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 Post subject: Re: Valve tolerances.
PostPosted: Mon Feb 15, 2016 1:20 pm 
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Mark IV
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EL34s will run beyond max dissipation in full power - they should be used in Variac mode only.

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 Post subject: Re: Valve tolerances.
PostPosted: Mon Feb 15, 2016 1:42 pm 
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Mark III

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Authorized Boogie wrote:
EL34s will run beyond max dissipation in full power - they should be used in Variac mode only.


Really? Doesn't mention that in the manual? only says to make sure the bias switch matches the tubes in use?

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 Post subject: Re: Valve tolerances.
PostPosted: Mon Feb 15, 2016 6:52 pm 
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Mark IV
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Wayno wrote:
Authorized Boogie wrote:
EL34s will run beyond max dissipation in full power - they should be used in Variac mode only.


Really? Doesn't mention that in the manual? only says to make sure the bias switch matches the tubes in use?


It could be clearer and more definitive, but it is indeed in the manual, recommended on page 43 to use Variac when using EL34's. Thanks!

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 Post subject: Re: Valve tolerances.
PostPosted: Tue Feb 16, 2016 3:55 am 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
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Authorized Boogie wrote:
Wayno wrote:
Authorized Boogie wrote:
EL34s will run beyond max dissipation in full power - they should be used in Variac mode only.


Really? Doesn't mention that in the manual? only says to make sure the bias switch matches the tubes in use?


It could be clearer and more definitive, but it is indeed in the manual, recommended on page 43 to use Variac when using EL34's. Thanks!



Many thanks, must have missed that part! Thank you for clearing that up.

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 Post subject: Re: Valve tolerances.
PostPosted: Thu Feb 18, 2016 8:21 am 
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Mark III

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Certainly enlightening as to why I can't get on with Simul-Class. Preferring either class A or A/B.

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 Post subject: Re: Valve tolerances.
PostPosted: Thu Feb 18, 2016 1:50 pm 
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Mark III

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Funny how a certain setting can make or break a tone for an individual. Never know how specific an opinion could be until i got the boogie 8)

Did you try any EL34's? If so what you reckon?

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 Post subject: Re: Valve tolerances.
PostPosted: Thu Feb 18, 2016 4:13 pm 
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Mark III

Joined: Sat Apr 25, 2015 1:22 am
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Location: MO
Authorized Boogie wrote:
Wayno wrote:
Authorized Boogie wrote:
EL34s will run beyond max dissipation in full power - they should be used in Variac mode only.


Really? Doesn't mention that in the manual? only says to make sure the bias switch matches the tubes in use?


It could be clearer and more definitive, but it is indeed in the manual, recommended on page 43 to use Variac when using EL34's. Thanks!

This information is news to me too. I've read the manual many times and I've never read anything close to that. So I had to go to page 43 and investigate:

NOTE: Using the AC POWER switch set to VARIAC POWER will reduce the strain on EL34 tubes (and 6L6 as well). If you prefer the sound of this setting, you will reduce the likelihood of tube problems and greatly extend their toneful life, as they are basically coasting.

This is what I assume Authorized Boogie is talking about. But this does not say to use el34s in variac mode, it doesn't even recommend it. By Authorized Boogies logic, you should run 6l6s in variac too, because they're mentioned here with el34s.

I've never had a problem running my el34s in full power. And the manual does not, in any way, say that I shouldn't run them in full power.

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 Post subject: Re: Valve tolerances.
PostPosted: Thu Feb 18, 2016 4:50 pm 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
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It could be clearer and more definitive, but it is indeed in the manual, recommended on page 43 to use Variac when using EL34's. Thanks![/quote]
This information is news to me too. I've read the manual many times and I've never read anything close to that. So I had to go to page 43 and investigate:

NOTE: Using the AC POWER switch set to VARIAC POWER will reduce the strain on EL34 tubes (and 6L6 as well). If you prefer the sound of this setting, you will reduce the likelihood of tube problems and greatly extend their toneful life, as they are basically coasting.

This is what I assume Authorized Boogie is talking about. But this does not say to use el34s in variac mode, it doesn't even recommend it. By Authorized Boogies logic, you should run 6l6s in variac too, because they're mentioned here with el34s.

I've never had a problem running my el34s in full power. And the manual does not, in any way, say that I shouldn't run them in full power.[/quote]


Thats how i'd always read it and interpreted it too.

As Authorised Boogie said it's not particularly clear in the manual and it should be re-written really to remove any confusion as the general feeling i'm getting from some of the posts in this thread indicate that EL34's run very hot in the Mark V and it should always be run in Variac mode to protect against damage. Glad i found that out before i ran into problems as i would think repairs to the Mark V can run very expensive!

