Blown Power Tube, Dammit!

Early B.

So I was sittin' in my sitting position while listening to some tunes. After about three minutes into it, one of my power tubes starts glowing more than usual. "Uh-oh," I say to myself, as I reach for the off button. Too late, 'cause she blew before I had a chance to react. The fuse went, too.

I should have seen it coming. Two days ago there was a little bit of snap, crackle and pop coming out of my right speaker for a couple of seconds, but I dismissed it as a warmup belch. I ordered a pair of them so I could at least have one spare handy in case (ugh, when) this happens again.

I will admit, however, that the build quality of my Chinese Shuguang KT88's ain't the greatest. But damn, they sound so sweet!

Is there anything the user can do to minimize these occurences? Or can I expect to get a bad tube every now and then?

halo

TAD recommends changing the poewer tubes every 18 months:

"Output tubes last 1 to 3 years in most tube amps. Not a bad idea simply replacing output tubes every 18 months to avoid an ugly end. Bad tubes (shorted) will blow the easy to change external power fuse. Keep 18-month replaced (used) tubes for spares in case you have one in the future blowout before 18-months has passed. Tubes are 100% hand made. Hand micro-welded inside, hand-blown glass outside. Human factors make them delicate from the start. Off the assembly line 50% do not function. The remaining 50% have ½ test out of usable range. 1 in 4 made are shipped out."

"Even with extensive testing there is a 2% chance you will find a tube that quits prematurely. Handle your tubes carefully. Always set the bias immediately when changing tubes. External test points allow you to easily observe how your tubes are doing. A very high or very low bias reading (off by >30%) on one tube with others looking identical indicates the odd tube has a problem and needs replacement. A simple regular 6-month bias check and complete output tube replacement every 18 months will generally provide non-stop entertainment."

audiobliss

Wow. Not very favorable odds for the manufacturers, eh? That's amazing.

RuSsMaN

Buy better tubes/

Early B.

RuSsMaN wrote:

Buy better tubes/

Well, the Shuguangs replaced EH tubes; the EH's visually appear to be built better. Had an EH blow out on me. Before the EH's I had Svetlana 6550's -- also well built, I think. One of them blew out as well and one was DOA. Neither the EH's or the Svets come close to the silky SQ of the Shuguangs, IMO.

halo

EarlyB - what kind of time frame are you talking about here? Does the Jolida accept KT-77's? Maybe RuSs meant NOS tubes?

jm1

Early B. wrote:

Is there anything the user can do to minimize these occurences? Or can I expect to get a bad tube every now and then?

You can always upgrade to a good SS amp.

RuSsMaN

What amp do you have these in, and what sort of biasing setup does it have? If it's doing it fairly consistently, its not a tube problem, its an amp problem.

halo

jm1 wrote:

You can always upgrade to a good SS amp.

Blasphemer!

Early B.

RuSsMaN wrote:

What amp do you have these in, and what sort of biasing setup does it have? If it's doing it fairly consistently, its not a tube problem, its an amp problem.

It's a Jolida 502 int. amp. Manual bias. These tube blow ups have occurred over a 2 year period.

I suppose I could check the bias more often -- perhaps on a monthly basis.

Early B.

jm1 wrote:

You can always upgrade to a good SS amp.

Bend over so I can kick you square in the crack of your **** for that statement.

faster100

Bias can have a impact.. however you know what's up with good gear and i doubt its the bias causing THAT many blown tubes.. Id have it looked at before you buy Good tubes and it ruins a vintage tube or something.. I agree, its the amp.. most likely

maybe it was those blasted 12bz7's you tried? I'm rolling them in my amp this morning as we speak.

jm1

Early B. wrote:

Bend over so I can kick you square in the crack of your **** for that statement.

Should I line you up every time you tubies try to force tube based components on everyone? Personally, I wouldn’t want to see your crack, nor anyone else’s, under any circumstances.

I have yet to hear a tube based pre amp or power amp that I would consider purchasing, regardless of price. Instead of focusing on more watts, I focused on refinement and purchased a SS amp with more neutral characteristics. Combined with a pre amp from the same manufacturer, this has proved to be an outstanding combination.

audiobliss

And so in spouting out about how you hate those who force tubes on everyone, you become no better than your enemy by parading the SS flag.

He's obviously not dissatisfied with his amp; if he's into tubes, he's into tubes.

fredv

I bought a quad of JJ E34L from tubedepot a month ago. 2 of them produced similar light "pop" after 2 weeks of use in the Eico. That only happened in the warm up period. When I switched them to the TAD-1000's, the fuse was blown within 20 seconds after the tubes started getting full current, the blow was accompanied with a loud pop out of the speakers, and everyone in the room jumped!!!! Talking about quality, this is 50% failure!!!!!! IMHO, blown fuse is probably the best of all the possible bad's .....

halo

What are you using now Fred?

