switched the driver stage tubes and the noise magically went away. This is great! the amp sounds great and I spent the rest of the night listening to it. This is a really great site, especially for a newcomer (to this site and to tube/analog audio). I have posted several times with problems and each time was given good advice from alot of people. At first I was hesitant to post but I'm glad I did. Again I want to thank everyone for your response and suggestions.
Rick Zerambo (Reading, PA)
One of the best things about the se40 was that it used cheap tubes. The sovtek 5881's can still be had for about 10 bucks each. The driver tubes are the ones where it got a little more expensive but there were only two per amp. I would switch all the tubes from one amp to the other. If the noise goes to the other amp then replace all the tubes in that amp.