Mark III Dead. what to do now?!

[Mellowtronic]

Hey all,

So Ive had my Mark III Blue stripe for a few weeks now and it has been in my former bands practice spot. They haven't used it much, nor have I.

Now the guy I purchased it from said it just came back from Mesa, where it was serviced and given a clean bill of health by Mike B.

Having played it myself, there seemed to be no issues.It could be cranked, it could whisper and all else between. No problems. Tubes sounded good and everything worked as it should.

Fast forward to this weekend. They took it to a recording session and gave it back to me. I plug in in today and NOTHING.

Not a single note, cough, fart, nothing. I figured there was a knob turned down, effects send issue, nothing... All tubes are fit snugly into place. everything is where it should be. Nothing. All I can hear now is a hum, yes, just a hum coming from inside the chassis, not through the speaker. That worries me like all hell. I figure something is wrong inside because usually a natural hum from the output will get louder as I turn up the master. This does not. It's definitely something wrong in the amp.

I've tried trouble shooting with new cables, new guitar, nothing again. Hum continues, in either class A or simul class. I cannot for the life of me figure out the issue.

I suspect they blew something, perhaps by unplugging the internal speaker and leaving the amp on. They're not complete idiots, but I've seen them do silly things with amps before. Any ideas before I take it to my tech?

 

[acorkos]

are all the tubes intact and seated completely in their sockets? make sure your speaker cable plugged in completely, verify that the cable is working, and that your speaker works, too. you might need to plug a different amp into your cab/cable to verify. rule out a missing tube or bad speaker or speaker cable before you assume your output tranny is toast.

 

[Mellowtronic]

All tubes are in place and sitting pretty. That was the first thing I checked out, as I've had tubes wiggle loose during transport on previous amps. I actually checked all sockets, such as input, speaker outs by pushing in a plug and pulling out a plug. I have not been able to check speaker as its my only amp and it is the internal Ev inside, but I will try somehow. I find it hard to believe that from the end of the session Saturday when it was working, and today it was damaged, but def worth trying eh.

if the out put tranny is toast, what do you expect a base price for repair to be?

 

[MrMarkIII]

It's my experience that toasted trannies give bad smells and blown fuses. It's probably the speaker, but I've never blown a Mesa tranny or an EVM. Way over-engineered, almost idiot-proof.
Got manual?
I quote:
"V1, as we said, is usually the
culprit for general noise problem , especially when both Rhythm and Lead Modes are affected, or if the amp is dead. V2 can also be
the culprit for dead amps. If you plug your guitar into the Effects Return Jack and it produces sound - which it should - then chances are
your power tubes and output driver (V5) are OK and V1 or V2 is at fault. V3 contains the Lead Mode circuitry so if the problem seems
limited to the Lead, Change V3. (High settings of the Lead knobs also require a good quality V1.) V4 is the Reverb tube. Change it if
you have a reverb problem. But first check that the reverb cables are plugged in securely. Grey cable goes in the socket toward the
front of the amp. V5 is the socket which is set back mid-way to the output tubes. It can be the culprit if the amp is dead, has low gain or
lacks boldness, warmth and/or clarity.
If you are in doubt, you should merely replace the preamp tubes one-at-a-time beginning with V1. If the replacement tube fails to cure
the problem, put the original tube back into its socket and go on to the next. Don't mix up the tubes and don't bother testing them on a
drug-store tester. Only the substitution method works for sure. We advise removing a power tube or two to help gain access to the central preamp tubes."

"When removing a power tube, first bend the retaining ring out of the way. Then GENTLY rock the tube back and forth slightly, while
pulling down. If you rock it too far, you will break off the plastic key on the tube base. This is not something we cover under warranty. If
you're reasonably careful, you won't break it. If it does break off, you can still use the tube as long as it's oriented properly in the socket.
Look carefully at the bottom of the tube and you'll probably see the outline of the plastic key. This should line up with the notch in the
center hole of the tube socket. Also look for the scratches in the plastic base caused by the retaining ring. When you think you've got it
right, make sure the amp is on Standby, then turn on the Power. If the tube filament lights, up, then you've got it right and everything is
OK. If the tube doesn't light up, turn off the power and try again to get the tube plugged in properly. A broken plastic key does not hurt
the working of the tube, it just means it can be plugged in seven wrong ways and one right way. By double checking the filament -- with
the amp on Standby -- you can be absolutely certain that everything is OK without any risk of damaging your amplifier."

 

[Mellowtronic]

Will try all of that tonight! We shall see! I've never had a V1 tube die suddenly on me, but hey, anything is possible.

 

[acorkos]

check the speaker cable connections at the speaker, too.

 

[Bonez]

Does your amp have a speaker mute or silent recording out switch like my dc-5 does ? if so it could have been accidentally switched on muting everything during transport.

 

[trey85stang]

Will try all of that tonight! We shall see! I've never had a V1 tube die suddenly on me, but hey, anything is possible.

very possible, start with v1 then check v5. Those two can cause no output at all.

99% chance it is a bad tube.

 

[kaluablue]

Check the fuse first.
Does the pilot light glow?
If not, check power cable.
If yes, check the fuse.
If a preamp tube was bad, you would still hear a little hiss through the speaker from the power amp.
If the amp is dead silent, pilot light is on and fuse is ok, try a different speaker.
You can check the speaker itself by unpluging it and holding the plug against a 9V battery. It should should 'pop' then (this will not damage the speaker)

If all this doesn't help, call a tech.

 

[Mellowtronic]

Sucess! Plugging into the effects return gives me output, so the culprit is likley a bad preamp tube! Yes?

Orderding up some new tubes today. As recommendations? Go with the standard Doug's tube combo for Marks?

 

[goodwill559]

Depends on which tube is bad, but I suggest getting a Mullard with mc1, f91, or f92 production code, and a Raytheon long black plate, to be used in V1 & V3. I have the Mullard in V1 and the Raytheon in V3 and I just love the sounds of the lead channel.

 

[phyrexia]

hey, make sure it's not just that the amp thinks something's plugged into the FX send - that happens to me from time to time because I've never cleaned the jacks - take a patch cable and go from FX Send to FX return.

Otherwise it'll be V1-3.