12AX7 failure

Why do you fret over nothing ? Valves 'GO'. It's their nature.

Graham

Passed that ages back sadly. Mind you I still get taken for being in my

Graham

I take it that went over your head?? :)

Not at all. :-)

Graham

Lost his towel??

The 12AX7 owner said he was a careful owner, but maybe not careful enough. Maybe if he had ordered the Snake-Oil brand tube cozies......and vibration smugglers and wrapped his 12AX7's in those that tube would be alive and transfering the emotion of true music today..........

ing

e.graffiti.net/diverse-

Hmmm... you did not differentiate whether the tube is 4-years-in-use NOS, or 4 years from manufacture. Nor did you specify country-of- origin if New.

If this is a Chinese 12AX7 four years from manufacture - that is a VERY long time for some of these tubes. The owner should count himself lucky for even that much life.

Peter Wieck Melrose Park, PA

roing

rid

I have some Groove Tubes here and they are all "Made in China". They are marketed to the Guitar amp user. Many are sold through Sam Ashe, Guitar Center and other music shops. Even the box they come in is styled like a Fender amp. They have an odd distortion marking scheme and biasing advice. The tubes are rated as to distortion: Early Distortion 1-3, Normal Distortion 4-7, and Latest Distortion 8-10. " The bias should always be adjusted when changing power tubes, UNLESS YOU ARE REPLACING GROOVE TUBES OF THE SAME TYPE AND RAITING, THEN NO ADJUSTMENT IS NEEDED. " Bad advice IMHO.

Find an old timer repair guy and they will tell you that getting only

Randy AB9GO

p.s. Here is an example of running forever:

Age: 107 years and counting (as of 2008) Installed: First installed at the fire department hose cart house on L Street in 1901. Shortly after it moved to the main firehouse on Second. In 1903 it was moved to the new Station 1 on First and McLeod, and survived the renovation of the Firehouse in 1937, when it was off for about a week. Proof of Longevity: From local newspaper records; also GE engineers researched it. Was donated to the Fire Department in 1901 by Dennis Bernal who owned the Livermore Power and Light Co.

And there is another one in Texas:

Happy 100th B-Day Palace Bulb!!!

On September 21, 2008 the Palace Bulb of Fort Worth, Texas will be the

Do their brains suffer from tin pest ?

Graham

arly

ing

That's funny! I buy all of the old 60/40 solder I can find because if the tin dendrite issue that will be comming in the future. Tin dendrites have been known to grown to over 10mm in length. That is why NASA and critical biomed devices (pacemakers and ICD's etc) will continue to use lead in their solder, and so will I for as long as I have a supply.

Randy AB9GO

Current carrying capacity of dendrites Bjorndahl, W.D.; Lau, J.C. Aerospace Applications Conference, 1994. Proceedings., 1994 IEEE Volume , Issue , 5-12 Feb 1994 Page(s):399 - 405 Digital Object Identifier 10.1109/AERO.1994.291179 Summary:Dendrites are sometimes found on electronic hardware during failure analysis or trouble shooting activities. Problems due to dendrite formation can vary from catastrophic failure to occasional electronic glitches. If a dendrite is thought of as a fuse in a circuit, then it is apparent that it can have, depending on size, a wide range of current carrying capability. Mathematical modeling and experimental analyses were conducted to determine the reasons for the wide range of observed behavior. Mathematical modeling indicates that the resistivity of the dendrite and the thermophysical characteristics of the substrate on which it is grown determine its current carrying capacity. More specifically, the modeling indicates that maximum dendrite size and time to failure are determined by the power loss within the dendrite and the rate at which heat can be transferred away from the dendrite. Small dendrites are stable and can grow until they reach a size at which internal heat generation cannot be accommodated by the heat loss due to conduction through the substrate. Dendrites in low voltage applications on substrates with high thermal diffusivity are more likely to lead to failures with high power loss, whereas dendrites in high voltage applications on low thermal diffusivity substrates (e.g. tin on glass/epoxy circuit board material) are more likely to lead to high resistance shorts. Experimental results and failure analysis observations agree qualitatively and semi- quantitatively with the results of the idealized dendrite model

?

Likewise.

You can still get it legally even in the EU for repair of pre PB-free equipment.

Do you have a link for that ? I heard somewhere a typical tin whisker can support 30mA.

Graham

Depending upon their use, they may go quickly or slowly.

Regards, H.

ing

e.graffiti.net/diverse-

Hi,

Given that it is dead, if you really wish to find out you could always crack & remove the glass and then check the internal connections. Nothing to lose!

ipment.

Yes, but the price is getting higher and it is no longer commonly stocked.

support 30mA.

ieeexplore.ieee.org/iel2/1110/7210/00291179.pdf

Is where I got the abstract. I am not a member so I cannot access the entire document. Sorry.

Randy AB9GO

Yes, but the price is getting higher and it is no longer commonly stocked.

I have at least 4 or 5 rolls of 63/37 or close to that.. enough to last me personally for the rest of my life. Maybe I could send some out in 30' chunks for those that need it?

equipment.

Farnell.

Graham

support 30mA.

Likewise.

Graham

For some reason, whenever a thread starts with "12AX7", "EL84", or "6L6", I feel like I'm viewing the famous "Three Stooges" skit, "Niagara Falls", after I read all the replies!

Why is it so important to debunk a failing tube that gave four years of satisfactory performance?

Dude, just $#!^can the offending tube, and move on!

Omer