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 Post subject: Re: Valve tolerances.
PostPosted: Thu Feb 18, 2016 7:44 pm 
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Scroll down this page until use see the pictures of the Bias-Rite meter. The readings were done in Full Power mode. I can see why MESA would suggest Variac mode for EL-34 power tubes, based on the 53mA reading of the inner sockets.

viewtopic.php?f=33&t=38013&start=30

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 Post subject: Re: Valve tolerances.
PostPosted: Fri Feb 19, 2016 3:12 pm 
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Mark III

Joined: Sun Sep 27, 2015 2:50 pm
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JOEY B. wrote:
Scroll down this page until use see the pictures of the Bias-Rite meter. The readings were done in Full Power mode. I can see why MESA would suggest Variac mode for EL-34 power tubes, based on the 53mA reading of the inner sockets.

viewtopic.php?f=33&t=38013&start=30



That was an interesting thread, just read through it and there's a lot of information there.

Really starting to think that the manual could do with e re-write though as it looks like, so far as my limited knowledge and understanding can deduce, that EL34's really need to be run in Variac mode as Full Power seems to be far to hot to be considered safe for the amp. Also, the fact that it doesn't seem to be common knowledge should be addressed really, especially if it prevents a lot of Mark V's running El34's from going into meltdown.

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 Post subject: Re: Valve tolerances.
PostPosted: Sat Feb 20, 2016 1:00 pm 
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Mark III

Joined: Tue Dec 22, 2015 12:15 pm
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Joey any idea what your plate voltages are?
Taking a reading of say 53ma with no plate voltage is only answering half the problem. 53ma at 470v for instance would be fine for class A. Biassed at 100%. So as long as the plate voltage is near 470v, I don't see a problem with that. The outer sockets at 43ma @470v comes in at 80% which is a shade warm. Nothing unusable though.

Be interesting to know as reference. I'll be measuring mine tomorrow.
I also use a 4 socket bias meter, not Weber.

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 Post subject: Re: Valve tolerances.
PostPosted: Sat Feb 20, 2016 1:08 pm 
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Mark III

Joined: Tue Dec 22, 2015 12:15 pm
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Sorry, just saw your plate reading of 450v, which makes things better still. The class A/B sockets are a shade over 75%

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 Post subject: Re: Valve tolerances.
PostPosted: Sat Feb 20, 2016 9:33 pm 
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Dual Recto

Joined: Tue Feb 07, 2006 11:21 pm
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Nicklotsaguitars wrote:
Sorry, just saw your plate reading of 450v, which makes things better still. The class A/B sockets are a shade over 75%


The inner sockets are not reallly Class A untill you go to 10 watt mode. Here is a great page to calculate tube bias.


http://www.tedweber.com/bias-calc

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 Post subject: Re: Valve tolerances.
PostPosted: Mon Feb 22, 2016 2:58 am 
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Mark III

Joined: Sat Apr 25, 2015 1:22 am
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Thanks for linking that thread Joey. Very interesting. You got me wondering now. I've always been on the fence about mixing el34s and 6l6s. I know the manual says no but I saw that you were doing it back at the time of that thread. So I was wondering, did you ever have any problems, of any kind, from mixing the different tube types? I might experiment with mixing if I know someone else never had any problems. And that thread was years ago so if anything was going to go wrong it would have by now. Thanks.

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 Post subject: Re: Valve tolerances.
PostPosted: Tue Feb 23, 2016 5:21 am 
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Dual Recto

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SamuelJ86 wrote:
Thanks for linking that thread Joey. Very interesting. You got me wondering now. I've always been on the fence about mixing el34s and 6l6s. I know the manual says no but I saw that you were doing it back at the time of that thread. So I was wondering, did you ever have any problems, of any kind, from mixing the different tube types? I might experiment with mixing if I know someone else never had any problems. And that thread was years ago so if anything was going to go wrong it would have by now. Thanks.


The amp was not played with the "grey" color code STR 450's. When I saw those inner socket numbers, I shut it down. I believe that the Groove Tubes were used for a while, they were on the ragged edge of safety. Ultimately he (lesterpaul) went back to 6L6's for the better clean sounds. No problems with the amp, though.

As far as mixing goes, the 6L6 bias point is so far off from what the EL-34 tube needs, I wouldn't even bother with it. Funny how opinions change with time. :lol:

Even the "red" color coded MESA tubes will be too hot for the inner sockets in Full Power mode.

Unless you have a bias meter, stick with MESA tubes, and Variac mode with EL-34's, just to be safe. There is nothing like seeing smoke roll out of your favorite Boogie, and I know from experience. :roll:

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