Looks like one of my output tubes may have gone into runaway, red-plated, and then likely shorted. Following this incident there is a rather loud low frequency hum when the amp is taken off standby. Given that the amp is under warranty I took it down to the local Mesa authorized warranty service center to be repaired / resolved. They'll have it for a week or so. I have my Fuchs ODS to play through so I'm a long ways from high and dry while the Mk V is out for service. I'll miss it while it's gone just the same.
Mark V in for service - likely an output tube failure....
- Thread starter Deaj
- Start date
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MusicManJP6
Well-known member
scoden said:
Definitely. And, good call taking it to a tech!
MusicManJP6 said:
Yeah, I have no plans to become familiar with the chassis' contents until the warranty is over. Given the complexity of this circuit I will almost certainly have any post warranty service needs handled by the local service center. I've seen gut shots of the MkV and I don't think I'll have any interested in servicing this amp in the future. Should it ever be necessary out of warranty I'll happily pay someone to save me the hassle.
I can work on the Fuchs without issue (PCB w/ chassis mounted sockets, jacks, pots, and switches - fairly clean layout) and have been allowed to without affecting my warranty (the folks over at Fuchs ROCK!). I have called and talked with Andy or one of the techs regarding a specific tweak and been given the required information to perform them myself without voiding my warranty. Very cool indeed! This is a common thing - tuning / revoicing Dumble ODS type amps to best suit the owner/players technique and preferences. Mine is so dialed in it feels like my brain, my hands, the guitar, and the amp are all hard-wired together. None of this was necessary. The amp was amazing factory stock. I was just curious enough to see what was possible with this amp. A lot so I found out!
The great thing about the Mark V is that there's so much flexibility available from the provided controls that a similar vibe may be dialed in for a vast array of tones. The connection isn't quite as deep as it is with the Fuchs but it's **** close! I wouldn't change a thing about the MkV - perfect execution IMHO!
A friend of mine (maybe) inserted his tube the wrong way and got some loud hum. Apparently, when he was swapping tubes the tube "key" broke off inside the socket and he didn't notice. When he went to put the tube back in, it went right in. The only problem was, the tube was inserted incorrectly which allowed the pins to short. Upon removing the chassis we found a burned resistor. 470k 1watt, if I remember? Anyway, it is a great amp to look at inside and out. The design is very nicely done and the resistor that burned out likely saved the amp from real melt down. Replacing the resistor was easy and all is well. I know the warranty states that you must use Mesa tubes but getting better tubes, preferably RCA, will be a good sound investment. The amp also sounds great with EL34 power tubes. No mixing power tubes please..
Here is a great thread done by another forum member on mixing El34 / 6L6.
http://forum.grailtone.com/viewtopic.php?f=33&t=38013&start=30
Here is a great thread done by another forum member on mixing El34 / 6L6.
http://forum.grailtone.com/viewtopic.php?f=33&t=38013&start=30
shogun said:
True that! I'm playing a pair of Musicman Bongo 4HH basses (one with flats, the other with roundwounds) through a Markbass Jeff Berlin 1x15 combo. The amp sounds like a loud, clean Ampeg B-15N with an amazing degree of sonic flexibility and the basses cover everything vintage and modern with amazing fidelity! The Markbass is a definite keeper.
I just left the warrany service shop with my MkV combo in hand. The issue was an output tube failure. The associated pair was replaced and all is well. I'm on my way home with the amp now and I am very much looking forward to making some noise tonight!
+1
Calm cool collective. Had a runaway tube, chilled and waited for some new tubes and is
back playing an amp he loves the sound of.
Problems with modern day tubes period. It is my opinion that mesa screens their tubes
second to none. Yet, you never know the beating the head takes on the way to the store and
beyond. They test the tubes, match them, burn them in, then hit them with the wooden handle of
a mallet. If they do not short or fail they pass. Yet any tube can fail. Modern tubes regardless of
the make will fail before any tube of the days gone by. i.m.H.o.
Best to you.
Calm cool collective. Had a runaway tube, chilled and waited for some new tubes and is
back playing an amp he loves the sound of.
