Don't flame me -dumb question from a tube-newbie!

[Digirat]

Now you're all going to laugh at me :!:

I've got an Express 5:50 1x12 combo and while I had the protective grill off to check something else out, I had a good look around inside. I can see how the 6L6s can be accessed and removed when replacement becomes necessary, but I'm a bit confused about the pre-amp tubes!

After reading the manual and the stuff about diagnosing pre-amp tube problems by tapping on them etc, I was a bit surprised to find that the 5 12AX7s are hidden away inside silver cylinders (I presume for protection?). If you are going to do the tap-test, doesn't that have to be direct on the tubes themselves?

The main reason I'm asking is because I wanted to try to remove and put back one of the 12AX7s, just to see how easy it was (see - I said I was a tube-newbie!!). I tried "simply pulling out" the tube as described in the manual, but it didn't come out easily. I didn't want to damage anything by being naive/dumb, so I wanted to check with you non-dummy guys first! Do you first have to remove the protective cylinders by unscrewing or something first to get at the tubes :?:

Thanks, and sorry if this wins "dumbest post of the month" award 8)

 

[Platypus]

Don't worry digirat, we all have to start somewhere

The silver tubes are heat shields, they twist off with a quarter turn. Once the tube cover is off, the preamp tube can be removed simply by pulling down while simultaniously wiggling the tube left and right. It should come fairly easy, you should NEVER use much force.

 

[yettoblaster]

Miniature tube shields like on Fenders and Mesa's have little dimples pressed into the shield which correspond with tiny short pins on the lower section that stays on the chassis.
The shields sort of rotate on a bit as you push down against spring tension.

They come off the same way: you push down towards the chassis a bit and rotate a bit to the left (if your amp is standing on its head). Then they will come off from the spring tension once you've cleared the pin notches.

Twist off: twist on: but with a bit of pushing down towards the chassis helps spin 'em past the nibs.

Then with a bit of wiggling the tubes pull straight out. Notice the missing pin: that's the index when you put 'em back in so the pins will go into the socket right.

 

[JamesD]

Don't feel dumb, i looked at the heat shields weird when i got my recto. Everything Platy said is spot on. Enjoy!

 

[RR]

Your's a combo so I would set your amp upside down to put back the preamp tubes.

I was so impatient trying to get the preamp tubes' pins back in the sockets, I would take the time to remove the entire chassis from its enclosure and then put the preamp tubes in then put the chassis back in it enclosure.

 

[Digirat]

Thanks guys for all the help and advice!

........ and for the complete absence of napalm :lol: :!:

 

[clutch71]

+1 on flipping the amp upside down. The tubes will fit snug. Watch when you pull them out so you don't inadvertently smack one against speaker magnet. Did that with a power tube on and ROV...and against the metal grill on a DR too. Fortunately neither time broke a tube.

All part of the learning curve. You were much better off stopping where you were at and asking for advice.

 

[Beserkr]

+1 on what yettoblaster said, and if you pull the power tubes the plastic tit in between the pins is a key so it can be reinstalled correctly. Take care when removing the power tubes not to wiggle them as you can easily break off the key.

 

[yettoblaster]

...Take care when removing the power tubes not to wiggle them as you can easily break off the key.

Excellent advice.
"...I've done that, man!"

Hey Berserkr, ever eat burgers at "P.J.'s" before it burned down, in the 60's?
(I have a cousin in Pittsford)

 

[Beserkr]

Thanks yettoblaster, and as for P.J's I didn't move to New York until '95.

 

[yettoblaster]

Ah.

I grew up in Schenectady and the Finger Lakes, with cousins in Rochester.

Oh well. After it burned down I heard they found lotsa horsemeat. I think I've been missing that in my burgers ever since. 8)

 

[Beserkr]

They said it was horse meat, but I think it was probably Jimmy Hoffa :lol:

 

[yettoblaster]

Gak!
"Puh-too-weee!..." :shock:

 

[RR]

... AND MAKE SURE THE AMP IS NOT TURNED ON AND BETTER YET, UNPLUGGED IT 130 dBs

... <cough> ... uh ... I feel better,

 

[theaero]

You have to romance the tubes... coax the tubes... BE THE TUBES...




Oh come on... we've all been there

 

[nemesys]

Just be careful when you're romancing your tubes, you can get a nasty electrical shock doing that.

 

[dodger916]

..not to mention painful burns :x