My Mark V died and I don't think its tube/fuse related.

[Schecter6505]

Hey guys. I have had my Mark V head for about a year and a half. Other than replacing a couple of bad tubes since I have been using it, I haven't had any issues until a couple weeks ago.

I turned the amp on to warm up for a few minutes when I noticed a "hot" electrical smell and immediately reached over to turn the amp off. Before I could, it lost power completely. I let it cool down and replaced the fuse with a new one and flipped the power switch and nothing happened except that I hear the fan running. I'm not getting any lights or any noise from the amp at all. I've tried other power cables, a complete change of tubes and other new fuses and I'm not getting anything.

I was wondering if any of you guys know what I'm up against here???

I'm guessing it could be anything but I don't know enough to even attempt to find the problem. I think I'm gonna send it off to Mesa regardless (its about 5 months out of warranty - lucky me) so they can go through it.

Thanks,
Tommy

 

[bandit2013]

Did you replace the Rectifier tube? If not you can remove it If you operate the amp in 90W mode. If there is a short in the tube rectifier, nothing will power up on the high voltage side. Sometimes it does not even blow a fuse and ends up pulling every thing down to about 6V. When the rectifier tube shorts out when the supply is at full power, it will blow the fuse. That may continue to happen depending on the type of short in the rectifier tube.

If that does nothing, check fuse. You can remove the power tubes and power it up just to check if the lights come on. It may be probable for a preamp tube to cause this but not as likely as the Rectifier tube or power tube. I had something similar, I could not get the amp to power up and fuse was remaining intact. Removed all the tubes and installed a set of known to be good tubes (I usually keep spares on me) but the power tubes were EL34 and not 6L6. Not sure if the change in the bias switch had a role in this but the amp fired up just fine. Went back to the same 6L6 tubes but new Rectifier and all was good. Never had that occur again.

If that does not correct the issue, probably best to send in for check up and repair. If it smells like burning phenolic usually associated with some bluish white smoke, would be a screen resistor (carbon composition encased in phenolic resin) on one of the power tubes. Very nasty smell if you do not know what burning phenolic smells like, quite nauseating actually. However, the amp should power up and operate without the screen resistors but it will sound terrible, may even cause the opposite tube in the circuit to red plate.

 

[BrownieD2W]

Make sure you can see the Tubes when you turn on the amp the next time. Watch them as soon as you flip the Power Switch and again when you flip the Standby Switch. I would also recommend trying the 90-watt mode to be sure. It could be a blown grid-resistor as well, I had similar issues right when I shorted a Tube that took out a Resistor on its way out.

 

[IronSean]

The same thing just happened to me: I blew a fuse, replaced it and everything looked good, then suddenly nothing would light up or turn on. The only thing I get when I power up is the heater filaments turn on, but no lights on the front panel or sound.

I still had warranty though, and even an extended warranty from the store to handle shipping to/from Mesa, so I just did that rather than doing a lot of troubleshooting myself. I didn't even bother taking the chassis out to see what the issue was, but I'm hoping they tell me when they figure out.

 

[Schecter6505]

Thanks for the input, guys. I have tried everything recommended here to no avail. My amp is off to California for some love.