Problems with modern day tubes period. It is my opinion that mesa screens their tubes
second to none. Yet, you never know the beating the head takes on the way to the store and
beyond. They test the tubes, match them, burn them in, then hit them with the wooden handle of
a mallet. If they do not short or fail they pass. Yet any tube can fail. Modern tubes regardless of
the make will fail before any tube of the days gone by. i.m.H.o.
Best to you.
Glad to hear your amp is ok.....I just picked up a new Mark V head and just LOVE it. IT did come with a faulty pre amp tube...volume was fading sporadically but I changed a few of the suspected culprits and its all good. Brought it to rehearsal and got unsolicited ravings regearding my tone from band members ( who usually could care less about tone )...that alone speaks volumes
Seems like the only issue with these amps is tube reliability....no other gremlins have reared their ugly head as far as I know.
Seems like the only issue with these amps is tube reliability....no other gremlins have reared their ugly head as far as I know.
Since my normal settings across the entire amp were changed while in for service I played around with the various voicings in each channel for a bit when I first fired it up last night. Each of the voicings in the first channel are just outstanding!! Any of these would make for an ideal single channel NMV amp. I had each set up this way last night with various power settings and each sounds amazing! The 'Tweed' voicing is a lot of fun to play through at volume. I messed around with everything for a bit, primarily as a full functional test to be sure everything is functioning properly following its bench time at the service center. Everything sounds great, fantastic tones to be found in each channel and mode. What a great sounding amp!
There's no doubt that a great many issues with tube amps are the tubes themselves or damage caused by faulty output tubes. Switches and relays can fail but, properly rated, these should hold up well for many, many years of regular use. Component failure (properly rated/spec'd caps, resistors, diodes, chokes, transformers) without some outside contributing factor is not nearly as likely to happen. There are also plenty of failures associated with poor build quality - Fender has sold countless tube amps with board mounted plastic jacks and board mounted / supported pots with plastic housings and shafts (not something Mesa owners need worry about). Take the build quality failures out of the equation though and tubes are definitely the leading cause of tube amp failure.
There's no doubt that a great many issues with tube amps are the tubes themselves or damage caused by faulty output tubes. Switches and relays can fail but, properly rated, these should hold up well for many, many years of regular use. Component failure (properly rated/spec'd caps, resistors, diodes, chokes, transformers) without some outside contributing factor is not nearly as likely to happen. There are also plenty of failures associated with poor build quality - Fender has sold countless tube amps with board mounted plastic jacks and board mounted / supported pots with plastic housings and shafts (not something Mesa owners need worry about). Take the build quality failures out of the equation though and tubes are definitely the leading cause of tube amp failure.
Jonathan Vipond
New member
Hi there! First post here...
I've just had the same problem I think. I've had the combo for about 4 weeks but just took delivery of a 4x12 recto cab for when I gig larger venues. I hooked it up at the back as detailed in the instruction manual and it sounded great but when I changed channels this low hum would kick in, though I could still play over the top of it. After switching the amp of and the back on again the hum would go away but every time I changed channel using the footswitch it would return.
So, I tried this with the channel changer on the back and before I had even changed the channel the hum kicked it just when I touched the knob! This knob also seemed a bit dodgey as it would select clean - crunch - OD - CLEAN - footswitch when I turned it through settings. This may have something to do with it but do you think that this sounds like a tube that's gone? My amp is only about a month old and has only been gigged once.
Just spoke to the shop where I got it and they said they'd honor the guarantee as I have a pretty good relationship with them already. Does this sound like it could be something serious?
I've just had the same problem I think. I've had the combo for about 4 weeks but just took delivery of a 4x12 recto cab for when I gig larger venues. I hooked it up at the back as detailed in the instruction manual and it sounded great but when I changed channels this low hum would kick in, though I could still play over the top of it. After switching the amp of and the back on again the hum would go away but every time I changed channel using the footswitch it would return.
So, I tried this with the channel changer on the back and before I had even changed the channel the hum kicked it just when I touched the knob! This knob also seemed a bit dodgey as it would select clean - crunch - OD - CLEAN - footswitch when I turned it through settings. This may have something to do with it but do you think that this sounds like a tube that's gone? My amp is only about a month old and has only been gigged once.
Just spoke to the shop where I got it and they said they'd honor the guarantee as I have a pretty good relationship with them already. Does this sound like it could be something serious?
