6080 tube goes bad while in storage? [resolved]

[bluelair]

Hi, I built the Crack around 4 years ago, had it working fine with the included tubes. It sat stored, powered down, in a climate controlled room for about 3 years. Recently powered it up again and was getting a lot of noise and that "farting" clipping sound volume was pushed.

Cleaned tube pins and used DeOxIt on the tube sockets....got a little better.  So I tried a NOS 6080 and a new Sino 6AS7G from Tube Depot.

The new 6080 sounded better than the first, but still had a good bit of noise.  So I tried the 6AS7G and that sounds wonderful. Getting a small bit of hum but sounds great.

So my question is:  The original 6080, could it have gone bad from sitting, and the 2nd 6080, that should work, right? Making me think I need to go over the circuits again.....Any suggestions?

[Doc B.]

Not enough info. You need to measure voltages with each of those tubes installed and compare. You could also put in the older tubes and let them cook for a while. This might "wake up" the heater and improve the emission, and it might also activate the getter and remove any gas that might have leaked into the tube. Or the tubes just might be on their way out.

[Paul Birkeland]

was getting a lot of noise and that "farting" clipping sound volume was pushed.

It's entirely possible that this is all down to a solder joint that was a little iffy 4 years ago, but from sitting in storage it has oxidized enough to be a problem.  The farting sound you describe would lead me to look for a flaky joint.  Swapping tubes will move things around under the chassis as you plug and unplug tubes, so it's not necessarily a good idea to draw conclusions about good tube/bad tube from just that information.

Most of the 6080s we provide have been sitting around for 50 or 60 years already, 4 more years isn't going to do anything.

[bluelair]

Great advice!  I reflowed the solder joints, especially around the tube sockets.  Some of the joints were a little lean light on solder so I followed the last few pages of the assembly manual, then took it through the resistance and voltage tests, everything checked out and I re-inserted the original 6080 and all is perfect again!  Thanks!