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Power Tube Failure

A little while ago a small tube (in my Phono-Preamp) died.  It was a subtle affair in which the tube turned white and the glass cracked, not necessarily in that order.  This failure was interesting, but not dangerous.

Yet, this event got me wondering - what happens when a power tube dies?

My Preamp's power tube runs quite hot, and I am concerned it may be a FIRE HAZARD when that tube fails. 

My second concern is that my Preamp may be DAMAGED when the power tube dies.

So, I am hoping to hear from anyone who has EXPERIENCED a power tube failure and can provide any insight regarding what to expect. 

 

notes:

a. Yes, my Preamp counts hours, but I own several power tubes and do not know how many hours of service each has provided. 

b. Testing these tubes is not plausible - I do not have a tube-tester, and there are no HiFi retailers within a reasonable driving distance.

Thanks in advance for your stories!

Best,

inagroove
elliottbnewcombjr
7,731 posts
 

I've found shorts, and weak tubes, once I put a 6sl7 in a 6sn7 socket (or reverse of that) and blew the tube, i.e. dark inside, dead.

I have never had the glass break. It is not how they die.

get thee an inexpensive tester, here's one

https://www.ebay.com/itm/377064722132?mkrid=711-53200-19255-0&campid=5338381866&toolid=10001&customid=2aedea5c-4626-11f1-8ae2-383333336661

always test for shorts first.

everybody's gonna say ..... I'm telling you, you are blind now, get a simple tester at the very least.

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audphile1's avatar
audphile1
7,882 posts
 

When I owned Rogue ST100 a power tube failed and with it took out several parts in that channel. I live only about an hour and a half away from rogue audio and dropped the amp off for repair. I sold it shortly after and never bought another tube amp. 
A properly designed top flight modern solid state component, be it the amp, preamp, phono stage or DAC, is no less musical than a tube component. Especially considering that modern tube gear doesn’t sound much like the classic tubes. SS is more consistent sonically, performs just as well, and imparts way less audiophile nervosa on its owner than tubes. Nothing to roll. Press the button and enjoy music. 

paradisecom
503 posts
 

You might not need a local HiFi retailer to test your tubes.  Many guitar amp repair shops have tube testers, as well.

ghdprentice's avatar
ghdprentice
9,429 posts
 

@jea48 

+1

If you change tubes at recommended times it is very unlikely they will "go out".

Tubes age out typically by hardening sound, or lower output. but occasionally will flash, even less commonly pop.

Very occasionally they will crack and blow... very uncommon, but it does happen. Far more likely with old tubes beyond their recommended usage. 

Under the latter circumstances it may take out the resistor next to the tube... placed there for that very reason to protect the rest of the amp. Seldom it it more than that. 

A friend of mine had a problem with a tube amp from Rogue within the warrantee period and they would not fix it because it was tube related... so I will not buy or recommend Rogue products. 

I have run tubes for a couple decades and never experienced a popped tube. It is uncommon but occasionally happens. 

If you think there may be a couple thousand hours on the tubes... I'd just change them out and reset the counter. Then you can be sure of getting the best sound and know where you stand. 

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