Time to change tubes?

[mesamaster]

I get a horrible squealing feedback through my triaxis. I bought it a couple weeks ago with a 2:90.

The guy i bought it from said he has had it for 4 years and never changed the tubes, be he said he never played it much.

what should I do? does it need to be retubed? what tubes should i use if necessary? i do like high gain, but i dont like muddy sounds either

help!

[eviltwin]

microphonic feedback on one of the tubes?

I don't know much about the 2:90, but if it's true stereo you may be able to troubleshoot it channel by channel. I sugges you start with the 12AX7 tubes (I'm guessing the 2:90 uses a couple of those or similar) before you look at the power tubes (6L6 ?), those can also fail, but are less likely to go microphonic.

[mesamaster]

I think the preamp tubes are the ones I am more concerned about. I dont know how likely they need to be changed, it has been at LEAST four years since they were changed.

[fleeeep]

strictly speaking, pre-amps shouldn't need to be changed periodically, only if one goes bad, they can last for many years.
try changing the power tubes first as these wear out between 6 months and a year depending on use.
if that doesn'y solve the problem then bring the pre-amp to a tech and have him find if one of the pre-amp valves has gone bad