Is changing tubes something to worry about

[Gmountain]

I was reading on another forum about a kid who got killed taking apart a microwave oven and a capacitor discharged and killed him.

Do I need to be aware of anything when changing tubes on an amp? Is there something that could hurt me. Of course, the amp would be unplugged.

[Song]

I do not know because I've always had a tech do it. Hope this helps:
https://www.bing.com/videos/search?q...mp&FORM=HDRSC3

[M Hayden]

Don't change them when they're hot; you'll definitely burn your fingers and possibly damage the tubes. Don't ask how I learned that....

Most tune amps won't discharge the caps on you while you're swapping tubes, and you'd have to grab the connectors at the bottom to get shocked, anyhow.

Be gentle, do it when the tunes are cool, and use a gentle circular motion and they'll pop right out and install easily.

[ghostnote]

Yeah, it's not really a problem - just don't stick your fingers into all those wires and electronic parts and you'll be fine. Grab only the tube. I've been changing 'em for decades and I've never had an issue.

[Bob Womack]

Also, if they have a plastic base, only pull on the base. The glass envelope is only glued to the plastic bass and the heat eventually cooks the glue so it crystallizes and turns to powder.

Of course, if we are talking about a modern design with two tubes set in an A-B configuration, you have to think about biasing the tubes as well.

Bob

[clintj]

In addition to the above, replace them one at a time with the new ones or take other steps to make sure the right tube is in the right spot. I had an amp in for repair where the owner pulled all the tubes at once, put in the new ones, and got a 12AX7 preamp tube and an EL84 power tube swapped. Smoke and fury for about 5 seconds, then the fuse blew. Thankfully, the fuse limited damage to a couple of resistors.

If your amp has a bias adjustment, you may want a tech's help to set it for you for best operation. Setting bias and power tube idle does involve taking measurements on high voltage.

Sent from my SM-G920V using Tapatalk

[Big Band Guitar]

Originally Posted by Bob Womack

Also, if they have a plastic base, only pull on the base. The glass envelope is only glued to the plastic bass and the heat eventually cooks the glue so it crystallizes and turns to powder.

Of course, if we are talking about a modern design with two tubes set in an A-B configuration, you have to think about biasing the tubes as well.

Bob

I have been servicing electronic equipment for 39 years. Everything from tube type power amps to electron microscopes.

When changing tubes of the same type Biasing is not needed unless there are bigger problems like burnt components but you would be able to smell that and see the smoke.

[Bob Womack]

Originally Posted by Big Band Guitar

I have been servicing electronic equipment for 39 years. Everything from tube type power amps to electron microscopes.

When changing tubes of the same type Biasing is not needed unless there are bigger problems like burnt components but you would be able to smell that and see the smoke.

However, changing power tubes from brand to brand and era to era is another matter. The idle voltage can be so different that you can end up wasting tube life if you don't get it set.

Bob

[blue]

Originally Posted by Bob Womack

However, changing power tubes from brand to brand and era to era is another matter. The idle voltage can be so different that you can end up wasting tube life if you don't get it set.

Bob

Yup. Don't technically "have to" but it's a good idea. The more efficiently things operate, the longer you can go without servicing the amp.

[redir]

I've always been told to wear gloves or at least wash your hands really good when handling tubes. Old wives tale? I don't know.

But yes you can get seriously zapped by a tube amp, don't ask me how I know.

[muscmp]

if i'm changing output tubes and the amp is able to be biased, i do so. i either buy matched sets, or, if they are tubes i presently have, i match the best i can with my tube tester.

i've never washed my hands, nor wore gloves, when changing tubes. however, if i just finished a greasy burger, i'm going to wash prior to doing anything else anyway.

play music!

[blue]

Originally Posted by muscmp

i've never washed my hands, nor wore gloves, when changing tubes. however, if i just finished a greasy burger, i'm going to wash prior to doing anything else anyway.

play music!

Just like those old halogen tube lights. Oil on a hot surface cooks, and becomes a hot spot.

[M Hayden]

Originally Posted by Bob Womack

Also, if they have a plastic base, only pull on the base. The glass envelope is only glued to the plastic bass and the heat eventually cooks the glue so it crystallizes and turns to powder.

Of course, if we are talking about a modern design with two tubes set in an A-B configuration, you have to think about biasing the tubes as well.

Bob

Unless they're cathode-biased, but that isn't very common these days.

[Mr. Jelly]

Back in the day I used to change tubes all the time. I'd find tubes in junk shops and in old radios etc. I'd change them out to see how the different tubes sounded. Then they started making tubes again and even boutique tubes.

[blue]

Originally Posted by Mr. Jelly

Back in the day I used to change tubes all the time. I'd find tubes in junk shops and in old radios etc. I'd change them out to see how the different tubes sounded. Then they started making tubes again and even boutique tubes.

Heck, just back in the late 90's there was doom and gloom about "no more tubes. Only crappy Russian and Chinese ones, and we'll run out of those in a few years..."