As for jm1 - to each his own bro. If you don't like tube gear whoopdeedo for you. Early obviously likes his stuff and wants it to work right. It's a subjective hobby and if everyone liked the same stuff it would be really boring.

organ

jm,
We don't force people into tubes. We can suggest gear but we're not the ones purchasing. The member has the right to buy any gear they want. In your post, you're the one telling him to dump the tubes and go SS. You hear about people getting into tubes all the time. How often do you hear someone go back to SS?:rolleyes: Early wants to keep the glow in his home and sand paper away from his ears;).

Early,
Sorry to hear your loss bro. Yes, from what I've read around the net, the Shuguang's seems to be the best sounding current production KT88 tube. Like Halo explained in great detail, some tubes will just die prematurely.

One way of getting your power tubes to last longer is to find out what plate voltage and bias current the amp is running the tubes. Some companies run them hard and as a result, you get a shortened lifespan. Easiest way is to lower your bias by 15-20%. I doubt you'll hear a difference in sound. This will make the tubes run a little cooler and increase service life.

The longest running power tube I've had was the EH EL34. Got about 2 years of daily use out of them before bias began to fluctuate constantly. Sometimes it was running 12+hrs/day.

madmax

If it glowed VERY brightly (which you didn't go into) then its seal allowed oxygen in. If that is the case it either wasn't built well or you didn't follow the "push straight in, pull straight out" rule or it was handled improperly somewhere along the line. Probably just a defect.

JM, I've heard SS amps which sound as good as tubes. They were considerably more expensive than the Jolida and other production amps though. (Sorry, Just had to throw in my two cents ).

madmax

halo

Are you referring to a tube flashing when you first turn the equipment on or just glowing bright all the time?

Early B.

Halo wrote:

Are you referring to a tube flashing when you first turn the equipment on or just glowing bright all the time?

No. The tube seemed fine when I first turned it on, then suddenly a bright yellow flame emerged in the back of the tube, then she blew within seconds...

fredv

Halo wrote:

What are you using now Fred?

The Sveltana's are back to the monoblocks as I only have 6 known to be good JJ E34L. I am not sure I should buy another quad, pair, or not at all. For the sake of exploration, I did put those JJ's in the Eico's again. Besides the few light pops at the beginning during warm up, nothing bad happened. My conclusion is that the TAD's might drive the tubes harder than the Eico. When I rebuilt my Eico, I indeed put in a higher value resistor in the auto bias circuit to lower the current for tube longevity. I really didn't hear much a different as Maurice said.

Early B.

OK, I'm up and running again. Got one more question --

Does it matter where your volume level is set on a tube integrated amp at the time you turn it on? In other words, is it harder on the tubes if the volume is set at your typical listening level upon powering on or is it best to always turn the volume down, power up, and let the tubes warm up before you turn the volume back up?

Thanks.

fredv

I think the tubes wear out faster when they are pushed before they are fully warm up. If the source is not feeding any input to the int, then there should be no load; hence, won't do any harm to the tubes. However, if the source is on and playing, the tube will be pushed while they are warming up. Other then this lame reason, I can't think of why the volume control could impact the tubes in this regard.

madmax

Early B. wrote:

OK, I'm up and running again. Got one more question --

Does it matter where your volume level is set on a tube integrated amp at the time you turn it on? In other words, is it harder on the tubes if the volume is set at your typical listening level upon powering on or is it best to always turn the volume down, power up, and let the tubes warm up before you turn the volume back up?

Thanks.

This is from experience. Always warm up the amp first. A few times I didn't and noticed a lot of blue color showing up in the tubes. It was flashing with the beat. I'm sure this is not a good thing. You can see it a little at high volumes even after warming up but mine did it violently when cold. I never did look up what blue color meant. Besides, higher volume will cause it to heat up quicker maybe causing physical problems with the tubes.
madmax

faster100

I read blue is normal or can be a bad tube if it glows almost purple.. I just noticed the other night my tubes are blue or purple so i hope all is well, its not a bad tube because i tried two of my new EH 6v6's and they did the same thing, hope the voltage to the tubes isnt to high..

fredv

faster100 wrote:

I read blue is normal or can be a bad tube if it glows almost purple.. I just noticed the other night my tubes are blue or purple so i hope all is well, its not a bad tube because i tried two of my new EH 6v6's and they did the same thing, hope the voltage to the tubes isnt to high..

Do you mean the filement or the blue/purple mark on the glass? All the JJ's and EH's that I have this blue/purple glow on the glass.

faster100

On the glass, so that is normal? Im so confused.. I was freaking out when i first seen it.. My 12ax7 driver tubes dont do it nor my 5u4 rectifier

madmax

Mine are always blueish too, just not flashing and not very bright like when I crank it up cold.
madmax

faster100

ah ok, yeah mine are a low lite blue/purple.. but even the vintage original 6v6's do it

organ

The blue glow is normal. It's excess electrons that didn't get attracted to the plate and shooting around in the bulb and hitting the glass. I think it makes the tubes super sexy.

Here's an explanation...
http://www.jacmusic.com/html/articles/blueglow/blueglow.htm