mesa boogie 400+ burning power tubes HELP! PROBLEM

[jroutensowhat]

the minute you turn the volume up on my boogie 400+ the powertubes glow super red hot..... immediately i switch it off.
the issue keeps happening (just on 2 other short tests)
does any body have/had this problem or could help me locate the problem.... is it a bias issue and how do u bias this amp as its fixed?
thanks
j

 

[JonPol]

check the fuse, might need replacing

 

[B-string]

It sounds like a bias issue, yes it is a fixed bias amp as are most. It has no user adjustment is probably what you meant? The bias circuit may have a fault or you could have other issues. That is a nice amp to take chances with, get it to a tech quick before major damage gets done!

 

[beans-on-toast]

The bias circuits for the 400+ are shown in the lower right corner of the schematic below. Node D, -54 VDC is the power tube bias circuit. One of the components in this node may have a problem. Your tech should see if they are up to spec. Also a 15V zener diode (5352) is used to drop the screen voltage on the power tubes. It would be a good idea to check that it is working properly.

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[JimWasHere]

Something tells me you should be prepared to retube the power section after you have the amp in to the tech... That's some serious wear they're accumulating real fast. Also, if I remember right, isn't there a tube troubleshooting section in the manual for that amp? That may help you.