Help with revalving? Any advice really appreciated!

[ashevans09]

Righty oh, I've been putting this off but it my Mesa 400+ needs revalving. Unfortunately, I know pretty much diddly squat about valves - I can name different types like 6550s and 12AX7s and what not and have an appreciation of whether they live in the pre or power section but beyond that I'm pretty lost in all honesty.

I've looked at the Watford website since it has such a good rep here and I've found that they have three Mesa 400+ sets available. Any advice on which one to get? Or indeed should I go somewhere else?

http://www.watfordvalves.com/products.asp?id=32&man=261

I tend to run active basses (primarily my P/MM sandberg) and EQ with reasonably high bass, higher mids and lower treble. Gets a nice punchy sound with my basses which I like, also like a bit of gain in there to give it some bite. I've found for my band that works and punches nicely through two guitars, has a lot of presence and drives the band. Would the standard set be what I'm looking for? Or would I be better off with the retro set? Don't mean to sound overwrought about this, it's just it's a lot of money to drop on something and I just don't want to make the wrong choice!

Thanks for any help you guys can offer,

Cheers,

Ash

[voxpop]

I would ring Watford valves they will advise you.
They are there to help you choose the right set.

[Mr. Foxen]

Firstly, how have you established that the amp needs fully revalving?

[ashevans09]

[quote name='Mr. Foxen' timestamp='1355401036' post='1897832']
Firstly, how have you established that the amp needs fully revalving?
[/quote]

I was getting some crackling and noise a few months ago, and wanted to try and sort it before going on tour. Took it to a tech (recommended by Mansons so assume he's reasonably decent), who managed to get rid of the problem to an extent but recommended a full revalve sometime reasonably soon. It's been getting progressively noisier so I figured it was time? Very happy to be wrong on this!

[Mr. Foxen]

[quote name='ashevans09' timestamp='1355433178' post='1898460']
I was getting some crackling and noise a few months ago, and wanted to try and sort it before going on tour. Took it to a tech (recommended by Mansons so assume he's reasonably decent), who managed to get rid of the problem to an extent but recommended a full revalve sometime reasonably soon. It's been getting progressively noisier so I figured it was time? Very happy to be wrong on this!
[/quote]

Anyone suggesting a full revalve without having tested all the valves is a bit dodge. And if all the valves are not working, it will sound very wrong not just a bit. Because of the way the power section in a Mesa is made, there is a certain extent to which replacing all the power amp valves at once might be necessary, but really, the technically correct advice there is to get a properly made amp rather than chuck tons of money at a bad one that will only fix the issue short term. Might only be one noisy pre valve making the issue. Might even be filter caps, they might be getting about that age now.

[ashevans09]

[quote name='Mr. Foxen' timestamp='1355433419' post='1898465']
Anyone suggesting a full revalve without having tested all the valves is a bit dodge. And if all the valves are not working, it will sound very wrong not just a bit. Because of the way the power section in a Mesa is made, there is a certain extent to which replacing all the power amp valves at once might be necessary, but really, the technically correct advice there is to get a properly made amp rather than chuck tons of money at a bad one that will only fix the issue short term. Might only be one noisy pre valve making the issue. Might even be filter caps, they might be getting about that age now.
[/quote]

Hmm, a lot to think about there. He seemed to know his chops and was recommended by a decent source... second opinion from someone else a decent road to go down?

[ashevans09]

(thanks for all the information so far btw )

[Mr. Foxen]

Easy way is get some pre valves first and try them. I have a valve tester, so I'd run all the power ones through that, bad ones should show up there. If those are fine, bangs tend to be cracked solder and dirty sockets, and hum tends to be bad caps. Old valves is weak sound and weird distortion (which cab also be caps), sometimes valves arc internally, but you can see that sometimes and it comes up on testing as intermittent failures (like you ding them in the tester and see if the light blinks).

[4 Strings]

Not had many valve amps but I understood valves last for years and years.

[Big_Stu]

[quote name='4 Strings' timestamp='1355530511' post='1899780']
Not had many valve amps but I understood valves last for years and years.[/quote]

I'm told - by professional experts - that that is the case, but you would have to have them tested properly if you don't know their history. My amp had what turned out to be virtually new KT88s in it, they hadn't been used for 18 years, but were still as was when tested.

[quote name='voxpop' timestamp='1355383647' post='1897538']
I would ring Watford valves they will advise you.
They are there to help you choose the right set.
[/quote]

+1, I've had reliability concerns about valves available which were raised on here (JJ KT88s as it goes) & options available, all of which were stocked by Watford & I've recently received a very helpful email from "Derek" there.
He has given open opinions about some issues & given advice about which valves to go for - which weren't the most expensive they had.

Have you checked the "Recommended Amp Techs" thread in the Repairs area?

[4 Strings]

In the end I think the OP is right to get a second opinion on here, the advice 'to replace all the valves' may be sound but it doesn't seem to be based on anything and appears a little glib. You could just as easily advise to start replacing all components from the left to the right until the problem is solved.

