Mark V decided to just....die

[Mark V]

So, I was pulling some mean leads during band rehearsal, when all of a sudden I had no sound comming out the Mark V... I looked at the amp just in time to see that all the lights got turned off....
Then a HUGHE amount of white smoke emerged from the back of the amp (head version), and the whole place smelled of burnt electronics...

I have no clue what happened... The fuse blew that's for sure, but seems that whatever caused it, took out some other parts (transformer maybe?).
Luckily the amp is still two weeks in warranty, so I dropped it off at the shop and they were going to send it to the importer (not sure if they'll send it to Mesa).

Anyway, the Mark V is a cool amp and all, but it seems to have some serious issues though... Before I had the head version, I owned the Combo version, and that one would blew fuses every so often...and I could never really find a reason why (nor did the shop where I bought it).

Guess I'll be selling this one when it's fixed.

 

[Old BF Shred]

Just curious...did you try to pull out the output tubes to see if it still blew a fuse? If not then it may be just a shorted tube that took out a screen, or depending on mode, cathode or plate resistor.
Still needs service, of course, but it is not an uncommon issue and does not mean you have a "lemon".

But I understand how discouraging this could be.

Good luck with that!

 

[jb's 52]

If you're blowing through fuses like that on two different amps, I'd check for
something in common. In this case, I'd check the power supply you got
both powering each amp. Could be that you have an outlet and power that
surges frequently.

 

[Authorized Boogie]

If you saw smoke or smelled burning - its a screen resistor that got taken out when a power tube shorted. Its not uncommon with a severe short, and should be a simple replacement by a technician. Do not use the amp until the resistor is replaced or you will continue to have issues, as the screen current will run out of control without the resistor in place.

 

[Mark V]

just fyi: the fuse was still intact.

Got it back from repair (took over a month), it's working again now

 

[Mrjason]

If you're blowing through fuses like that on two different amps, I'd check for
something in common. In this case, I'd check the power supply you got
both powering each amp. Could be that you have an outlet and power that
surges frequently.

No doubt! I wouldn't plug another amp into the same power source until I checked it out! Mesa's are built like tanks.

 

[bandit2013]

Letting the genie out of the amp is not a good thing. I have not done that yet but I must have pissed him off some since I kept red plating tubes until I fixed a different problem, intermittent load due to defective switch on 8 ohm jack (connects the two parallel 4 ohm stereo loads to series for 8 ohms when speaker plug is inserted into 8 ohm jack. Took me several tube replacements due to premature red plating to make the change on the speaker jacks on my Recto cab. Mark V was new, cab was 14 years old (well kept but spent most of its time in storage, I am the original owner of the cab so I know its history and how it was used and stored). Since the change, I have yet to red plate a power tube, now going on almost 2 years and no problems). Also checked the 8 ohm jack switch, did not take much to get it to disconnect.

This may not be the root cause of your issue. Probably is not common either to have intermittent load on your amp from a Mesa cabinet. If it was common, there would be more complaints on the issue. It is also something easy to overlook.