Nooooo!!!! Power issue with Mark IV

[lerxst88]

I just got this thing 4 days ago! So today I went to jam on it since no one would be home and decided I might as well crank it. I loaded it with a quartet of 6L6s and flipped on the power to full. I had it set in pentode mode and when I flipped standby I got some buzzing and immediately turned standby off. I tried it again and saw that the two right tubes glowed bright blue for a sec while the buzzing was there so i shut off standby again. I tried in Triode mode and it powered up normally. I proceeded to crank it (to only 4 haha) and played for probably an hour. After jamming loudly I turned it down and messed with settings. I replaced the two outer 6L6s with EL-34s and played for a while and heard a weird "pop" sound like when you turn on a solid state amp but the amp kept going and didnt show any bad signs. A few seconds later, all the red LEDs came on dimly and I heard a weird buzzing. Its kind of hard to remember exactly what happened because I just about crapped my parts when that happened!!! I tried to shut it off but accidentally switched into Tweed mode where the amp went back to normal.

I should mention I have been using Tweed mode and 6V6s for about 60% of the time I have had it.

Im thinking it might need filter caps. anyone else wanna chime in?

 

[lerxst88]

Ok after some more testing it only does it when I have the sovtek 6L6s in the middle two slots and in Simul-Class and Pentode mode.

Im suspecting maybe the sovteks the guy I got it from put in are just crap tubes and arent designed to run in a simul-class amp.

anyone use anything but mesa tubes in their amps?

 

[swbo101]

I have only ever used Mesa power tubes. Now you CAN use others. However, since their amps are a fixed bias, you need to be sure that those tubes fall within those specs. If your tubes were glowing blue that tells me that they do not fall within that range. If you buy NON Mesa tubes, you need to purchase them from a reputable place that is aware of the bias range that these amps run under. I would try to get some Mesa branded tubes or call one of the better tube dealers and let them know what amp you need these tubes for. They should be able to get you the right ones. Also if you want to use 6V6's they can ONLY be used in the Mark IV in tweed mode running in Simul-Class and you should also plug an 8 ohm speaker into the 4 ohm jack in this setting.

Hope this helps.

 

[topcat0399]

Ok after some more testing it only does it when I have the sovtek 6L6s in the middle two slots and in Simul-Class and Pentode mode.

Im suspecting maybe the sovteks the guy I got it from put in are just crap tubes and arent designed to run in a simul-class amp.

anyone use anything but mesa tubes in their amps?

so what happens if you put the sovteks in the 2 outter sockets and run on class A tweed?

same issue?

Just curious.

 

[lerxst88]

Same issue. I think for now I'll just leave it in class A and triode and make the tubes last as long as possible.

When I get down to school, I may crack it open and make sure everything is hooked up right and nothing is fried

 

[topcat0399]

Same issue. I think for now I'll just leave it in class A and triode and make the tubes last as long as possible.

When I get down to school, I may crack it open and make sure everything is hooked up right and nothing is fried

"cracking it open" only takes minutes - its very simple to do. I always lay mine on its side - easier to slide out, tubes and all. Just have to watch out for the FAN Cable (unplug it - a little hard to get at).


Good Luck with it.

I adore my Mark IV

 

[lerxst88]

I have actually already taken in apart for a look see. There's a LOT of stuff in there!

I agree with you! The mark iv is amazing and nothing like what I expected! I got from Queen to 3 Inches Of Blood to Eric Johnson to Pink Floyd tonight without changing any settings! Truly a remarkable amp.