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Has Anyone Here Thought Of The Possible Fire Potential Of Tube Amplifiers?

KT 120's need a lot of room to breathe ... mostly why I went with a custom chassis on my dynaco clone ... these temps are significantly lower than what you see on the stock chassis after about a half hour idling ... (ambient temp was around 68F when I did the readings.)

tube-temps.jpg


Biggest difference I'd think is the venting around the tubes ... Open chassis underneath, and the heating of the glass pulls cool air up from underneath for a real decent chimney effect.
 
The Bogens have vent holes already, which is handy. Its a fairly smallish chassis though, not much I can do about spacing on these. The tubes are about 3/8" apart and one is less than 1 inch from the power transformer. I did consider rebuilding them on a new chassis as a genuine twin mono design, but when I stacked the two together and tried to pick it up I decided against that. They weigh around 30 lbs each.
 
I damn near had a fire a few days ago with kt88's based amp. It had a pair of cheap Chinese tubes in it without the center cap to keep someone from doing what I did. The kt88 wasn't installed correctly and it was quite a show. It light up a bright green and the magic smoke poured out of the amp along with a loud hum. What's even stranger is the amp seems to have suffered no ill effects.
 
Had an Audio Research D-60 amp blow a cap way back in '92 and burn a ~3" diameter spot on the top of our nice living-room wood entertainment center (which we still use). No more Audio Research amps for me (too much work to refinish the burned place ;)).

As far as installing an octal tube incorrectly, apparently it can be done. John Atkinson, editor/tester of gear that is reviewed in Stereophile, installed an EL34 incorrectly in the Jadis integrated he just tested. I also wondered how he could have been so ham-fisted (but, never say never - I might be next).
 
Yikes, that's a big hole!

And you're right- Never say never. Sometimes I surprise myself with the foolishness!
 
Sometimes a picture worth a thousand words... this is what happened to a (factory built and unmodified ) VELLEMAN K4040 amplifier. Fortunately the owner was present when " big flames were coming out from under the chassis" and had just enough time to rush to throw the amp out of the room before the fire could extend to the furniture and surrounding parts. Needless to say, the amp was damaged beyond repair and the only salvageable parts were the fuses who remained intact ! Obviously, VELLEMAN engineers never heard about safety (aka "flame proof") resistors and were not too concerned about safety and potential fire issues.


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Fundercj said:
How do you install an octal valve incorrectly?
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Pretty easy to do when there's no notched center pin. That tube will fit snugly in any of the wrong positions just like it belongs that way. I'd also bet a week's pay that I'm not the first one to do this. It took me a good pair of glasses, light, and some patience to get it in there correctly20151129_125652_HDR.jpg
 
BTDT with the busted key. Sometimes nothing happens, other times interesting things happen. I bought a pack of those key repair things to keep me from doing that again. I've had them for a while now, haven't needed a single one. Best insurance against breaking a locating tab I've ever seen.

RE that Velleman, I've heard stories about those things catching fire before because of questionable design. Those pics are scary. Quite honestly, HV on printed circuit boards makes me a bit nervous anyway.
 
If I have a good tube with a busted center pin, I make a little sharpie mark in line with the keyway on the outside of the base. Makes it much easier to line up with the keyway on the socket.
 
I take the pin from a bad tube (with a dremmel) and epoxy it onto the good tube with the broken pin. Works like a charm.

One other thing I'd like to add to this discussion. I keep small fire extinguishers in the house - w/one next to each of my gear setups. It's cheap insurance.
 
x3workshop said:
I take the pin from a bad tube (with a dremmel) and epoxy it onto the good tube with the broken pin. Works like a charm.

One other thing I'd like to add to this discussion. I keep small fire extinguishers in the house - w/one next to each of my gear setups. It's cheap insurance.
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I don't know if they're still available, but overlay bases with new center pins that could be glued to a tube base used to be available.
 
x3workshop said:
I take the pin from a bad tube (with a dremmel) and epoxy it onto the good tube with the broken pin. Works like a charm.

One other thing I'd like to add to this discussion. I keep small fire extinguishers in the house - w/one next to each of my gear setups. It's cheap insurance.
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I believe the missing center pin is a great excuse to buy some better tubes.
Good idea about the fire extinguishers. I also have several scattered about.......you never know when disaster could strike
 
Interesting, I've never had or seen a broken centre pin before. Something to watch out for...
 
Fundercj said:
Interesting, I've never had or seen a broken centre pin before. Something to watch out for...
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I've had a few very nice 6L6GC Blackplates and a couple Mullard EL34's that were perfect (except for the pins) come my way at very low prices.
 
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Sam Cogley said:
I don't know if they're still available, but overlay bases with new center pins that could be glued to a tube base used to be available.
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I find the space between pin 1 and pin 8 and scribe an index line down the base at that point, Sharpie line on metal base. Wasting a good tube for a broken bit of Bakelite seems wasteful.
 
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