Problems with my Mark V

[kbzon77]

Sorry for the double-posting but I am new here and I need help!

Dear Srs.

A few days ago, finally my MB Mark V arrived to my home (Chile). I bought this amp from ebay one month ago. A friend of mine bring it to me personally, but he doesn't put out the tubes from the amp when he returns to Chile.

Here, I bought a 500 W step-down transformer and connected the amp and then selected channel 1. Really awesome !... later I moved to channel 2 with a little more gain, and 10 minutes after that the amp loss gain and weight, the same features on channel 3... I turned it off, but later was the same thing.

Is this associated to a damage of tubes, power o preamp??... I want to buy a tubes replacement.. do you thing Mesa boogie are the best? ... have they kits for Mk V?... or should I buy 2 duets of 6L6 GC + 1 5U4GB + 7 12AX7 ??

Please help me .. this is the dream come true but I can not play yet..

Thanks for your help

 

[kbzon77]

A few minutes ago I was playing. I changed the transformer by one of 1000 W... I cleaned the contacts of all tubes in the afternoon too.
But, the problem is the same... channel 1 es very clean but if you play hard has a little hum, but the channel 2 and 3 is muddy, with a lack of gain, I mean has gain but badly distorted, with a different tone compared when I played the first 20 minutes when the amp arrived... and compared with so many videos on youtube for example

Please help, I am very sad right now... all my work only for see the amp...

 

[domct203]

What type/brand of tubes are in the amp? If the powertubes are not within Mesa specs you could be doing damage to the amp.

Your choice to change to a 1000W transformer is a wise one. At loud volumes the power supply of the amp can draw well over 400W.

Dom

 

[K-Roll]

sounds like preamp tubes