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Discussion Forum for Mesa Boogie Products
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PostPosted: Wed Jan 13, 2010 3:49 pm 
Mark II

Joined: Wed Aug 10, 2005 6:56 pm
Posts: 66
Location: Parrish, FL
I just came across this old post again and found out through some troubleshooting that the issue was not at all related to the pre amp tube but instead with the speaker A/B selector toggle switch located on the rear of RK head on Ch. 3. I must have bumped it by accident. It caused the exact same issue described by the original poster. It sucks because I went out and purchased new pre amp and power tubes only to discover that the original 6L6 tubes in the RK I heads are no longer sold as Mesa replacement tubes. The newer 6L6s don't have the same bottom end as the older tubes. Hate them!

PostPosted: Thu Jul 07, 2011 9:32 am 
Mark III

Joined: Tue Jun 22, 2010 9:20 am
Posts: 244
Found this info over on a JVM forum. the 11th post down here

Here is important information I´ve got from New Sensor in reply to my latest inquiry:
"The Electro-Harmonix 12AX7EH has a spiral filament and should not be used in cathode follower circuits. The Tung-Sol 12AX7, Mullard 12AX7, and Sovtek 12AX7LPS also have spiral filaments."

That would explain reported failures in V3.

The guy from New Sensor recommends Sovtek 12AX7 WA and WB:
"The most rugged 12AX7 types for cathode follower service are the Sovtek 12AX7WA and WB."

I will give the Svetlana a chance and eventually report its failure, incremental noise or any other symptom.

Very best,

ESP Eclipse II w/EMG JH Set
Squier Bullet w/SD SH-2n/SH-6
Mini Rectifier
2x12 Horizontal Cab
Line UX6 w/ Overloud 2

PostPosted: Mon Mar 05, 2012 7:11 pm 
Mark III
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Joined: Wed Feb 10, 2010 12:07 pm
Posts: 329
Location: Marysville, California, USA
I am thankful for this post as the V4 in my Heartbreaker fits this discussion.


Mark III no mark w Randy's initials & some IIc+ parts
50 Caliber (6BQ5) 4xEL84
Fender 75
Acoustic 165

1970 LPGT
1981 The Strat
1983 GZ-300
1983 (Elite Neck)/2001 FrankenStrat
1990 Firebird
more guitars, so little characters

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