Mesa 400+ issues

[woodyratm]

Hey guys,
Wonder if someone could assist me? As i mentioned the other day in my band thread, my 400+ died just before recording.

I have no idea what the problem is.

I set everything up as normal, switched the amp on - with stand by still on - so the tubes were warming up.
When i was away to test everything was working, flicked the standby off and i got this buzzing sound, but VERY quietly i could hear the bass notes.

We tried a different bass, different cable, differnet cable to the cab but it still kept doing the same?

Anyone have any ideas what it could be?

A few of my mates with 400+ (well 2 of them!) had their mesa's crap out when needed too, even more annoying is the fact that it worked amazingly at practice 2 days before hand, and every other practice before that!

Cheers for any suggestions.

Davie

PS - I checked the fuse and it was fine, I haven't had a chance to even look at the valves neither..

[Mr. Foxen]

If all the power tubes are fine, maybe a dead pre one? Easy fix if so.

[woodyratm]

Anyway of telling how it's dead?

Cheers

[Mr. Foxen]

[quote name='woodyratm' post='923563' date='Aug 13 2010, 10:16 AM']Anyway of telling how it's dead?

Cheers[/quote]

Swap them for other ones. Think there is something other than a 12ax7 in the mesa pre, so look out for that.

[ped]

I had this issue once with one of mine but I switched it all off and on again and it was fine ever since!!

[umph]

sounds like a preamp valve has gone, try turning it off and on again to see if it cuures it. If it does tap them all while its on to see which one goes into oscillation

[Beedster]

[quote name='ped' post='924765' date='Aug 14 2010, 11:13 AM']I had this issue once with one of mine but I switched it all off and on again and it was fine ever since!![/quote]

Three years of studying Electronic Music Technology and the most useful thing I learned was that the best way of fixing an amp was to turn it off and turn it back on again. It probably explains why IT Help Desk staff ask you to do the same thing

[woodyratm]

Cheers for the reply folks. Will try your suggestions later.
It hasnt been switched on again for 2/3 weeks so fingers crossed the ol' off n on again works!

[Beedster]

[quote name='umph' post='924780' date='Aug 14 2010, 11:31 AM']... tap them all while its on to see which one goes into oscillation[/quote]

Very carefully.

[woodyratm]

[quote name='umph' post='924780' date='Aug 14 2010, 11:31 AM']sounds like a preamp valve has gone, try turning it off and on again to see if it cuures it. If it does tap them all while its on to see which one goes into oscillation[/quote]

Opened her up to check the valves - all the power valves are lighting up fine - tried tapping the pre valves but they didn't appear to move at all..


[quote name='Beedster' post='924798' date='Aug 14 2010, 11:47 AM']Three years of studying Electronic Music Technology and the most useful thing I learned was that the best way of fixing an amp was to turn it off and turn it back on again. It probably explains why IT Help Desk staff ask you to do the same thing [/quote]

Tried this too - I'm getting more volume than before but still has to be cranked to get "normal" bedroom volume (eg channel volume full and the master volume volume at like 5/6)

Does this sound like something dodgy with a preamp valve or power one? I don't have any spare valves right now to test neither.

Cheers guys for all the help - Love this amp to bits, but kinda freak out it's gonna die at any moment (what with being discontinued etc)

[woodyratm]

Also I can take pictures if required? just let me know

[AttitudeCastle]

I can't help in anyway as i don't know anything about an amps guts, especially a valve one!

BUT when you get it sorted, at your next gig around the 'deen can i try it out?

Cheeky

[woodyratm]

Sure. It may also be for sale soon tempted by a svt vr!

[AttitudeCastle]

[quote name='woodyratm' post='925450' date='Aug 15 2010, 11:30 AM']Sure. It may also be for sale soon tempted by a svt vr![/quote]

Unless i can have it for a bowl of peanuts and a fiver, don't think i can afford it! haha,

Ummmm if you get an SVT VR can i try that too? haha! Your welcome to try my gear when i get some stuff worth usuing haha!

