[DenverEd]

My Twin blew its fuse the other day. I replaced the fuse and it would blow again the second I turned it on. So....off to the amp repair guy. He found a fried diode on the power supply - apparently no big deal to fix. However, he said that my output tubes needed replacing. What do I know, so I said go ahead ($50). Now I am wondering if this was really necessary. How often do y'all change your tubes?

[tigerstrat]

It depends on how much and how hard you use the amp. If you play about 1-2 x a week at moderate levels, you might go as long as 3 yrs before they need replacing output tubes. Preamp tubes last MUCH longer (20+ years) but apparently newer ones only last like 5-6 years (from what Ive picked up on some recent discussion boards). Your tech was probably not yanking you (unless he blew off the bias check & adjustment... as some do)

[DenverEd]

Thanks for the info. I probably go 30-40 hours a month and have used this amp on and off for about 4 years. The amp guy did say you have to adjust the bias everytime the tubes are changed, so I guess all in all minimal yankage.

[DenverEd]

New problem. I turn the power on and wait a couple of minutes. Then I hit the standby switch. After 4-5 minutes I get a large popping sound (even if the volume is turned way down). After that, everything seems fine. I took it back to the amp tech and he replaced one of the smaller tubes and said this should do it. He thought that the tube was going bad and as it was heating up it would pop. He banged on all the small tubes and could kind of replicate the popping sound on the one tube he replaced Well, that didn't fix the problem. I Still get the pop at 4-5 minutes. Any ideas? A different tube is bad? Any risk in causing more damage if I continue to use it in its current condition? I am going to bring it back next week, but really need it over the weekend.