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  #21  
Old 02-13-2014, 04:56 AM
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Quote:
Originally Posted by chops-tube View Post
Yep. Fuses don't blow for no reason at all. Something is causing too much current draw - a.k.a. - bad tube somewhere. Did you notice if any of the tubes had plates glowing orange/red? I had some 6L6's and 300B's do that, but it didn't phase the amps one bit luckily.
Charles, I've looked at them carefully and checked the bias and I didn't notice anything wrong. One has a slight blue hue but I read that it was normal.

Anyway I don't trust them anymore.

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Originally Posted by chops-tube View Post
I had a pair of 5U4's that rattled in an old amp that I overhauled for one of my brothers. I replaced them with some RCA 5U4 GT's (used narrower, taller plates) and the rattle went away.
I know you're right because the rattling has changed side ! I need to try to see if it's coming from the output tube or the driver. I'll make some tests

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Originally Posted by chops-tube View Post
I had some EH 6CA7's for an old Consonance M-100 SE I had years ago. They sounded better than any of the EL34's and KT88's I tried regardless of being new or NOS.

On a side note, I've always felt that if you're going to own tube gear, it would be a good idea to invest in a decent solid state tube tester. I have one, though no tube gear now. Go figure. LOL
Matt has told me by PM that Manley says to use 12AX7 with the 6CA7. I don't know if it can damage anything if I use the 12AT7 that are currently installed.

I'm just a beginner with tubes so I'm learning along.
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  #22  
Old 02-15-2014, 10:10 PM
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Originally Posted by antipop View Post
Matt has told me by PM that Manley says to use 12AX7 with the 6CA7. I don't know if it can damage anything if I use the 12AT7 that are currently installed.

I'm just a beginner with tubes so I'm learning along.
That's odd. I've used those 6CA7's in the said Consonance amp as well as a Cary SLi-80 and never swapped out the 12AX7's when going back to EL34's. In fact, both amps used 12AX7's with KT88's as well. All that was needed was a re-bias obviously.

Both EL34 and 6CA7 are virutally identical power pentodes whereas the KT88 is a beam tetrode.

The 12AX7 is a hi Mu tube (high gain) and the 12AT7 is a lo Mu (low gain). Then of course there's the 12AU7 which is a medium Mu, or as you guessed it, (medium gain).
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  #23  
Old 02-16-2014, 02:12 AM
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Georges,

With the 6CA7 tubes, I have other input tubes. They go together.
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  #24  
Old 02-16-2014, 05:00 AM
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As far as I understand it, despite being marketed as identical / drop in replacements, there are minor differences between EL34's and 6CA7's.....this is copied from another forum, chap explains it much better than I can, I'm no technician lol!!

"Technically speaking, the old production, US made "fat bottle" 6CA7s are beam tetrodes in that they have only two grid windings. Beam forming plates take the place of g3. They look somewhat like healthy 6L6GCs and the beam forming plates are plainly visible if you you look close. AFAIK, only GE and Sylvania/Philips ECG made these although they were rebranded by others. They're very rugged and apparently have a following in the guitar world. There are current versions being mfgd by Sovtek and others and these too are beam tetrodes.

EL34s are true pentodes in that they have three grid windings and no beam forming plates. They're almost always in tall, smaller diameter bottles compared to 6CA7s. True pentode EL34s have been mfgd just about everywhere but the US."

I have only had EL34's in my Snappers so it's never been an issue, but as I spotted it on Manley's Snapper page, thought I'd pass it on
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  #25  
Old 02-16-2014, 03:10 PM
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Quote:
Originally Posted by chops-tube View Post
That's odd. I've used those 6CA7's in the said Consonance amp as well as a Cary SLi-80 and never swapped out the 12AX7's when going back to EL34's. In fact, both amps used 12AX7's with KT88's as well. All that was needed was a re-bias obviously.

Both EL34 and 6CA7 are virutally identical power pentodes whereas the KT88 is a beam tetrode.

The 12AX7 is a hi Mu tube (high gain) and the 12AT7 is a lo Mu (low gain). Then of course there's the 12AU7 which is a medium Mu, or as you guessed it, (medium gain).
Quote:
Originally Posted by magoo View Post
As far as I understand it, despite being marketed as identical / drop in replacements, there are minor differences between EL34's and 6CA7's.....this is copied from another forum, chap explains it much better than I can, I'm no technician lol!!

"Technically speaking, the old production, US made "fat bottle" 6CA7s are beam tetrodes in that they have only two grid windings. Beam forming plates take the place of g3. They look somewhat like healthy 6L6GCs and the beam forming plates are plainly visible if you you look close. AFAIK, only GE and Sylvania/Philips ECG made these although they were rebranded by others. They're very rugged and apparently have a following in the guitar world. There are current versions being mfgd by Sovtek and others and these too are beam tetrodes.

EL34s are true pentodes in that they have three grid windings and no beam forming plates. They're almost always in tall, smaller diameter bottles compared to 6CA7s. True pentode EL34s have been mfgd just about everywhere but the US."

I have only had EL34's in my Snappers so it's never been an issue, but as I spotted it on Manley's Snapper page, thought I'd pass it on
Thank you to both of you, that's very informative.

I understand that I can use the AX/AT/AU without any damage to the amps. It's just that some are better adapted to the tubes selected.
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  #26  
Old 02-16-2014, 03:10 PM
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Quote:
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Georges,

With the 6CA7 tubes, I have other input tubes. They go together.
Of course you do You're a real mine
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  #27  
Old 03-23-2014, 09:52 AM
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I had the same thing happening this morning but on the other block.

The odd thing is that I played music all day long yesterday. The block must have been on for like 8 hours. The last time it happened it was the exact same thing. I don't know if there is a link there.

I don't think the tube are faulty this time. They are brand new Winged C and last time I was using the PSVane. It could also be the voltage as it can go as high as 240V here and it's not unusual to have 237V over a long period.
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  #28  
Old 03-23-2014, 10:30 AM
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Georges,

I just saw the thread and was sad to hear you were having this trouble. Although I have a tube preamp and amp, this "old" technology is totally new to me so I have no idea what could be wrong. I did do a search and found some information on another forum about a similar problem with Manley Snappers, where it was attributed to "defective/dying/leaking electrolyte cap in BIAS supply".

One thing I like about McIntosh tube gear is that they have been doing this for many years, and I am especially thrilled that the company was founded in my great state of Maryland, not New York, which everyone equates with McIntosh nowadays. Anyhow, I felt secure that--knock on wood--most of the issues would have been worked out with the technology over the years. In any case, I am so glad that I will have new tubes soon; mine are stock and I have been running them (not too hard) for the last 2.5 years. I am afraid something like what you experienced is slowly creeping up on me.

Anyhow, when you visit and listen to my McIntosh gear, you might consider coming over to the Mac side of the aisle. We can, of course, visit the Mac store, KSSONS, in the Paragon, too. So why don't you leave the speaker at home this time and save space to return with a MC275?
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  #29  
Old 03-23-2014, 10:37 AM
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Thank you Ron, you're right maybe I should email Manley about that.

Though when I opened them I couldn't see anything wrong inside.

Don't tempt me with that MC275, it is one of the best looking amp and I've never had the chance to listen to it. That will change when I visit you.

The Air Tight is also wonderful looking and I've heard good things about it.
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  #30  
Old 03-23-2014, 11:32 AM
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The Air Tight is also wonderful looking and I've heard good things about it.
Georges, I don't know what Air Tight is.

Off to bed now
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