Tube sparking/flashing during warm up

[Rob N]

What possible causes for a good testing tube to do this? Internal short?

I've had it happen with an EZ80 rectifier and a 5687 triode

[n_maher]

Not sure why it'd happen with an input or output tube but it's not all that uncommon with rectifiers, especially if you're running them near the max plate current. The Menace has been known to have a little lightning show in its rectifiers at startup.

[aardvark baguette]

OT, but do tubes and/or transformers usually make a very quiet pop when being turned on? My EAR always makes a very very faint clicking noise. I figure its normal, but I know didly squat about tubes or transformers.

Its very quiet. No sparks, just an audible click, about .5 seconds after turning on the amp.

[n_maher]

Tubes can certainly make noises as the metal inside expands as it heats. I have one set of tubes (outputs) that take a good 30 minutes to heat up to operating temperature and stop making noise.

[Rob N]

I believe this is due to faulty tubes.The sparking/flashing from within the tube was significant and should not happened to a 5687 triode.The first time I switched on I just got the normal heater glow, no fireworks.

The only time I've had problems with tube gear was when I connected the two power cords to my SDS-XLR amp unit from the power supply round the wrong way.I got lightning across the rectifier and after switch off all the LED's remained on for sometime as they were receiving capacitor discharge.I spoke to Mikhail who said no damage would have been done and sure enough when I connected the umbilicals the correct way round everything was fine

[n_maher]

I can't believe that he made the amp so that it's possible to connect the power cords that way. With the Menace, although it uses the same connectors for all of the power connections, it's impossible to hook it up wrong due to the sex of the connections used at each end. It wasn't hard to do and was a definite design consideration along with making sure that the HV was never exposed on male pins to limit the chances of cooking myself.

[Rob N]

I agree it should have been made so that wrong connections were impossible

[Dusty Chalk]

KG would know for sure, but I thought it was because of leftover air inside the tubes, no? Arcs are either because components are too close for the voltage they are trying to displace, or because there's still a conductor (I.E. air). I vote for the latter, since the tube tests normal. It will affect the life of the tube (I.E. shorter), but should work fine for now.

Someone confirm or deny, this is "thinking out loud" stuff -- which I liken to chewing with one's mouth open.

[Fitz]

That also brings up the question of whether the tube tester tests at the same voltage as the tube is being used at.

[hirsch]

Egon Spengler, Peter Venkman and Ray Stantz expound on ES1 umbilicals:

Dr. Egon Spengler: There's something very important I forgot to tell you.

Dr. Peter Venkman: What?

Dr. Egon Spengler: Don't cross the streams.

Dr. Peter Venkman: Why?

Dr. Egon Spengler: It would be bad.

Dr. Peter Venkman: I'm fuzzy on the whole good/bad thing. What do you mean, "bad"?

Dr. Egon Spengler: Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.

Dr Ray Stantz: Total protonic reversal.

Dr. Peter Venkman: Right. That's bad. Okay. All right. Important safety tip. Thanks, Egon.

[n_maher]

That also brings up the question of whether the tube tester tests at the same voltage as the tube is being used at.

It's my understanding that it's highly unlikely that a tube tester is testing the tubes at the same voltage levels experienced while the tube is in use.

[luvdunhill]

It's my understanding that it's highly unlikely that a tube tester is testing the tubes at the same voltage levels experienced while the tube is in use.

well, depending on how linear the tube is, this may not be an issue... just like matching BJT hfe using a DMM might be an issue.

I know some tube vendors that will honor this request.

[n_maher]

I know some tube vendors that will honor this request.

It's funny you'd say that, I've had more than one tube vendor tell me not to bother matching tubes because of the inherent non-linear behavior and the fact that they would be matching them at vastly different operating points compared to my application.

[luvdunhill]

It's funny you'd say that, I've had more than one tube vendor tell me not to bother matching tubes because of the inherent non-linear behavior and the fact that they would be matching them at vastly different operating points compared to my application.

Perhaps for a plate loading resistor design, what what about a proper CCS loaded tube, which will behave much more linearly?

[n_maher]

I'm sure there are examples of when it's worth paying for and worthwhile in general but I think the basic idea is that unless the vendor is working closely with the buyer and the buyer is also knowledgeable that more often than not it's wasted $$.

[luvdunhill]

I'm sure there are examples of when it's worth paying for and worthwhile in general but I think the basic idea is that unless the vendor is working closely with the buyer and the buyer is also knowledgeable that more often than not it's wasted $$.

I think it's worthwhile, because it marginally ensures that the tube has actually been stuck in a tester

[n_maher]

I think it's worthwhile, because it marginally ensures that the tube has actually been stuck in a tester

All the vendors that I use double test their tubes before shipment and offer some meaningful DOA warranty. Of course, I also test all my own tubes prior to use as well.

[kevin gilmore]

KG would know for sure, but I thought it was because of leftover air inside the tubes, no?

NO. If the getter is still silver colored, then the vacuum is at least 1 x 10**-8 torr.

This does not mean that there isn't crap in the tube. excess cathode material can

get in between grids and such and that stuff is certainly conductive. Furthermore,

even in a perfect vacuum (there is no such thing) there is a minimum distance at

which 2 conductors will arc depending on the voltage between them. Lookup

Paschens law. In fact some noble gas in the tube is a good thing.

Most of you probably don't know that for at least the last 10 years, all incandesent

light bulbs, no longer have a vacuum in them, but rather are filled with argon gas.

Much faster to make lightbulbs that way.

There are exceptions, but most consumer tube testers don't test at more than 250

volts with the exception of tube cap rectifiers.

[Dusty Chalk]

NO. If the getter is still silver colored, then the vacuum is at least 1 x 10**-8 torr.

This does not mean that there isn't crap in the tube. excess cathode material can

get in between grids and such and that stuff is certainly conductive. Furthermore,

even in a perfect vacuum (there is no such thing) there is a minimum distance at

which 2 conductors will arc depending on the voltage between them. Lookup

Paschens law. In fact some noble gas in the tube is a good thing.

Well, I did say the other choice was that some components could be too close together for the voltage, but then it wouldn't test 'good', would it?

[n_maher]

but then it wouldn't test 'good', would it?

It would if the test voltage was significantly lower than the operating voltage.