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After some routine maintenance on my V4 where I had him also replace my power tubes, he returned the old quad of 7027s and told me one of them had a short. The set was old and tired, but hadn't failed--so thinking about it later, I'm confused. Shouldn't a short in a power tube cause a pretty significant failure?

Dude wasn't trying to sell me new tubes--I brought him the new ones and told him to replace before he had even looked at them

benjuro wrote:After some routine maintenance on my V4 where I had him also replace my power tubes, he returned the old quad of 7027s and told me one of them had a short. The set was old and tired, but hadn't failed--so thinking about it later, I'm confused. Shouldn't a short in a power tube cause a pretty significant failure?

Dude wasn't trying to sell me new tubes--I brought him the new ones and told him to replace before he had even looked at them

That kind of thing can happen if the tube is shaken when its up to operating temps, they are really fragile and doubly when HOT. I have tube amps that use multiple output tubes and the amp continues to working fine even if a tube dies. Just depends on the circuit. I even own amps where I can remove power tubes to lower the output volume.

well,

as i understand it,

if one has a short, you are changing the amount of current that other tubes in the section are drawing, which is bad in the long run.

12XU2A3X3 wrote:well,

as i understand it,

if one has a short, you are changing the amount of current that other tubes in the section are drawing, which is bad in the long run.

depends on the circuit.

here's the amp i'm talking about. it's a mono block, so this is one channel and its a fully balanced design. the power tubes v5-v8 are + and v9-v12 are - of signal i believe. or vice versa doesn't matter. also its an output transformerless design. its a 60 watt design, and uses 12 tubes. per monoblock. so it gets toasty in the summertime and i'll pull two power tubes from each +/- from both amps to run them at 30 watts. If one of the 4 driver tubes were to die....that's a different story. there's a cool video of the owner playing music through the amps, and he takes a piece of metal and shorts the outputs...nothing bad happens really great amps.

Atma-Sphere envy! (I've got some AES Six-Pac monos....)

Just had a power tube go down in my Carr Slant 6V - one 6V6 with a short to grid. Had intermittent hum and then blew the fuse. Fortunately no major components were damaged, so I got lucky.

If your power tubes are old or don't test well, might just be best to play it safe and get a new set.

Butch1970 wrote:Atma-Sphere envy! (I've got some AES Six-Pac monos....)
If your power tubes are old or don't test well, might just be best to play it safe and get a new set.

Good advice.

speaking of atma-sphere, I've finally upgraded from their mp-3 to the mp-1

Every Cary amp i've ever heard I completely fell in love with their midrange. Actually owned a Cary cdp, one of the 303 models, before they put a tube in the output stage. That cdp made voices so present in the room that there were so many of those fooled ya moments. But it emphasized the midrange on every recording and got old, i don't always listen to female/acoustic guitar albums. replaced it with an audio aero capitole mkII se that I'm still enjoying to this day. its a damn fine sounding player, with telefunken output tubes