Crackling sound coming from my Mark IV

[bloodbath666]

I'm using JJ el34L's and 6l6 tubes in my mark 4. Bob at eurotubes picked them out for me. He said run two el34's on the outward sockets and 2 6l6's on the inward and run in Simuclass mode. I've been using the stock mesa power tubes lately, and decided I'd try my jj's again. Well when I put them in I'm getting this crackling and popping noise it's really quite terrible. I look at the tubes in the back and they are glowing fine, and all the preamp tubes seem fine. I replaced one of the preamp tubes that wasn't shining as bright, but still that **** crackle.

Anywho, this doesn't happen when I have the stock mesa power tubes in only when I put the JJ's in. Any suggestions?

BTW- My stock mesa power tubes seem to be running fine, but they are starting to get kind of a blue type glow. I know when a tube blows, the have kind of a blue tint to them. Is this normal or do I really need new tubes?

 

[stokes]

Blue glow in the power tubes is not neccessarily a bad thing.Most times it is harmless.Somebody posted a link to a paper on the subject.I'm not sure off hand where it is,if I can find it I will pass it along.I have had tubes that had the blue glow and they lasted as long as would be expected.I think when the blue glow is indicative of a problem it is present in the entire tube and has a sort of white haze associated with it.

 

[stokes]

From "Sylvania Engineering Data Service", vol. 1, pg 23 (1960?):

BLUE GLOWS

Blue Glows are not tube detriments per se. They are, however, suspects in the eyes of many receiving tube users for lack of a full understanding of their origins. There are several types of Blue Glow which can be described as follows:

FLUORESCENCE-this type of glow is usually violet in color and most noticeable around the inside surface of the glass bulb. It is most pronounced on power tubes and is the product of electron bombardment of the glass taking place within the tube. It generally has no adverse affect upon receiver performance, and in fact, tubes displaying this phenomenon are particularily good with respect to gas content.

MERCURY VAPOR HAZE-is a blue-violet glow associated with those tube types which rely upon mercury vapor for proper operation. In such cases, the blue glow should be evident indicating proper operation.

GAS-produces a blue haze, generally confined to the vicinity of the mount structure. The proper function of gas types such as thyratrons, voltage regulator and voltage reference tubes, requires the presence of this glow as an indication of proper tube operation. Some voltage regulators use neon instead of argon and as a result exhibit a pink-orange glow. It is, however, a distinct detriment in vacuum receiving types, where the presence of gas in large amounts can cause malfunction of the equipment.

Submitted by:

Doug Haugen

Couldnt get the link to work but here is the text.

 

[6L6C]

I'm using JJ el34L's and 6l6 tubes in my mark 4. Bob at eurotubes picked them out for me. He said run two el34's on the outward sockets and 2 6l6's on the inward and run in Simuclass mode.

I run my amp the same way but it runs fine have you tried running just class A so just the EL34’s are active? If you don’t get crackling running this way it might be the 6L6’s if so grab two from the original set run them with the 34’s and see what happens. New tube or not it might be a bad tube!
However if you do get the cracking with the EL34’s running class A maybe you can barrow 2 EL34’s from a friend for a quick experiment.
When your swapping power tubes out (don’t forget keep the sets together)

 

[bloodbath666]

Hey, thanks for all the help so far guyz. I'll try running my JJ's in class A I haven't tried that yet. It won't hurt the amp to run in class A will it? Bob was telling me to run it simuclass. Thx for the info on tube color as well stokes.

 

[stokes]

If the crackling only happens with the JJ tubes and not the Mesa's then it makes sense that it is not your amp.Do like 6L6C says and try to find out which it is,the EL34's or the 6L6's.

 

[6L6C]

Hey, thanks for all the help so far guyz. I'll try running my JJ's in class A I haven't tried that yet. It won't hurt the amp to run in class A will it? Bob was telling me to run it simuclass. Thx for the info on tube color as well stokes.

Yeah even with 2 EL34’s and 2 6L6’s you can run class A Pentode or Triode, full power or tweed power. The only time you have to watch your power settings is when using 4 6V6’s, then your only supposed to run simuclass only and tweed power only!
And to reduce wear on the 6V6’s Boogie recommends 8 ohm speaker load into the 4 ohm output jack