RK II preamp tubes

[daveythomas]

There are 6 12ax7 preamp tubes in the road king (v1, v2, v3, v4, v5, v6). Anyone know what each of these is responsibe for?

I just got my RKII on Friday. Sunday, CHs 3 and 4 faded in volume over a period of two to three minutes and were then very quiet. I pulled out the manual and thought that it might be the preamp tubes since it was only happening on certain channels, and I had tried the different power amp tubes with all the channels and found the same results.

So I started pulling preamp tubes and switching their positions. I did things like V1 for V5, V3 for V4, and so on. One time I lost all channels, another I lost the reverb, and another I lost CH2. The first mistake I made was not labeling the tubes so I could put them back in their factory order.

Here is the thing. The way I have them in now, everything works. Any ideas? If I have a bad preamp tube or two, would it be possible to have everything work if the bad ones are in lower gain positions?

Do you think there is a problem? Should I get them tested?

 

[tele_jas]

I'd call the store you got the RK at or call Boogie and tell them about the problem and that you've swapped tubes around and lost some sounds (reverb, volume, ect..) with some swaps and got them back on other swaps so you're pretty sure it's a preamp tube. See if they'll give you some new tubes. Boogie has a warranty on the tubes on new amps (only good for a certain amount of time like for 90 days or 6 months or something like that).

 

[Flavell777]

Just to add, if it seems to be working now it could be a drive issue with a tube. If this tube is now in the phase inverter position ie. controlling the power tubes push pull, you won't notice the loss of volume however you may end up shagging the power tubes. Get it to the store and get them to change the pre amp tubes asap!

 

[Platypus]

Willing to bet MB will mail you a new set for free.

 

[CudBucket]

My RK2 came with a broken preamp tube. Today, I received the 4 new replacement tubes from Mesa.

 

[MadisonV44]

Hello Thomas, have you got any update on this issues ? Is it still working since you've made the switch ? Did you finaly replace the preamp tubes ?

I've got exactly the same problem on my RK II.

I upgraded from a RKI to a RKII that I received yesterday
My first impression was that It sounded good but more straight and with the feeling that it was not getting into clip very easy and it was less legato and easy to play compared to my old RKI.

The day after the volume suddenly droped while playing on CH3 (CH1& CH2 stay unaffected). My two high gain chanels 3 & 4 are now very quiet as you describe it in your post.

Your feedbacks will be much appreciated.
**** fragile tubes !!! but holy sound !

JB

 

[MadisonV44]

Today is a great day ...

After a long one by one 12ax7 test I finaly found the guilty and replaced it ! The described issue in my last post was related to a single preamp tube !! (volume suddenly droped while playing on my RKII CH3. Channels 3 & 4 were then affected with almost no volume)

Thomas many thanks to U. Your precise description helped me to fix it quicky ! My local dealer was also very helpfull by giving me 6 brand new 12AX7...That's what we can call Total client care and services ...

 

[daveythomas]

Awesome!!!

I called Mesa on Thursday and they are sending me out replacements for my preamp tubes. I will put them in and give them a test.

I talked with Mike Taylor about having switched around the preamp tubes and he said that was the first thing he would have suggested, other than switching one out, one at a time with a known good one.