FYI: If a tube looks like this, it's bad.

[tonymcbony]

White at the top the tube=vacuum has gone out of the tube.
The getter has oxidised.

I only mention it because it took me quite a while to figure out what the hell had gone wrong with my SVT.

[Arjank]

Originally Posted by tonymcbony

White at the top the tube=vacuum has gone out of the tube.
The getter has oxidised.

I only mention it because it took me quite a while to figure out what the hell had gone wrong with my SVT.

Valuable info for the FAQ

[Sliderbass]

...you could call that the "magic smoke" for tubes?

[Droot]

I once had a electronics professor who claimed all components were filled with smoke. If the smoke managed to escape, the part was junk. So far he has been correct 100% of the time.

[mpdd]

nice picture, it actually looks like it's about to rain in the tube, kind of like the snow globe at the beginning of citizen kane

[Arjank]

Originally Posted by Droot

I once had a electronics professor who claimed all components were filled with smoke. If the smoke managed to escape, the part was junk. So far he has been correct 100% of the time.

Thats one of the best conclusions for electronics components ever!

[Sliderbass]

...Of repairing and testing all kinds of communications gear, once the smoke is allowed to escape, its gone forever! All you can do is buy new smoke.

[My name is Mudd]

OK, so what happened to that tube?

[svtb15]

Looks like it leaked.... there is air in that baby... no good.

[BassmanPaul]

Yes the tube has lost its vacuum. The white stuff is what remains of the getter, normally silvery in appearance, that has reacted with the gasses and has lost its usefulness.

[Alex1984]

Yeah, vacuum tubes are no good if they're no longer vacuums.

[AwkwardLoudness]

Originally Posted by My name is Mudd

OK, so what happened to that tube?

The vacuum seal was breached and air entered the tube. The white stuff is metal oxides.

Loss of vacuum is only one failure mode for vacuum tubes. Tubes that look fine may be bad for other reasons.

[96tbird]

There are people on fleabay selling used tubes that look almost that bad for crazy prices. And that one is certainly finished. However, getters will, over time, slowly start oxidizing over the valve's life which is normal, as the plates and filaments continue to shed gasses. It will never stop. Just replaced the original 7027A's in my '74 V4-B and there is some oxidization but they work fine and have life in them as backups.

[okcrum]

Here's another:



Amp was dropped, cracked tube, air leak.

[seamonkey]

What's going on with the little tube? Is that tube shrinkage? Scared turtle thing?

[AltGrendel]

Is the getter the disks at the very top in the last pic?

Edit:

Never mind.

Getter

[okcrum]

Originally Posted by seamonkey

What's going on with the little tube? Is that tube shrinkage? Scared turtle thing?

That one had an H-K short.

[Ken R]

Old British bikes had the same problems.

Originally Posted by Droot

I once had a electronics professor who claimed all components were filled with smoke. If the smoke managed to escape, the part was junk. So far he has been correct 100% of the time.

[96tbird]

^ ROFLAO Ken R, have you posted that in the "post a funnier picture than the last post" thread? WIN!!

[okcrum]

Originally Posted by Ken R

Old British bikes had the same problems.

Yes, Lucas, Prince of Darkness.