Skip to content
Clear all

Tube Amp

3 Posts
2 Users
Active Member
Joined: 8 years ago
Posts: 3
Topic starter  

Howdy, all
Newbie here, looks like there may be knowledge to be gained,
So here goes....
Bought a Randall RD40c last year....It's no MesaBoogie (sigh)
Came with Ruby Tubes (junk)
Just popped in New JJ tubes, SUPPOSEDLY best you can get
according to my sources. Now, it crackles like hell
Totally bummed. (4) 12ax7 preamp and (2) 6L6 power
is it possible to install the power tubes incorrectly, yet still produce sound? idk
I am thoroughly disgusted, and disappointed. Its getting late and I need some rest
work in the morning. I saw reseating might do the trick, but I will try that tomorrow, after I call
a local, knowledgeable tech. Never had this problem with the Boogie....the Randall is self biasing.
any input would be most helpful.
Thx in advance :wink:

Reputable Member
Joined: 18 years ago
Posts: 397

is it possible to install the power tubes incorrectly, yet still produce sound? idk
Aren't tubes indexed to the sockets so you can't install them incorrectly? Maybe a tab on the the cathode so the tube can only be inserted one way? I think if somehow you were able to insert them so the pins weren't all where they were supposed to be, it just flat wouldn't work.

Does it crackle all the time, or only if you turn a control or do something else? Could it be a flaky connection in your cable, or in your guitar's output jack or the amp's input?
I'm somewhat inclined to think it's not the tubes, but I'm no electronics technician. If you've had it for awhile, maybe a shot of DeoxIT on the controls will clear out the scratch. I bought some from Stewart-MacDonald last year, along with one of their Pot Cleaning Caps. (The stuff comes out of the can pretty cold, so don't let it get on guitar finishes or other places where it might crack something.)

Good luck with eliminating the crackle.

Active Member
Joined: 8 years ago
Posts: 3
Topic starter  

:P Soooo
Back to the tube issue....
Here is the Solution! The Randall has very flimsy Tube Shields, which can be easily mangled if not handled correctly and very gently. My dumb A&# mangled the paper thin top of one of the Shields, which has 2 long springs 180 degrees apart from it to hold it (tube) securely. This is designed to reduce the tubes from going microphonic. That's ok, because I really don't have that problem... Secondly, the tubes only go in one way, period. Guess I got lucky there, and didn't bend any of the tynes!

Spent $9 on a can of Contact cleaner, blasted the sockets, reseated the power tubes, and Voila, totally badass! No need for the shields, lots of folks disregard them, even if the tubes are upside down, as is the case with the Randall. The shields trap heat as well, which reduces useful tube life.
Could I tell the difference between the Ruby and the JJ tubes? Not really, but next month I am replacing the speaker with an Italian Jensen Electric Lightning....should never, ever, sold the MesaBoogie.