Mark V combo issue

Hello all, I'm hoping someone can shed some light on a problem I'm having with my Mark V combo. I bought it new and have it less than a year, and it started making a terrible hum/buzz. Happens as soon as I take it off standby. On all channels, with loop on & off, and on all wattages. Even if I unplug the guitar. HOWEVER, the 1st time it happened, I shut it off, waited, turned it back on, and all was right with the world. Today it did it again and after turning it off then back on, then checking channels, turning off n on again......... Still just a loud hum/buzzing going on. Finally after turning it off and, reluctantly, turning it back on, it worked just fine. What could it be?????

It could be an intermittent short in one of the power tubes. when you're playing the vibrations will shake the tubes and if something has come loose, it'll short.

When it starts humming again take a look in the back and see if one of the tubes is red plating (it'll be glowing like a toaster element). Replace that tube and its pair.

Sometimes you can force the issue by tapping on the tubes while the power is on.

No red plating tubes either. And it's right when I turn it on. Nothing playing at all when it happens. The fact that it eventually stops and works is what's driving me nuts. But no power tube red plating. :|

You could have what is a "cold solder joint" basically a place that is soldered that is not making good connection. Things didn't actually bond when it was assembled. So when you first turn on the amp it is cold and there is a bad connection at a solder point but as the amp warms up or is vibrated right, it makes connection. Then once the amp warms up it will continue to make connection. Metal expands when it warms, contracts when it cools and the circuit board is pretty stable. It is not uncommon.

I actually work around people that do this stuff (aircraft R&D). I have seen technicians go back over a board with a soldering iron on a board that worked fine the day before.

But, even I would take it to Boogie. That is a warranty issue plus when they go through it if they see anything else, like an incorrect reading somewhere or another questionable solder joint they will fix that too.

Thanks OTM. I appreciate the reply. This morning I turned it on............ Nothing but soul satisfying tone!! I'm not complaining, but it is strange.

Other than what was stated... Power tube, Rectifier tube (yes this will cause issues but usually blows fuse but may result in a noisy power supply which will lead to audible noise), solder joint, loose connection in the tube sockets. I may be preamp tube. One thing to note, if a preamp tube is making noise, it does not always have to be in the signal chain if you hear it.