My RK2 Died

[Ken in NC]

Guys, this is probably an easy problem to fix, but I would like to post for your thoughts and suggestions.

Last night at a gig, my RK2 died. The sound of the amp (all evening) was just not right. I heard that the tone was not what I was used to and the amp sounded to be in a state of flux. Well... about the 5th song the amp lost all volume. This was preceded by crackling.

I was using Channel 3 on my RK2 and then.... NOTHING.. I quickly switched to Channel 2 and had volume for about 10 seconds and the problem creeped in there as well.

Today ( as I have nother gig this evening) I am running through various tubes using the Progressive LInkage to see if I can bypass the problem and identify the faulty tubes (if it is tubes).

I went to 6L6 and no volume. EL34's - No Volume. nothing. I figured that if the problem was a power tube problem, I could see if running the EL34's would identify that it might be a 6L6 problem and visa versa. Regardless of the Power tube I selected, the amp will not make any sound.

How can I tell if it is Power tube versus Preamp Tube? I figured that if it were preamp, I would at least hear some sound. Right?

I am leaning towards the Power Tubes as being faulty, but I thought that switching the linkage would at least get the amp to sound by going through the tube choices. Would a dead 6L6 cause the linkage setting of 2XEL34's to not work?

Any help would be appreciated as I would like to use the amp this evening. Thanks!

Moderator edit: Please watch the language.

 

[phyrexia]

Fuse still good?

 

[lockbody]

Using the tube rectifier? Checked them?

 

[Ken in NC]

I think so. If i crank the amp to full volume, I can barely hear my guitar. I am thinking that if the fuse was bad, this would not happen.

 

[Platypus]

Check your preamp tubes

 

[Ken in NC]

Here's the scoop.

I replaced the 5U4 tubes with the stock boogie tubes.... Nothing.
I replaced the EL34's.... Nothing
I replaced the 6L6's.... Nothing

Ok - so much for the power section, huh.

Started looking at the 12AX7 tubes. Removed the aluminum sleeves and found that V6 was broken. Odd. A preamp tube broken in the aliminum sleeve? Also the top of the tube had a "frosted" look to it.

Replaced V6 with a 12AX7 and the amp is functional again.

I originally thought that a 12AX7 would still aloow the amp to produce some "sound" but apparently the V6 tube was indeed the culprit and the Power Tubes are still fine.

Thanks for the feedback and recommendations, guys. THis board is always helpful to boogie owners.

 

[Platypus]

Hahaha.. I was seriously going to post that it prob had a broken preamp tube.. a lot of people with RK2's seem to report this problem plus the symptoms of the problem all point to preamp

Glad it was an easy fix and you're back up

 

[disassembled]

I don't like the sound of this. I know BB reported a few "blown" pre tubes which before the RK I had never heard of and would call BS on up until now. Pre tubes are really tough and aren't subjected to harsh operating conditions like power tubes are. The voltage and current are part of the equation for the tone you're getting but this seems a bit rediculous for the amp to break tubes.

I hope the problem is related to careless transport as opposed to running the pre tubes at their max.


I hope this doesn't happen in the future but you should call and tell Mesa every time it does just to let them know.


Greg

 

[ThunderMonkey]

I'm thinkin'.....hmmmm....kinda hurts when I do this so I'll try to make it quick.........

the V6 on a RK is the Phase Inverter pre, right?

If this isn't a "balanced" preamp it just works one side of the triode (as they have twin triodes.
This could be the culprit in this case and finally just gave up as it was working too hard to do the job of two ! Phase Inverter driver (12AX7) is very important and some say to replace these every time you change power tubes cause it gets hammered. Supplying good balanced pregain to the tubes, very important in tone quest.

I'm also thinkin' this might be an overall problem we always seem to run into when it comes to missing something in a frequency that we can't quite put our finger on.
Say in V2 or V3 where the circuit is using both sides of the triode for eq tone, if they are unbalanced you still get good use but you're not getting full potential or best case scenario performance from that 12AX7.