[woodyratm]

[quote name='AttitudeCastle' post='925488' date='Aug 15 2010, 12:00 PM']Unless i can have it for a bowl of peanuts and a fiver, don't think i can afford it! haha,

Ummmm if you get an SVT VR can i try that too? haha! Your welcome to try my gear when i get some stuff worth usuing haha![/quote]

Sure - Don't see why not.

Does anyone know of any local (scotland) and reasonable amp techs?

Need this fixed!

[thebassman]

[quote name='woodyratm' post='926178' date='Aug 16 2010, 09:41 AM']Sure - Don't see why not.

Does anyone know of any local (scotland) and reasonable amp techs?

Need this fixed![/quote]

Has anyone been messing with the effects loop control, inside at the back.
When I first got mine I had a similar problem. Try Turning it down to zero.

[woodyratm]

Still buzzing loudly
Got really hopefull there, it was on 6.

Cheers anyway

[Steff]

I can share my experience with the Mesa I bought 3 days ago, it has similar problem. At a rehearsal yesterday after playing for an hour, I thought it started being quieter, but then I thought it's just my ears. Then I heard funny cracking noises through the cab and I saw a miniature lightning storm from the back ... It was still running though... There was no smoke or smell though. I couldn't really see where the blue lightning comes from. So I went home and opened it. Checked the sockets for loose connections or signs of burning, but there were none. I've pulled out the valve that I thought I saw blue sparking earlier and first knocked it with my finger, and it was making this clinking noise. At closer inspection I saw little white particles inside, like burnt at a high temperature metal. So I guess it's just that valve has gone bad, already ordered two and will replace them as soon as I get them. You might wanna do the same - take the valves out and check them by gently knocking them with a finger or a pencil, there shouldn't be any "ringing" sound and take a close look at the inside, if you see any loose particles - that's a good sign a valve's gone bad. And the one that was bad on mine, was still "working", if I didn't suspect the sparks have come from that one, I couldn't tell there's something wrong.

Sorry for my English and I hope that helps.

[woodyratm]

Cheers for this - I'll give it a go tonight.

Is there anything i should lookout for when touching the valves? Eg are they like car lights - you're not meant to touch the glass part?

[Steff]

Hmm... As far as I know, there's no harm of touching the glass. Will check that later with a friend of mine, who's a valve maniac. Be careful when pulling out, because they're usually fit tight in the socket. Don't try to pull it straight up, better combine pulling with gentle left-right moves, and watch not to bump the valve into another one or an edge when it finally comes out.



Just had a word with my tech friend - no harm touching the glass part.

Edited August 18, 2010 by Steff

[woodyratm]

[quote name='Steff' post='928363' date='Aug 18 2010, 09:13 AM']Hmm... As far as I know, there's no harm of touching the glass. Will check that later with a friend of mine, who's a valve maniac. Be careful when pulling out, because they're usually fit tight in the socket. Don't try to pull it straight up, better combine pulling with gentle left-right moves, and watch not to bump the valve into another one or an edge when it finally comes out.[/quote]


Theres a joke in there somewhere...

Sorry. Cheers for the help - I'll give this ago tonight! Fingers crossed!

[Steff]

No joke mate... It's just my crappy English that makes it looks confusing. Sorry about that .

[woodyratm]

[quote name='Steff' post='928373' date='Aug 18 2010, 09:28 AM'] No joke mate... It's just my crappy English that makes it looks confusing. Sorry about that .[/quote]


Nah - nothing about the language

Thanks alot for the help

[CHRISDABASS]

I always thought touching the glass part and not cleaning ur grubby finger prints off afterwards could lead to hot spots on the glass?? I could sooo easily be wrong though

[Steff]

Well putting it that way you might be right, I never thought about it, because I always clean them after installing, I hate to see fingerprints on a clean shiny valve...