NAD Ruined....Already need a Diagnosis.

Alnico

Ah,..................Sheffield is about a 4 hour drive on a Sunday. Ok, maybe best not to but if you need these valves, let me know and i'll send them up.

Sounds like you've got a plan now but still not nice having a New Amp do this, especially at the weekend.

Hope it gets sorted soon man.

Bellycaster

Thanks @Alnico

I very much would like to be more hands on with stuff and will seek to overcome my technofear, haha, like everyone says, it's probably a piece of piss. Just as an extra question, I thought that when a tube is replaced it needs biasing or something.

Not sure about the 5;50, but "Biasing" is a very familiar term that I keep hearing.

Alnico

@Bellycaster

I have no idea what goes on in an amplifier, but i'm an ex motorbike mechanic so taking stuff apart and putting back together again with nuts, bolts and screws doesn't phase me (No pun intended).

You may be right about biasing, i have no idea.

strtdv

@Bellycaster, preamp valves (ie 12ax7/ecc83, they're the same thing) don't need biasing, it's just the power amp valves (el84, el34, 6L6, 6v6 etc) that need it.
Preamp valves can just be changed, no adjustment necessary

Bellycaster

Ahhh, didn't know that, all helpful info, thanks @strtdv

english_bob

If you'd feel any more confident changing the tubes with clear instructions in your hand have a look at the manual. Most Mesa manuals have a tube chart in the back that shows which of the many tubes in the back is which, and also a guide to diagnosing and fixing simple faults. As long as you're careful, the power is off and you don't start taking the amp apart (no need anyway) there isn't much to mess up.

ICBM

strtdv said:

@Bellycaster, preamp valves (ie 12ax7/ecc83, they're the same thing) don't need biasing, it's just the power amp valves (el84, el34, 6L6, 6v6 etc) that need it.
Preamp valves can just be changed, no adjustment necessary

Mesa amps are purposely designed to not need biasing even when you change power valves, as long as you stick to either their own branded valves, or ones from other sellers which are within the same performance range. They don't actually have a bias adjustment control.

crunchman

Even if this goes back and is fixed by the distributor, it's worth getting some spare valves for it.  Valves do go - normally at awkward times.

Jalapeno

Thought Mesa Boogies didn't need biasing ....

I agree about using Mesa branded valves - a tech put JJs in my Nomad and it changed the character completely (and not in a good way).

ICBM

Jalapeno said:

Thought Mesa Boogies didn't need biasing ....

I agree about using Mesa branded valves - a tech put JJs in my Nomad and it changed the character completely (and not in a good way).

Mesa are using JJs now. I really don't like them either - their power valves are OK but their preamp valves sound awful (in my opinion).

I'm not a fan of Sovteks either, which they used before - I much prefer the standard Chinese ones they used in the 90s, although the power valves weren't very reliable.

Bellycaster

Thanks again Lads.

@ICBM

I was meaning to ask about the warnings you hear about residual charge left in Amplifiers. ie: Parts on the inside of Amps holding a charge even when unplugged. This most likely does not apply to the tubes, but I thought I'd ask.

Your right about the Mesa being fixed bias too.

@english_bob

That's another thing that put me off, the fact the tubes hang down instead of sticking up, probably the most likely layout on a combo, but that makes it more awkward to swap tubes I guess, if you don't take the chassis out.

The Bogner Head I have looks very easily accessible, the Mesa, not as easy for access even with the guard off and your working upside down so to speak (with the amp in one piece).

:-)

strtdv

You can turn the amp upside down surely?

Valves don't hold charge, but they do get hot, so leave them to cool down before swapping them (unless you enjoy the smell of your own skin burning)

Bellycaster

strtdv said:

You can turn the amp upside down surely?

Valves don't hold charge, but they do get hot, so leave them to cool down before swapping them (unless you enjoy the smell of your own skin burning)

Could turn the amp upside down I suppose, I was probably worried that might be unwise, I worry too much. Have watched some vids though of when the tech removes the Chassis and flips it over so they have all the space in the world to work on it.

I'm aware the tubes get hot, that much I know at least.

:-)

english_bob

Bellycaster said:

 

@english_bob

That's another thing that put me off, the fact the tubes hang down instead of sticking up, probably the most likely layout on a combo, but that makes it more awkward to swap tubes I guess, if you don't take the chassis out.

 

Not really. It's one of many factors that might make it a little more fiddly on some amps than others, but like @strtdv says, you can always flip the amp upside down, or on its side if it helps you to get at the valves.

I find that the amount of room around the valve you're working on is the thing that makes most difference- if it's sandwiched between two other valves and there's only an inch or two of clearance between the top of the valve and the cabinet to get your hand in to (which is more likely in a head than a combo) you'll have a harder time unseating the valve. I find that a gentle side-to-side or circular motion is good- don't just grab hold and pull directly away from the base.

As far as I'm aware it's only capacitors that can hold charge when the amp is off, and then only the big ones that will give you a jolt. Either way, you won't come anywhere near one if you leave the amp in one piece. Valves only hold heat, so let them cool or wrap a cloth around them before you handle them.

english_bob

Bellycaster said:

Could turn the amp upside down I suppose, I was probably worried that might be unwise, I worry too much. Have watched some vids though of when the tech removes the Chassis and flips it over so they have all the space in the world to work on it.

 

Only really necessary when you need to work on parts that would ordinarily be inside the amp and inaccessible when it's assembled. An amp chassis is heavy and often much heavier at one end than the other, which makes it awkward to handle, so removing one and putting it back again can be a bit of a ball-ache in itself.

BloodEagle

I mean this is the nicest way, but further down the line you will get other valves going - thats the nature of valve amps - if if you arent willing to change just 1 simple preamp valve then maybe the world valve amps isnt for you

english_bob

BloodEagle said:

I mean this is the nicest way, but further down the line you will get other valves going - thats the nature of valve amps - if if you arent willing to change just 1 simple preamp valve then maybe the world valve amps isnt for you

1. Ouch.

2. True.

Bellycaster

Thanks for the info @english_bob

@BloodEagle

I actually do intend to have a go myself in the future, I know it's an advantage, just on this occasion with it being a new amp, I decided to let someone else look it over. I might not show the confidence on this thread, but the thread(and a couple of PM's) are providing some knowledge that will help in the future.

Just a case of building up the attitude that "I can do it myself" and that will come. If my Bogner has a similar failure in the near future, I'll take the plunge then.

As for gigs, a back up solid state amp is usually part of my plans. I've enjoyed tube amps for the last 2 years, there is always a way round things even if I don't work on my own amps.but like I say, it's something I know I should learn.