I guess we need to start demanding they test these for good balanced spec like Bob from Eurotubes does.

 

[Ken in NC]

I don't like the sound of this. I know BB reported a few "blown" pre tubes which before the RK I had never heard of and would call BS on up until now. Pre tubes are really tough and aren't subjected to harsh operating conditions like power tubes are. The voltage and current are part of the equation for the tone you're getting but this seems a bit rediculous for the amp to break tubes.

I hope the problem is related to careless transport as opposed to running the pre tubes at their max.


I hope this doesn't happen in the future but you should call and tell Mesa every time it does just to let them know.


Greg

I run the gain on my amp about 2 o'clock which isn't real high. So, i do not think I am pushing the preamp tube all that hard. However, transport may be a culprit. My RK2 is a combo with casters and i hate Carrying it, so I do roll it quite a bit. The puzzler is that it was working through sound check and the first 5 songs of the set before it died. I would tend to think that if transport was the "real" core problem, I should have seen this when powering the amp on after setup.

Anyways, yeah - I was very surprised to see the tube broken.

 

[Boogiebabies]

Shocking. I have been through 5 V1's on my RK II and RK II v.2. The V1 is behind the OT.

The glass on the Mesa Chinese 7025 SS is too thin and on cool down the glass cracks.

 

[fbomb]

transport is most likely the problem. back in november i bought a new stiletto,in a seald box,had the same symptoms as your amp,turned out to be a cracked preamp tube.i wish i would of seen this thread sooner,maybe i could have saved you some money you spent on all those power tubes.

 

[Ken in NC]

Shocking. I have been through 5 V1's on my RK II and RK II v.2. The V1 is behind the OT.

The glass on the Mesa Chinese 7025 SS is too thin and on cool down the glass cracks.

I replaced the 12AX7 with a Groove Tube. The glass on the Groove Tube does appear to be a lot thicker. When I pulled the original broken tube out, I was quite surprised by how thin and brittle the glass was.

 

[Ken in NC]

transport is most likely the problem. back in november i bought a new stiletto,in a seald box,had the same symptoms as your amp,turned out to be a cracked preamp tube.i wish i would of seen this thread sooner,maybe i could have saved you some money you spent on all those power tubes.

fbomb

I think that transport may have been the culprit, but the amp ran through sound check and part of the performance before it went belly-up. Are you thinking that the tube heating up simply exploited a flaw which may have happened during transportation?

As for the power tubes... I'll need them sooner or later as I use the amp a lot. No worries on that purchase.

 

[CudBucket]

I think so. If i crank the amp to full volume, I can barely hear my guitar. I am thinking that if the fuse was bad, this would not happen.

Mine sounded exactly like this when I took it out of the box. Bad pre in V2.

 

[Cowbell Fever]

Nice language Captain Spaulding[/quote]

 

[lactose]

Thanks for the post. I will remember to remove the shields and check the preamp tubes if something goes wrong.

I lost sound for about 30 minutes the other day, but traced it down to a bad effects send cable.

 

[massydual]

in any case, a high use of a preamp tube leads to a mechanical failure of the glass...never...for sure it's a transport problem or the spring inside the aluminium cap is too strong...

 

[abecon5]

about the 5th song the amp lost all volume. This was preceded by crackling.

yep, if you hear any crackling, (this is more obvious in the clean Ch) just do yourself a favor and change the pre amp tubes asap. I learned the hard way and had mine die out during a gig too.

 

[Ken in NC]

I had literally seconds before the crackling turned into silence. I was standing there and the soundman was pushing the faders and looking at me. I was just laughing...

Anyways, new Groove Tubes are replacing the current faulty tube aqnd the show the next night went well. My amp had its tone back (which was missing for about 2 - 3 shows) Something just wasn't quite right. I couldn't put my finder on it.

It's funny. You'd think that after 20+ years of playing, your ears would tell you that tubes need to be changed soon, but you never know WHICH tube needs it until it fails. :evil: :twisted: