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jpervin
03-07-2006, 08:04 PM
What exactly is tube "burn-in"?

If it's anything like speaker break-in, how long does it usually take for tubes to "burn in"?

Bloozman
03-07-2006, 08:24 PM
It depends on how much gasoline you soak them in:eek:

Just kidding...I had a set burn in about 3 hours playing time...They smelled awful, but it went away pretty quick

RussB
03-07-2006, 09:41 PM
The Good tube retailers will take power tubes, and run them (in specifically designed "rigs") for 12, 24, 48 hours. This will "weed out" any bad tubes, and help to stabilize the tubes. Then the tube's operating parameters are recorded, and the tubes are then matched.

Note that all power tubes do recieve this from the factory as well, but in some cases, it's not so refined...

jpervin
03-07-2006, 10:56 PM
It depends on how much gasoline you soak them in:eek:

Just kidding...I had a set burn in about 3 hours playing time...They smelled awful, but it went away pretty quick

You should do standup comedy, Bloozman. :D

So do you have to be playing the amp to burn the tubes in, or does the amp simply have to be in "running" mode for the burn-in to occur?

jpervin
03-07-2006, 10:59 PM
The Good tube retailers will take power tubes, and run them (in specifically designed "rigs") for 12, 24, 48 hours. This will "weed out" any bad tubes, and help to stabilize the tubes. Then the tube's operating parameters are recorded, and the tubes are then matched.

Note that all power tubes do recieve this from the factory as well, but in some cases, it's not so refined...

Good to know...

I just bought a matched set of TAD 6L6s from www.allenamps.com (http://www.allenamps.com) for my Bassman, and they sound a bit "cold" to my ears. The original set of TADs that were in the Bassman sounded much warmer before one of the tubes fried.

VintageJon
03-07-2006, 11:49 PM
When I retube and amp's output tubes I "burn-them-in" for 1 hour at Max Clean signal into a dummy load, then retest the bias parameters. Sometimes I find a failure or some shift out of match. Then we begin again...

When I'm shipping a pre-amp tube I'll run it at idle for 8 hours, playing through the amp on and off as time allow. This is done in a SF Champ sitting on the bench. Sometimes find one that goes noisey or miscrphonic.
Then we begin again...

-Jon

TheAmpNerd
03-08-2006, 02:10 PM
I burn in all my output tubes for about 8 - 12 hours in
a special amp I have for this. Pre amp tubes are along
for the ride also. Then I log the output tube readings.

For amps that come in for service that need tubes
I select the tubes for the amp and also match them in
the amp. Depending on the service done to the amp
they'll remain and be tested with the amp for 4 - 80 hours.

The ol' bathtub curve...I try to weed out component failures
prior to an amp being fielded. The extra time typically prevents
amps from ever coming back. But every now and again,
some will. Sometimes it is a failure, sometimes
you think you fixed the problem and that wasn't it.
Ah, the challenges of the intermittent.

On some amps that I restify, I take them to the field
for gig and/or supervised jam testing. Nothing like a few
sets under the ol' belt. : )

Anything that needs to be dialed in tone wise w/respect
to the artist happens after the 4-80 test.

NOTE: The Bathtub curve actually looks like a bathtub. Both
ends of the graph are high with the middle being low. Component
failures are typically greatest at or near installation (power up)
and at the end of a components useful life. During mid life, the failure rate
is very low.

Okay back to work for me.