Power Tube Replacement

[jacotosh]

Just wanted some input from all you vintage tube amp lovers out there. When and how often do you replace your power tubes? (I know this depends on usage) How can you tell if a power tube is in need of replacing?

I have a late 70's V4B with the orginal tubes in it. I was thinking of taking it to a tech to give it a check up, and make sure everything was working properly. So, I was thinking of having the power tubes replaced and rebiased at this time. Should I keep the orginal tubes in there as long as possible to preserve the "vintage tone" or would replacing them give me a more optimal sounding amp? Also, any prefrence on the Sovetek or JJ Tesla 7027s?

 

[MIJ-VI]

How does your amp sound right now?

 

[jastacey]

The thing about tube amps ... is .... the time to change out tubes is really subjective, some folks will tell you after a certain amount of time ........ some will tell you change them when the output/sound diminishes ...my experiance is the 7027's last a long time and what happened in mine was the drive and inverter tube went out of spec ( 12au7 & 12dw7 ) ...when I did put my amp in the shop I elected to change out the power tubes ( they had the Sovtek 7027 in stock ) and with that combination of tube change out, the amp really came back to life ...the only other tube change I'd recommend is the 6K11, that tube really doesn't wear out ...but when I did change it out, I noticed that the tone really tightened up ...this tube is one of those, that ...if you own a v-4, you should always have a spare one, the only other issue on these amps is the caps in the power supply are about 30 some years old and a word from some one who has had this type of amp. start saving for a cap job ....don't want to scare you in saying that you need to get it done ....but be aware that once it starts buzzing/motorboarting ...it's time to fix that issue ..... some folks are running JJ's 6l6GC and have reported great results, so it all boils down to $$$$ and what you have access to ...IMHO

 

[NecroticImbecil]

I change them when something isn't right. Sound is off, glowing unevenly, noisier than usual. When this happens I'll also try changing preamp tubes, changing them out one at a time. If changing preamp tubes doesn't do it, I'll change all the power tubes. 5 years so far, but I've seen amps that were fine with the original 40+ year old tubes.

That's what I do. The "proper" answer is probably to have amp checked out periodically and rebiased as needed, even when the power tubes are still good. If you knwo you can trust your tech not to just make you buy a new set of tubes from him because he wants the money. Of course it is also best to have the amp biased whenever you have the power tubes changed as well. I don't usually bother unless hte amp doesn't sound right with the new tubes, but that's me and I do things wrong all the time.