Stereo Simul Class 2:90 blowing B channel fuse

[JAD1971]

Hi,
This is my first post. I purchase a triaxis/2:90 combo. For good measure I sent the triaxis back to mesa for a going over, $250 plus change, thing sounds great. I connected that via stereo outputs with a ADA mp2 preamp to a marshall 1960b cabinet. My impedance is correct on the output jacks, (2)4 ohms into the stereo input on the cabinet.
Playing, the B channel fuse 1A blew. Replaced the fuse, it lasted no more than 2 hours.
Fuses meant to protect indicates WHAT? a bad tube? I dont know, thats why I'm writing. Tell you what, If I lived two blocks away from Mesa in Ca. I'd walk it in and say fix it ,but shipping the 2:90...the thing is heavy.

Appreciate any thoughts on the matter

 

[elvis]

The 1960B is 8 Ohms in stereo. Make sure it is actually set for stereo, or you will drive the two channels of the 2:90 into each other.

It's too difficult to debug this stuff in stereo. Try running only channel B of the 2:90 into the speaker cabinet. Disconnect channel A from the speaker, and set the channel A volume to zero and presence to maximum. See if the ch B fuse survives. Try with cab set to 4 Ohms mono and 8 Ohms Stereo, with the proper impedance connection on the amp.

 

[sendep7]

mine was doing this, i'd hit the standby and there would be a super loud buzzing noise from the b channel speakers then nothing....kept blowing fuses, so i bought new fuses, and swapped the tubes around...then A channel blew...so i retubed the whole darn thing since all the tubes were marked "05" and now shes singin' no problems. i ended up buying 4 duets, in hindsight i shoulda bought 2 quartets. anyway, it looks like it was a bad tube bringing the works down.

Good Luck.

 

[mesa metal]

see if the 290 is set to "line" or "inst" on the back panel......are you using a triaxis and MP2 at the same time...they will definitely conflict with each other if the settings are not right.....and you should be using a cab setup for stereo two inputs right and left channel

 

[Minorprophet]

This happened to me as well a few years ago in my Road King Head as well. It's most definitely a bad tube. Depending on bad the problem is-- sometimes you can see the actual issue in the tube.

 

[SigiZ58]

Just had the same problem. Also for me it was a bad tube. It was a crackeling on the channel when wake up from standby and then bum - blown fuse.
But the tube was recognizable. The glass had lost the silver and head become milky. In normal case it should be to find which tube the problem makes. When you had the channel, then you already had it tracked down to four possible tubes