[umph]

[quote name='4 Strings' timestamp='1355563220' post='1899891']
In the end I think the OP is right to get a second opinion on here, the advice 'to replace all the valves' may be sound but it doesn't seem to be based on anything and appears a little glib. You could just as easily advise to start replacing all components from the left to the right until the problem is solved.
[/quote]

Hes probabaly tested the amp and found that it's not doing the power because alot of the valves are down on emmision. A full revalve on a 400+ is expensive so I'd probably do the same and recommend it needs doing when they can afford it to the customer

[ashevans09]

[quote name='Mr. Foxen' timestamp='1355434583' post='1898488']
Easy way is get some pre valves first and try them. I have a valve tester, so I'd run all the power ones through that, bad ones should show up there. If those are fine, bangs tend to be cracked solder and dirty sockets, and hum tends to be bad caps. Old valves is weak sound and weird distortion (which cab also be caps), sometimes valves arc internally, but you can see that sometimes and it comes up on testing as intermittent failures (like you ding them in the tester and see if the light blinks).
[/quote]

Sorry to be so technically inept but what are prevalves? I really do appreciate all the advice though . In all honesty it has been sounding weaker as of late. I really can't remember very well but when the guy did service it he did replace some components, I just can't for the life of me remember what. I want to say it was some caps but since it's been mentioned I can't really differentiate if it's only ringing a bell because you've mentioned it, if you get what I mean?

[quote name='4 Strings' timestamp='1355530511' post='1899780']
Not had many valve amps but I understood valves last for years and years.
[/quote]

Me too, thing is though I've never revalved it in the time I've had it and I couldn't tell you when it had been revalved before I owned it!

[quote name='Big_Stu' timestamp='1355531301' post='1899784']
+1, I've had reliability concerns about valves available which were raised on here (JJ KT88s as it goes) & options available, all of which were stocked by Watford & I've recently received a very helpful email from "Derek" there.
He has given open opinions about some issues & given advice about which valves to go for - which weren't the most expensive they had.

Have you checked the "Recommended Amp Techs" thread in the Repairs area?
[/quote]

That's a good shout actually, I'll have a lookse there for a tech near me . Thanks! And Watford sound like a good call then, if I do go ahead with the revalve I'll go with them .

[quote name='4 Strings' timestamp='1355563220' post='1899891']
In the end I think the OP is right to get a second opinion on here, the advice 'to replace all the valves' may be sound but it doesn't seem to be based on anything and appears a little glib. You could just as easily advise to start replacing all components from the left to the right until the problem is solved.
[/quote]

Second opinion it is , I'll be honest he did replace components and did some testing, Really sorry to say I can't be more specific as he was one of these people who spends their lives surrounded by the things (his house was literally stuffed full of amps, it was insane) and was giving a lot of tech speak about what he did with it that I didn't fully understand.

Once again, thank you all for taking the time to respond

[Mr. Foxen]

[quote name='ashevans09' timestamp='1355604736' post='1900579']
Sorry to be so technically inept but what are prevalves?
[/quote]

Preamp valves, small ones that work the knobs and such. They are also cheap and don't need matching, plug and play, so if one of those is dying and making for a weak sound, its an easy fix.

[Ancient Mariner]

You mentioned 12AX7s in the original post - those are preamp valves.

As for valves lasting years, this depends on many factors including how hard they've been worked. If the amp has been driven hard and loud a lot then the power valves (those 6550s mentioned in the OP too) will wear, but if it's been put away then the valves will normally be fine, even if they're 50 years old. Preamp valves don't usually wear like power valves, but they do sometimes become loose inside and go microphonic.

[ashevans09]

[quote name='Mr. Foxen' timestamp='1355604944' post='1900585']
Preamp valves, small ones that work the knobs and such. They are also cheap and don't need matching, plug and play, so if one of those is dying and making for a weak sound, its an easy fix.
[/quote]

Ah right getcha, hadn't heard them referred to as that before. Sounds like a good start

[quote name='Ancient Mariner' timestamp='1355607835' post='1900622']
You mentioned 12AX7s in the original post - those are preamp valves.

As for valves lasting years, this depends on many factors including how hard they've been worked. If the amp has been driven hard and loud a lot then the power valves (those 6550s mentioned in the OP too) will wear, but if it's been put away then the valves will normally be fine, even if they're 50 years old. Preamp valves don't usually wear like power valves, but they do sometimes become loose inside and go microphonic.
[/quote]

In terms of work, what constitutes being worked hard? The head's been toured, gigged loads at high volume and practiced through regularly in the 4 or so years I've had it? Probably done similar before it came into my ownership.

Thanks again guys, I'll get started on it . Heading off to work now, see ya!

[Mr. Foxen]

I've come across a lot of dud preamp valves.

[VTypeV4]

12 x 6L6 are mighty damn pricy! It's one of the reasons I've never had a 400+ although I'd certainly have it's smaller cousin, a buster head.

I'd explore all other avenues before making the plunge. All the advice on here has been great so far.

[4 Strings]

With my O Level Physics so far in the past, this helped with understanding what a valve does.

http://www.youtube.com/watch?v=UM3av6moJd4