Switching preamp tubes: Is this something that a moron like me can do?

ajb · #1 10-04-2006, 02:22 PM

I know absolutely nothing about amps or electronics (the inner workings, I mean). I just got some new preamp tubes for my DB750. Can I switch out the old tubes myself or should I get a tech to do it?

If I do it myself, do I need to wear gloves to avoid skin contact with the tubes or anything weird like that?

About the only thing I'm clear on is that the power should be off when I do this. Any and all information on preamp tube replacement would be greatly appreciated.

alexclaber · #2 10-04-2006, 02:38 PM

Yes.

Alex

ajb · #3 10-04-2006, 03:09 PM

Thanks Alex. Succinct and to the point. But a little more info would be appreciated, i.e., will it be obvious where the 12au7 driver tube goes versus the three 12ax7 tubes? Things of that nature.

MuzikMan · #4 10-04-2006, 03:09 PM

Yes, it is very easy and straightforward to do. Just unplug the unit, pop it open, dont poke around the inside with a screwdriver

, pop the old tubes out and push the new ones in. They only go in one way. The only thing you can screw up is putting the wrong tube type in. Just read what comes out and replace it with the same type.

Easy as pie!

Shindig · #5 10-04-2006, 03:10 PM

Dude, you can do it. It's not rocket science.
You have more than one tube to do, so swap only one at a time (remove old and insert new) before you move to the next so you don't put the wrong tube in the wrong socket.
Be careful (gentle) when you remove the old tube (usually pulls straight up and out) and watch the pin alignment when you inset the new tube (you should see where there's a pin missing). In a nutshell - if you have to force it, it's probably wrong.
Be careful as the pins are easy to bend or break.
Some wear gloves and some don't, but they aren't needed.
Call Aguilar if you get stuck.
Good luck.

Hawkeye · #6 10-04-2006, 03:14 PM

If I can do it.......

Giraffe · #7 10-04-2006, 03:29 PM

After you pop the top off of the unit, observe whether the tube sockets (the female type base that the tube itself plugs in to) is mounted on the metal chassis (the best way) or on a circuit board (the easy way).

If the sockets are mounted to the chassis, there is little chance of a problem, because the chassis is not going to flex back and forth as you remove the old and install the new. If the sockets are mounted on a circuit board, you will need to be a lot more careful, as a thinner or less-securely-mounted board will flex (bend) back and forth as you worry the tubes in and out, and this could break a trace or a joint somewhere. The first few changes are pretty safe, but over a period of time you can cause damage if you are not careful.

I would say go ahead and give it a try, but follow the advice offered (especially about not forcing things!) and if it looks like the circuit board is bending more than a little, seek some help!

chrisrhoads · #8 10-04-2006, 03:34 PM

what kind of tubes are you replacing it with? I have been thinking about switching out the tubes in my DB750

ajb · #9 10-04-2006, 05:46 PM

Quote:

Originally Posted by chrisrhoads

what kind of tubes are you replacing it with? I have been thinking about switching out the tubes in my DB750

On the advice of Tombowlus, another TB'er, I contacted Doug's Tubes and got three Tung-Sol 12ax7 tubes and an Amperex 12au7 driver. Delivered in two business days. Check out my prior thread (I would cut and paste but I don't know how); Tombowlus put in the link to Doug's website.

Burning_Sphere · #10 10-06-2006, 06:24 PM

I've replaced my preamp tubes myself
I did it for the first time and everything is OK.
Go ahead!

anderbass · #11 10-06-2006, 06:49 PM

Quote:

Originally Posted by ajb

On the advice of Tombowlus, another TB'er, I contacted Doug's Tubes and got three Tung-Sol 12ax7 tubes and an Amperex 12au7 driver. Delivered in two business days. Check out my prior thread (I would cut and paste but I don't know how); Tombowlus put in the link to Doug's website.

Hey ajb, ckeck your messages, I sent you a P/M.

vicenzajay · #12 10-07-2006, 03:43 PM

Quote:

Originally Posted by ajb

On the advice of Tombowlus, another TB'er, I contacted Doug's Tubes and got three Tung-Sol 12ax7 tubes and an Amperex 12au7 driver. Delivered in two business days. Check out my prior thread (I would cut and paste but I don't know how); Tombowlus put in the link to Doug's website.

Great choice...you'll enjoy the difference.

Jay

Fuzzbass · #13 10-07-2006, 05:01 PM

Quote:

Originally Posted by tombrien

After you pop the top off of the unit, observe whether the tube sockets (the female type base that the tube itself plugs in to) is mounted on the metal chassis (the best way) or on a circuit board (the easy way).

If the sockets are mounted to the chassis, there is little chance of a problem, because the chassis is not going to flex back and forth as you remove the old and install the new. If the sockets are mounted on a circuit board, you will need to be a lot more careful, as a thinner or less-securely-mounted board will flex (bend) back and forth as you worry the tubes in and out, and this could break a trace or a joint somewhere. The first few changes are pretty safe, but over a period of time you can cause damage if you are not careful.

I would say go ahead and give it a try, but follow the advice offered (especially about not forcing things!) and if it looks like the circuit board is bending more than a little, seek some help!

Excellent post.

Another thing to be careful of is tube shields... metal sleeves for the tubes. Not all tube gear has 'em, but some do. First time I tried to replace tubes I had a heckuva time trying to figure out how to remove those sleeves. Instead of just screwing 'em off, I had to push down, twist, then release.

shnapper · #14 10-14-2006, 01:07 PM

I hate to rip into someone elses thread, but it's better than starting a new one. My only addition to this I would like to ask is.........

do I wait for tubes to go bad or how does one know when to replace the tubes? Wait until one blows and risk nasty failure or just do it annually or what?

I use my amp about 3 hours a day, practicing and playing, well any help would be great, sorry for poking another thread...........

Fuzzbass · #15 10-14-2006, 04:24 PM

Quote:

Originally Posted by shnapper

do I wait for tubes to go bad or how does one know when to replace the tubes? Wait until one blows and risk nasty failure or just do it annually or what?

What I've learned here in this forum is that the need to replace tubes regularly is a myth. Normally, tubes last decades. Replace them when they fail (perhaps replacing a matched pair if one blows).

shnapper · #16 10-14-2006, 05:38 PM

Quote:

Originally Posted by Fuzzbass

What I've learned here in this forum is that the need to replace tubes regularly is a myth. Normally, tubes last decades. Replace them when they fail (perhaps replacing a matched pair if one blows).

Very cool, thanks for the reply............

Giraffe · #17 10-14-2006, 07:01 PM

Preamp tubes seem to last indefinitely, although there are exceptions. Power tubes wear out, and you can hear the deterioration easily after about six months of heavy use. Three hours a day at bedroom volumes is not nearly heavy use, but don't think the power amp tubes will last like the preamp tubes.

Some players will play a tube amp for years and not notice the gradual deterioration, so they assume "It always sounded like this" but it's not so.